JP2012073397A - Three-dimentional map display system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To display a map in which characters have perspective.SOLUTION: A three-dimensional map display system displays a map by perspective projection based on three-dimensional polygon data of features such as a road and a building. As for characters displayed in the map, the size of characters is changed according to the depth of an object to be indicated by the characters, such as a building. In the perspective projection, while a building and the like are displayed in reduced sizes according to their depths, the size of characters is changed at a display ratio different from that applied to a building and the like. Thus, characters themselves can have perspective, facilitating intuitive grasping of the relationship between the characters and the building or the like. By applying a different display ratio from that of the perspective projection, it is possible to avoid a too large or too small character size and achieve an easily readable character expression.

Description

  The present invention relates to a three-dimensional map display system for drawing a three-dimensional map in which features are three-dimensionally expressed, and more particularly to a method for representing characters on a three-dimensional map.

There is a three-dimensional map display system that three-dimensionally displays features such as buildings and roads by perspective projection when displaying an electronic map on a screen of a navigation device, a computer, and a portable terminal. In the 3D map display system, 3D polygon data representing buildings and roads is stored as map data, and processing called rendering is performed in accordance with the specified viewpoint and line-of-sight vector such as the current position of the user. The map is drawn by perspective projection.
Patent Document 1 discloses a technique for displaying names of buildings and the like in characters on such a three-dimensional map. In this technique, character data is prepared separately from polygon data, and characters are arranged in a two-dimensional image in which a building or the like is drawn by perspective projection. The arrangement of characters is determined so that a display area corresponding to a silhouette of each building or the like is obtained and the characters are contained within the display area.
Patent Document 2 discloses a technique for displaying characters in a three-dimensional CAD, although it is a field different from a map. In this technology, a character is displayed by arranging the character in a three-dimensional space for modeling the object and perspectively projecting the character together with the model of the object.

JP 2003-263102 A JP-A-63-136174

FIG. 1 is an explanatory view showing a display example of characters in the prior art. Conventionally, when displaying characters on a three-dimensional map, all names have been displayed with the same character size and character spacing.
When displayed in this way, as can be seen from FIG. 1, if many characters are arranged in the map, the perspective cannot be grasped from the characters themselves, so which building or the like each character points to Difficult to grasp intuitively. In addition, since characters indicating a distant building or the like are also displayed in a relatively large size, there is a problem that the screen becomes complicated.
In view of such problems, an object of the present invention is to realize a character display on a three-dimensional map that makes it easy to intuitively understand the correspondence between a drawn feature such as a building and a character.

The present invention can be configured as a three-dimensional map display system that draws a three-dimensional map that represents a feature three-dimensionally. The three-dimensional map display system of the present invention includes a map database, a background drawing unit, and a character display unit.
The map database stores three-dimensional polygon data and character data. Other data such as road network data for performing route guidance may be stored together.
The three-dimensional polygon data is data for drawing a feature three-dimensionally by a perspective projection method. Such an image drawn three-dimensionally may be hereinafter referred to as a background image or a map image. The features refer to various objects arranged on the ground such as buildings, traffic lights, guide boards, bridges, roadside trees, roads, mountains, rivers, seas, and the like.
Character data is data for specifying a character string and a display position for displaying a predetermined name in a background image. Examples of names to be displayed include names of features, intersection names, place names, addresses, street names, destination guidance, and the like. Each character data is stored in association with a feature to be displayed or a point to be displayed in order to specify a display position. Further, as character data, attributes such as a font of a character to be displayed, a character color, and vertical / horizontal writing may be stored together.
The background drawing unit generates a background image by drawing a feature three-dimensionally by perspective projection using the three-dimensional polygon data.
The character display unit displays characters representing a predetermined name in the background image using character data. The character display unit displays a character string of each name so that a character frame that encloses the character string becomes smaller according to the depth from the viewpoint in the perspective projection method. However, the display ratio according to the depth is set to be different from the display ratio in the perspective projection method. The display ratio refers to the ratio of the size of the character frame at each depth to the size of the character frame at a predetermined reference position.
The character frame can typically be a rectangle having the maximum width and height of the character string, but various shapes that are uniquely determined according to the character string can be defined as the character frame. In order to reduce the character frame, at least one of the character size and the character spacing of the character string is changed according to the depth. Only the character size may be changed, or only the character spacing may be changed. Further, both the character size and the character spacing may be changed. Further, both the character size and the character spacing may be switched and changed such that only the character spacing is changed in a foreground with a depth within a predetermined range, and the character size is changed in a distant view beyond the depth.

According to the three-dimensional map display system of the present invention, as described above, the size of the character frame can be changed and displayed according to the depth. That is, even if the same character string is displayed in a distant view far from the viewpoint, the character frame is displayed to be smaller than that displayed in the close view. By determining the character size and the character spacing in this way, it is possible to give the character a sense of perspective, and it becomes easier to intuitively understand the correspondence between the character and the feature.
In perspective projection, distant features and the like are displayed at a reduced display ratio corresponding to the depth compared to near-view features and the like. However, in the present invention, characters are different from the display ratio of features and the like. Apply the display ratio. In this way, the character display ratio can be set flexibly, the perspective of the character can be given, and the character can be easily read.

Various settings can be made for the display ratio of the character frame. For example, the size of the character frame may be changed at a display ratio larger than that of the perspective projection method when the depth is within a predetermined value or less. In this way, even if the depth increases within this range, the character frame can be displayed relatively large compared to the buildings being reduced, so that the characters can be displayed in a legible manner. , The usefulness as a map can be improved.
The display ratio of the characters may be changed linearly according to the depth or may be changed in a curve.
In general, in the perspective projection method, when the depth is taken on the horizontal axis and the display ratio is taken on the vertical axis, the graph becomes an inversely proportional graph asymptotically approaching “display ratio = 0”. It is sufficient that the character display ratio is set to be larger than the inversely proportional graph within a range where the depth is equal to or less than a predetermined value. The range below the predetermined value can be set, for example, within a depth range where characters can be displayed in a legible manner.

In the character display, a character positioned within a predetermined depth range from the viewpoint position may be displayed. That is, characters that are deeper than this range may be excluded from display. By doing so, it is possible to avoid displaying characters that are so small that they cannot be read and to avoid complication of the map screen.
Various settings can be made for the predetermined range. For example, a circular area within a predetermined radius from the viewpoint position may be displayed. In addition, a band-like region or a rectangular region having a straight line that is a predetermined distance away from the viewpoint position in the depth direction as a boundary may be displayed.

  At least one of the character size and the character spacing may be changed within a preset limit range. Only one of the maximum value / minimum value may be provided as the limit value, or both may be provided. If the maximum value of the character size is provided, it is possible to avoid a situation in which characters are excessively large and an image such as a feature is obscured. By providing a minimum character size, it is possible to avoid displaying characters that are too small to be legible. If the maximum value of the character spacing is provided, it can be avoided that the character spacing is too wide to be recognized as a series of character strings. If the minimum value of the character spacing is provided, it is possible to avoid clogging of characters so that they cannot be recognized as individual characters. By providing these limit values in this way, easy-to-read character display can be realized.

Different display ratios may be applied to the vertically long character frame and the horizontally long character frame. There is a difference in legibility between vertically long character frames (vertically written characters) and horizontally long character frames (horizontal characters). It is possible to realize easy-to-read character display.
The display ratio applied to each of the vertically long character frame / horizontal character frame can be set in various ways. For example, when the map display screen is rectangular, the character frame in the direction along the long side A display ratio that is steeper than the character frame in the direction along the short side may be applied. In the case of a rectangle having a long side and a short side, the display ratio that is steeper than the vertically long character frame along the short side is applied to the horizontally long character frame along the long side. Since a plurality of character frames in the direction along the long side are arranged shifted in the short side direction, the distance between the character frames tends to be narrowed. Can be suppressed.
In order to reduce the complexity of character display, as another mode, a character size that is smaller than a vertically long character frame may be used. In this way, even if a display ratio common to the portrait and landscape is applied, complexity in the screen can be suppressed.

In the present invention, the character display unit may determine whether or not to display characters by the following method.
First, the character display unit specifies the features to be displayed and the outline of the background as the character display area. Then, when the maximum width of the display area is larger than the width of the character frame, the character is displayed. By doing this, characters that fit within the display area at least in the width direction are to be displayed, so unnecessary characters for features that are only partially visible can be excluded from display. Can be suppressed.
If the size of the character frame is to be displayed at a fixed size, the perspective projection method displays the feature, etc., as it is distant from the distant view, so that the character frame immediately protrudes from the display range of the feature, etc. Therefore, the determination of whether or not display is possible by the above-described method is not effective. In the present invention, since the character frame is changed according to the depth, it is possible to selectively display a meaningful character to be displayed by the above-described method.

For example, the following method can be used for character arrangement when displaying characters.
First, a character display part sets the display position of the character in the drawn map by several methods. And the display position with few overlaps of the character frame of a character and another character is selected from the set several display positions. By doing so, it is possible to avoid easy overlapping of characters and realize easy-to-read character display.

Moreover, in this invention, you may make it display the destination of each exit direction about an intersection. For example, the destination when turning right at the intersection and the destination when turning left are displayed. Such a display can be realized, for example, by the following method.
First, the map database is provided with a destination database that stores character strings representing destinations in the exit directions of the intersections in association with the directions of entry into the intersections for the intersections in the map. This database can take various structures. For example, using the network data expressing roads as nodes and links, for each combination of a link entering the intersection and a link corresponding to the exit of the intersection, A mode of storing a destination can be taken. Then, the character display unit specifies the approach direction or the approach link based on the line-of-sight vector in the perspective projection method or the current position and the traveling direction, and specifies the link corresponding to each exit direction, thereby specifying the destination database described above. It refers to it and displays characters that indicate the destination.
This makes it possible to display the destination guidance relatively easily. The street name corresponding to the exit direction may be stored in the destination database, and the street name may be displayed together with the destination or instead of the destination.
The destination guidance need not be displayed for all intersections, but may be displayed only for some intersections such as the nearest intersection.

  The present invention may be configured as a 3D map display method for drawing a 3D map by a computer, or as a computer program for causing a computer to execute such drawing. Moreover, you may comprise as a computer-readable recording medium which recorded such a computer program. Recording media include flexible disks, CD-ROMs, magneto-optical disks, IC cards, ROM cartridges, punch cards, printed matter on which codes such as bar codes are printed, computer internal storage devices (memory such as RAM and ROM), and A variety of computer-readable media such as an external storage device can be used.

It is explanatory drawing which shows the example of a character display in a prior art. It is explanatory drawing which shows the structure of the three-dimensional map display system in an Example. It is explanatory drawing which shows the example of a character display in an Example. It is a flowchart of a route guidance process. It is a flowchart of a three-dimensional map display process. It is a flowchart of a character size determination process. It is explanatory drawing which shows the other example of a setting of a character display object area | region. It is explanatory drawing which shows the setting example (1) of a character size. It is explanatory drawing which shows the example (2) of a character size setting. It is explanatory drawing which shows the example (3) of a character size setting. It is a flowchart of a character arrangement process. It is a flowchart (1) of an intersection and a destination display. It is a flowchart (2) of an intersection and a destination display. It is explanatory drawing which illustrates a destination database. It is explanatory drawing which shows the destination display example.

<< System configuration >>
FIG. 2 is an explanatory diagram illustrating the configuration of the three-dimensional map display system in the embodiment. FIG. 2 shows a configuration example as an in-vehicle car navigation device. The three-dimensional map display system may be configured as a navigation device for pedestrians. The three-dimensional map display system 100 is not limited to the configuration as an in-vehicle device, but includes a mobile phone, a PDA (Personal Digital Assistant), a PND (Personal
It is also possible to configure using a portable terminal such as a navigation device. The 3D map display system 100 does not necessarily have a navigation function, and may be configured as a system that simply displays a 3D map.

  The three-dimensional map display system 100 includes a main body including a display 101, a switch 102, and the like. By operating the switch 102 in accordance with a menu or the like displayed on the display 101, the user can designate a route search condition such as a departure place, a destination, time priority / distance priority. Further, a map and a route are displayed on the display 101 during route guidance. On this screen, by operating the switch 102, switching between north up (display where the top of the map is north) / heading up (display where the top of the map is the moving direction of the moving body) and the display size of the map Switching, switching between three-dimensional display / two-dimensional display, and the like can be performed.

In the upper part of the figure, functional blocks provided in the three-dimensional map display system 100 are shown. In this embodiment, the three-dimensional map display system 100 includes a microcomputer having a CPU, a ROM, and a RAM inside, and each functional block in the figure is mainly implemented by software according to a control program provided in the ROM. It is configured. Each of these functional blocks may be configured in hardware.
Further, in this embodiment, the apparatus configuration that operates stand-alone by providing all the functional blocks necessary for the three-dimensional map display system 100 is adopted. On the other hand, at least a part of the functions in the figure may be provided by a server connected to the 3D map display system 100 via a communication line such as a network.

  The three-dimensional map display system 100 is provided with a map database 130 used for route search and route guidance. In addition to being stored in the 3D map display system 100, the map database 130 may be provided by a recording medium such as a DVD, or may be supplied from a server via a communication line such as a network.

The map database 130 includes road network data 131, three-dimensional polygon data 132, and character data 133.
The road network data 131 is a network in which roads are represented by nodes and links, and is mainly used for route search and route guidance. A link is a line segment or a broken line composed of a sequence of points represented by position coordinates corresponding to a road. A node is a point represented by position coordinates corresponding to an intersection or end point of a link.
The three-dimensional polygon data 132 is data for displaying a three-dimensional map in which features and the like are three-dimensionally displayed. The three-dimensional polygon data 132 stores data for displaying information boards, road signs, guardrails, street trees, etc. existing around the road in addition to data on elevated roads, buildings and other structures. Can reproduce almost the same screen as the sight actually seen.
The character data 133 stores data for displaying various characters in the map, such as names of features, intersection names, place names, addresses, street names, and the like. The character data 133 is stored in association with features to be displayed. For names where there is no 3D polygon data to be displayed, such as intersection names and place names, the display position may be specified in a coordinate system such as latitude and longitude. The character data 133 may also store attributes such as the font of the character to be displayed, the character color, and vertical / horizontal writing.

The main control unit 110 integrally controls the operation of the 3D map display system 100. The command input unit 115 inputs commands such as route search condition designation and route guidance display switching through the operation of the switch 102 by the user.
The route search engine 112 performs a route search with reference to the road network 131 according to the conditions specified by the user. As a route search method, for example, a well-known Dijkstra method can be used. The route search result 113 is a memory area for storing a route search result. The result of the route search can be stored in an arbitrary format. In the present embodiment, the nodes and links to be passed are stored in the form of a node-link sequence that is sequentially designated.
The GPS 111 detects the current position by the Global Positioning System. The detection accuracy can also be improved by using the detection result by the gyro in combination.
The route guidance unit 114 displays a route guidance screen stored in the route search result 113 on the display 101 according to the detected current position. The guidance screen includes a screen displaying a route on a two-dimensional map and a screen using a three-dimensional model. Three-dimensional display from various viewpoints such as bird's eye view and driver's view is possible. The viewpoint of the three-dimensional display can be automatically switched according to the positional relationship with the intersection as well as being switched by the user's operation.
The display control unit 120 controls display on the display 101. Examples of display contents include display of a menu screen for designating route search conditions and the like, and display of a map used for route search and route guidance.
The display at the time of route guidance by the three-dimensional map is performed by the background drawing unit 121, the character display unit 122, and the route display unit 123 shown in the figure. The background drawing unit 121 draws a feature or the like by the perspective projection method using the three-dimensional polygon data 132. The character display unit 122 displays characters such as names of features in the drawn background image. The route display unit 123 refers to the route search result 113 and displays the route in the background image. In this embodiment, the drawing and display are performed separately from the layer for drawing the background image, the layer for displaying characters, and the layer for displaying the route. The entire 3D map may be drawn with one layer, or more layers may be used. The layers may be overlapped in an order other than that shown in the figure.
The 3D map display system 100 can also simply display a 3D map regardless of route guidance. In such a case, the background drawing unit 121 and the character display unit 122 are used.

<< Example of character display >>
FIG. 3 is an explanatory diagram illustrating an example of character display in the embodiment. In the order of FIG. 3 (a) to FIG. 3 (d), the display at the time of traveling on the road “Hundred Years Bridge” located in front is shown.
Focusing on the character “Rubie Hakata” shown in a circle in the figure, it corresponds to the character frame of this character string, that is, the outline of the character “Rubie Hakata” in the order of FIG. It can be seen that the size of the rectangle to be increased. In the present embodiment, the character is displayed by changing the size of the character frame according to the depth as described above.
Specifically, in the state of FIG. 3A, the building “Rubie Hakata” is farther in the depth direction than the viewpoint position, and thus is drawn smaller by the perspective projection method. Therefore, the name “Rubie Hakata” is also displayed small. As shown in FIG. 3B to FIG. 3D, when approaching “Rubie Hakata”, the building is gradually drawn larger by the perspective projection method, so that the name is also displayed gradually larger.
In the example of FIG. 3, an example is shown in which both the character size and the character spacing are changed according to the depth. However, only one of the character size or the character spacing may be changed. A method for setting the character size and the like according to the depth will be described later.
As is apparent from a comparison between the display example in the prior art (FIG. 1) and FIG. 3, by changing the size of the character frame according to the depth, the character itself can be given perspective. There is an advantage that it is easy to intuitively understand the correspondence between characters and buildings. Moreover, the complexity in the map can be suppressed by displaying the characters in the distant view small.
Hereinafter, a technique for displaying a three-dimensional map by changing the size of a character frame as shown in FIG.

<< Route guidance processing >>
FIG. 4 is a flowchart of route guidance processing. This is a process executed by the CPU of the 3D map display device 100. When the process is started, the CPU sets a starting point and a destination for route search (step S10). The departure point may be designated by the user, or the current position detected by the GPS 111 may be used.
When the starting point and destination are set, the CPU searches for a route (step S12). The route search can be performed by a known Dijkstra method with reference to the road network data 131, for example. The obtained route is accumulated in the route search result 113.
The CPU obtains the current position and the traveling direction based on the detection result of the GPS 111 and the change thereof (step S14), and performs route guidance while displaying the three-dimensional map (step S100). In this embodiment, the map display can be switched between a two-dimensional map and a three-dimensional map. Here, a case where a three-dimensional map display is performed will be described as an example. This route guidance is continuously performed until the destination is reached (step S500).
In the present embodiment, an example in which a 3D map is displayed as a process of route guidance processing is shown, but it is also possible to display a 3D map simply according to a user operation regardless of route guidance.

<< 3D map display processing >>
FIG. 5 is a flowchart of the three-dimensional map display process. This process corresponds to step S100 in FIG.
In this embodiment, as shown on the right side of FIG. 5, drawing is performed separately for a background layer, a character layer, and a route layer. The background layer is a layer for drawing a background image such as a feature. The character layer is a layer for displaying characters such as names of features. The route layer is a layer for displaying a route search result with an arrow or the like. On the display 101, an image obtained by superimposing these layers is displayed.
When the 3D map display process is started, the CPU performs a background drawing process (step S200). This is a process of drawing a feature or the like by a perspective projection method with reference to the three-dimensional polygon data 132. As the perspective of the perspective projection method, a current position or a position shifted by a predetermined distance from the current position can be used. The current traveling direction can be used as a line-of-sight vector for perspective projection. The user may be able to specify the viewpoint and line-of-sight vector.
Next, the CPU performs a character display process (step S300). This is a process for displaying characters such as names of features displayed in the map. As shown in FIG. 3, in this embodiment, since the size of the character frame is changed by changing the character size according to the depth of the feature or the like that is the target of the character display, the CPU responds to the depth. Processing for determining the character size, that is, character size determination processing is performed (step S310). Then, after determining the character size, processing for determining character placement, that is, character placement processing is performed (step S340). Further, a process for displaying the name of the intersection and a destination for the exit from the intersection, that is, an intersection / destination display process is performed (step S370). Details of these processes will be described later.
When the background and characters are displayed in this way, the CPU performs a route display process (step S400). This is a process of referring to the route search result 113 and displaying a route toward the destination with an arrow or the like.

<< Character size determination process >>
FIG. 6 is a flowchart of the character size determination process. This is processing corresponding to step S310 in FIG.
The CPU acquires the current position Pv (step S312). Then, the center of gravity position Pobj of the feature represented by the character to be processed is acquired (step S314). Since the character data 133 is stored in association with the three-dimensional polygon data 132 to be represented by the characters, the gravity center position Pobj can be acquired by referring to the three-dimensional polygon data 132. For characters that are not associated with features such as intersection names, street names, and place names, the position to be displayed is stored in the character data 133, so that this position can be used as the above-described center-of-gravity position Pobj. .
The CPU acquires the distance d between the viewpoint position and the center of gravity position as shown in the upper right explanatory diagram in the figure (step S316). Then, it is determined whether or not the distance d is within the specified range Dc from the viewpoint (step S318). As shown in the explanatory diagram in the lower right of the figure, a circular area A having a radius Dc is set with the viewpoint Pv as the center, and it is determined whether or not the center of gravity position Pobj of the feature represented by the characters is within this circular area A. It will be.
If the distance d to the center of gravity position Pobj is smaller than the specified distance Dc (step S318), the character size corresponding to the distance d is determined (step S322). The character size is determined based on a function set in advance according to the depth. A specific determination method will be described later. When the center of gravity position Pobj is deviated from the line-of-sight vector, although the distance d is strictly different from the depth, the character size may be determined by regarding the distance d as the depth. Since the angle of view in the left-right direction of the 3D map is limited, characters at positions far from the line-of-sight vector in the left-right direction deviate from the angle of view, and characters at positions shifted to the left and right are shades of other buildings. This is because there are many characters near the line-of-sight vector.
In step S318, if the distance d is greater than the specified distance Dc, the character is excluded from display (step S320). That is, only the characters corresponding to the features located in the circular area A shown in the figure are to be displayed, and the characters located outside thereof are not to be displayed. In this way, by using only characters within a certain distance from the viewpoint Pv as display targets, it is possible to thin out characters that are far away, and avoid the complication of the map image.
The distance Dc that defines the circular area A is a distance that is a criterion for determining whether or not to display characters, and can be arbitrarily set. If the distance Dc is increased, a large number of characters become display targets, so that information provided on the map increases, but the map image tends to become complicated. Conversely, if the distance Dc is reduced, the map image has fewer characters and is concise, while the information provided by the map is reduced. The distance Dc may be set in consideration of both. The distance Dc may be fixed in advance or may be specified by the user.

In FIG. 6, after the character to be processed is determined, the center of gravity position Pobj where the character is to be displayed is obtained, and it is determined whether or not the character is to be displayed depending on whether or not it belongs to the circular area A ( An example is shown in which processing is performed in the procedure of step S313).
Whether or not to be a display target can be determined by various processing methods. Contrary to the method shown in FIG. 6, first, a circular area A centering on the viewpoint position Pv is set, an object in the circular area A is extracted, and character data corresponding to the circular area A is selected. May be specified. Since only characters that are present in the line-of-sight vector direction are a problem in displaying characters, a method of specifying a character to be displayed using a semi-circular area obtained by cutting the circular area A with a diameter orthogonal to the line-of-sight vector is used. You can also.

Although FIG. 6 shows an example in which the character to be displayed is discriminated using the circular area A, it may be judged using an area other than the circle.
FIG. 7 is an explanatory diagram illustrating another setting example of the character display target area. In this example, a rectangular area is used as the character display target area. Assuming that the viewpoint position Pv and the line-of-sight vector Vv are used, when the projection distance dd in the line-of-sight vector direction from the viewpoint position Pv to the object is within the specified distance Dr, the character is determined to be a display target. For the projection distance dd, the perpendicular foot PH from the center of gravity position Pobj of the object to the line-of-sight vector Vv may be calculated, and the distance from the viewpoint Pv to the foot PH may be calculated.
Furthermore, the width direction orthogonal to the line-of-sight vector may be limited. As shown in the figure, only the width Wr is displayed. The width Wr can be arbitrarily set in consideration of the angle of view of the perspective projection method. By doing so, it is possible to further thin out characters to be displayed. Compared with the circular area shown in FIG. 6, when the rectangular area is used, the prescribed distance Dr and the width Wr in the direction of the line-of-sight vector Vv can be set individually, so that the character display target area can be flexibly set. There is an advantage that can be set.

Next, the method for determining the character size in step S322 in FIG. 6 will be described.
FIG. 8 is an explanatory diagram showing a setting example (1) of the character size. A straight line Ls in FIG. 8A represents the relationship between the character size and the distance from the viewpoint, that is, the depth. As shown in the drawing, in this embodiment, the display ratio decreases linearly from the maximum value Smax to the minimum value Smin as the depth increases. The display ratio is set within a range where the depth is smaller than Dmax. This is because characters are not displayed in a range exceeding the maximum depth value Dmax, and this Dmax value corresponds to the radius Dc of the circular area A in FIG. 6 or the side Dr of the rectangular area in FIG. The display ratio is set to be a minimum value at a depth Dlim smaller than Dmax. Therefore, between the depths Dlim and Dmax, the display ratio is a minimum value and a fixed value regardless of the depth. By providing a range that is a fixed value in this way, it is possible to avoid characters being too small and display characters of a readable size.
In general, in the perspective projection method, when the depth is taken on the horizontal axis and the display ratio is taken on the vertical axis, the display ratio Lp is an inversely proportional graph asymptotically approaching “display ratio = 0”. In this embodiment, the character display ratio Ls is set to be larger than the display ratio Lp in the perspective projection method. In perspective projection, the building is reduced and displayed as the depth increases. However, by setting the character display ratio as shown in FIG. 8A, characters are displayed at a slower rate than the building as the depth increases. The size becomes smaller. Therefore, it is possible to prevent the character size from becoming too small, and it is possible to display characters in a legible size.
In the present embodiment, the character interval is defined as the interval between the lower end of the upper character and the upper end of the lower character. Therefore, if the character size is changed, the size of the rectangular character frame circumscribing the character string changes both vertically and horizontally according to the character size even if the character spacing is constant.
Although FIG. 8A shows an example of setting the display ratio of the character size, a graph that sets the character size according to the depth may be used instead.

FIG. 8B is an explanatory diagram showing a display example of characters according to the setting of FIG. A display example when the display position of the character string “ABCDE Building” is changed in the depth direction is shown. A rectangle Cb that includes this character string is a character frame. However, in order to avoid complication of the figure, for each character, a rectangle obtained by enlarging the character frame Cb at a certain ratio is drawn as a character frame.
As illustrated, the character size gradually decreases as the depth increases. The fact that the display ratio is linear is understood from the fact that the upper and lower ends of the character frame of “ABCDE Building” are arranged linearly. When the character size is changed at the same display ratio as in the perspective projection method, the straight line connecting the upper end and the lower end should intersect at the vanishing point Vp. In the example of FIG. The lines connecting are crossed at points different from the vanishing point Vp. From this, it can be seen that the display ratio of characters at each depth is larger than the display ratio by the perspective projection method.

  FIG. 8C is a display example of characters in the map. As shown in the figure, characters for a distant building such as “Rubie Hakata” are displayed smaller than characters for a building in the foreground such as “Nishitetsu Building Annex”. By doing so, it is possible to grasp the perspective from the characters and to easily understand the correspondence between the characters and the building intuitively.

The change of the character size can be variously set as shown in FIG.
FIG. 9 is an explanatory diagram showing a setting example (2) of the character size. A curve Cs in FIG. 9A represents the relationship between the display ratio and the distance from the viewpoint, that is, the depth. As shown in the drawing, as the depth increases, the display ratio decreases in a curve so as to gradually approach the minimum value Smin from the maximum value Smax. The display ratio is set within a range where the depth is smaller than Dmax, as in FIG. As such a curve, various functions such as an exponential function and a hyperbola can be used. When a curve asymptotic to the minimum value Smin is used, the display ratio is approximately close to the minimum value Smin in the vicinity of the maximum value Dmin, and there is an advantage that it is possible to easily avoid that the characters become too small with one unified function. is there.
Various functions can be set for the function of the curve, but it is preferable to set the function so that the display ratio is larger in the entire range than the display ratio Lp by the perspective projection method. By doing so, the change in the character size can be made gentler than the change in the size of the building, and the character size can be prevented from becoming excessively small.

FIG. 9B is an explanatory diagram illustrating a display example of characters according to the setting of FIG. A display example when the display position of the character string “ABCDE Building” is changed in the depth direction is shown. As shown in the figure, it can be seen that the character size gradually decreases as the depth increases. The fact that the display ratio is curvilinear can be understood from the fact that the upper end is arranged in a curved line when the lower end of the character string “ABCDE Building” is arranged linearly. The reason why the lower ends are arranged linearly is that the lower ends of the buildings are arranged linearly along the road, and it is less uncomfortable to arrange the characters according to this.
In the example in the figure, the straight line connecting the lower ends of the characters intersects at the vanishing point Vp, whereas the curve connecting the upper ends goes to a point different from the vanishing point Vp. It can be seen that the display ratio is larger than

  FIG. 9C is a display example of characters on the map. As shown in the figure, characters for a distant building such as “Rubie Hakata” are displayed smaller than characters for a building in the foreground such as “Nishitetsu Building Annex”. By doing so, it is possible to grasp the perspective from the characters and to easily understand the correspondence between the characters and the building intuitively.

The character size can be further variously set.
FIG. 10 is an explanatory diagram of a display ratio setting example (3).
FIG. 10A shows a modified example of the setting for changing the display ratio linearly. In this example, the display ratio is determined according to the three categories as follows.
Depth <D0 ... The display ratio is fixed at the maximum value Smax;
D0 ≦ depth ≦ Dlim... Display ratio changes linearly from the maximum value Smax to Smin;
Dlim <depth ≦ Dmax .. The display ratio is fixed at the minimum value Smin;
As described above, a range in which the display ratio is constant may be provided also in a foreground portion where the depth <D0. By doing so, there is an advantage that it is possible to prevent the characters in the foreground from becoming excessive and protruding from the screen.

FIG. 10B shows a modified example of the setting for changing the display ratio in a curved manner. The display ratio is changed from the maximum value Smax by a combination of an upwardly convex curve and a downwardly convex curve so that the depth Dmax becomes the minimum value Smin as in the curve Cs1. An example of such a function is a cosine function. By doing so, it is possible to suppress characters from becoming excessively small in the foreground while suppressing characters from becoming excessively small in the foreground, and to display readable characters throughout.
As another setting example, the curve may be changed from the maximum value Smax to the minimum value Smin by a curved line that protrudes upward like the curve Cs2. As such a curve, an exponential function, a sine function, or the like can be used. By doing so, the character size is abruptly reduced toward the distant view, so that it is possible to avoid an excessive amount of characters in the foreground and to display a map with an emphasis on providing information in the foreground.

Although the method for setting the character size has been described with reference to FIGS. 8 to 10, the character spacing may be similarly changed according to the depth. When the character spacing is defined by the distance between the representative points of each character, it is preferable to change the character spacing. In such a definition, even if the character size is reduced, the distance between the representative points of the characters does not change, so that a gap between the characters is opened. Regardless of the definition of the character spacing, if the character spacing is changed in accordance with the change in the character size, the entire character string can be displayed in a well-balanced manner in both the distant view and the near view. The change in character size and the change in character spacing may be different display ratios, or the same display ratio may be applied.
8 to 10 show examples in which the character size is changed. However, since the perspective can be grasped if the size of the character frame changes, the character size is fixed and only the character spacing is set to the depth. It is good also as a setting changed according to. Furthermore, when the depth is within the predetermined range, only the character spacing is changed, and when the depth is larger than the predetermined range, the character size alone or the character size and the character spacing is changed. You may switch.

  8 to 10 show settings for a vertically long character frame. For horizontally long character frames, settings similar to those for vertically long may be applied, or different settings may be used. As shown in FIG. 3C, the horizontally long character frames are arranged so as to be shifted in the vertical direction according to the depth, and therefore the space between the character frames tends to be narrower than that of the vertically long character frames. Therefore, it is preferable to apply a setting in which a character size is relatively smaller than a horizontally long character frame.

<< Character placement processing >>
FIG. 11 is a flowchart of the character arrangement process. This is a process for determining the arrangement in the map image for the character whose size has been determined, and is a process corresponding to step S340 of the character display process (FIG. 5).
When the process is started, the CPU acquires the horizontal width Wobj of the object (step S342). An example of the width Wobj is shown in the figure. As indicated by hatching in the figure, the CPU first specifies the outline in the perspective-projected map image of an object that is a character display target such as a building. It can also be said that a silhouette of an object (hereinafter sometimes referred to as “display area”) is obtained. Then, the maximum width of the closed figure or display area specified by this contour is measured and set as the horizontal width Wobj.
When the width of the character is the horizontal width Wobj (step S344), the CPU excludes the character from display (step S346). By doing so, it is possible to easily avoid displaying characters on a building or the like that is only partially visible in the perspective projection diagram, and to suppress the complication of the map.
If the width of the character is horizontal width Wobj ≦ (step S344), the character arrangement position is determined (step S348). As for the position in the left-right direction, it is preferable that the character frame is arranged with one end close to the end close to the vanishing point in the maximum width Wobj. By doing so, the protrusion from the object and the overlap with other buildings can be reduced.
Regarding the position in the vertical direction, first, the lowermost BL of the display area of the object is specified (step S350). As shown on the right side of the figure, the lowermost part BL does not mean the lowermost part of the object in three dimensions, but the lowest part in the vertical direction when the display area is viewed in a perspectively projected two-dimensional map image. It means lower part. Then, when the lowest BL is obtained, the CPU places the lowest point of the character here (step S352). As shown on the right side of the figure, by arranging the characters at the bottom BL, it is possible to avoid the characters from protruding greatly in the vertical direction from the object, and as a result, it is possible to suppress the characters from protruding vertically from the screen. is there.

  The character arrangement is not necessarily required by the method shown in FIG. For example, you may arrange | position so that the gravity center of a character frame may be matched with the gravity center position of a display area. In addition, it may be determined whether or not to display by determining the presence or absence of overlapping with other character frames and display areas of other objects. For example, as long as an area of a predetermined ratio or more in the area of the character frame to be displayed overlaps with other character frames and display areas, it may be excluded from the display target.

<< Intersection and destination display processing >>
12 and 13 are flowcharts of intersection and destination display. This process is a process of displaying the name of the intersection and the destination of the intersection exit, and is a process corresponding to step S370 of the character display process (FIG. 5). It is assumed that the character size of the intersection and the destination display is set in advance by the processing of FIGS.
The CPU first executes a process for displaying the name at the intersection. The CPU acquires a display area for the intersection (step S372). An example of the display area is shown on the right side of the figure.
A region ISC in the figure corresponds to a display region. When a map is drawn by the perspective projection method, some intersections are partially hidden by buildings BLD1, BLD2, and the like. The display area is an area excluding a portion hidden by a building from an intersection that should originally be defined only by a road polygon.
As shown in the figure, the display area ISC often has a complicated shape. Therefore, a rectangular area Ri having a constant width Wi inscribed in the display area ISC is obtained, and an intersection name is arranged at the center of gravity CG1 (not shown) (step S374).

  Then, the CPU sets other arrangement candidates for the intersection name. That is, based on the three-dimensional polygon data, the center of gravity position CGi of the intersection is obtained, and the intersection name is arranged at a point CG2 that is H above this point (step S376). The arrangement in the map image is determined by obtaining a point corresponding to the point CG2 by a perspective projection method.

The CPU selects one of the arrangement positions CG1 and CG2 thus obtained that has less overlap with the building name and displays the intersection name (step S378). Of course, the overlapping of the two arrangement positions CG1 and CG2 is not determined.
As for the building name, the positional relationship with the building is important and the degree of freedom of character arrangement is low, while the intersection name can be arranged in a plurality as described above. By selecting an arrangement on the side where there is little overlap with the name of a building or the like, it is possible to realize an easy-to-see display by making use of the degree of freedom of arrangement of the intersection name.
In the above-described example, the case where two arrangements are compared is shown, but more arrangement candidates may be considered. In addition, if any of the placement candidates overlaps with the building, one with a small area of the overlapping portion may be selected, or one of the candidate placements may be selected according to a preset priority. May be.
When the arrangement of the intersection name is determined, the CPU deletes the building name overlapping the intersection name (step S380). By doing so, the intersection name can be preferentially displayed. Various settings are possible for the priority of the intersection name and the building name, and the intersection name may be displayed only when it does not overlap with the building name. Moreover, the ratio of the part where the building name overlaps in the character frame of the intersection name may be obtained, and if this ratio is equal to or less than a predetermined value, the intersection name may be prioritized (the building name is deleted).

  When the intersection name is arranged, the CPU displays the destination of the intersection. For this process, first, the CPU acquires destination information for the target intersection (step S382).

A destination database that provides destination information will be described.
FIG. 14 is an explanatory diagram illustrating a destination database. In this embodiment, the destination database is stored as one of the character data 133, but may be stored in the road network data 131.
The structure of the destination database will be described taking the road shape shown in FIG. As shown in FIG. 14A, this intersection is composed of four links FL1 to FL4 connected to the node FN1. The link FL1 corresponds to “A street” as it goes to “□□”. The link FL2 corresponds to “B street” as it goes to “XX”. The link FL3 corresponds to “A street” as it goes to “**”. The link FL4 corresponds to “C street” as it goes to “ΔΔ”.
FIG. 14B shows an example of the destination database. A destination database is prepared for each node. In the example of the figure, a portion corresponding to the node FN1 illustrated in FIG. “Inter-link information” indicates a passing method of the node FN1 by a combination of an entrance link and an exit link. For example, “FL1 → FL2” represents a route that enters the node FN1 from the link FL1 and exits to the link FL2. “Destination” represents a character string of destination information to be displayed for the route, and “street name” represents a street name corresponding to the exit link in the route. For example, for the route “FL1 → FL2”, since the link FL2 corresponds to “B street” as it goes to “XX”, “XX” as “destination”, “ "B street" is stored. The same applies to other routes.
In this way, by using a database in which “destination” and “street name” are associated with the node passing methods, it is possible to perform highly convenient destination display according to the passing method.
For example, according to the data structure of FIG. 14 (b), in the interlink information “FL1 → FL3” and “FL2 → FL3”, even if the route has the link FL3 as an exit, as separate data, Different “destination” and “street name” can be stored. For the link information “FL1 → FL3”, since the links FL1 and FL3 are both links corresponding to “A street”, the “street name” data may be blanked to simplify the display. . In addition, when the destination information to be sought is different between the user heading from the link FL1 to the FL3 direction and the user heading from the link FL2 to the FL3 direction, an individual “destination” corresponding to this tendency may be stored. Good.
In the example of FIG. 14, “destination” and “street name” are stored, but only one of them may be stored.

  Referring to the destination database shown in FIG. 14, the CPU can acquire “destination” and “street name” for each exit as destination information for each intersection node. The destination information may be acquired regardless of the route search result. In the example of FIG. 14, when the link FL1 is traveling toward the node FN1, the inter-link information “FL1 → FL2” and “FL1 → FL3” including the link FL1 as the approach link regardless of the route search result. All data “FL1 → FL4” may be acquired.

Returning to FIG. 13, the contents of the intersection / destination display process will be described.
When the destination information is acquired, the CPU displays the destination information. As for the destination information, as with the intersection name, a plurality of candidate display positions are set and any one is selected. As a first candidate, the CPU arranges a destination display at the midpoint D1 of the intersection line between the exit road polygon and the intersection (step S384). As a second candidate, a destination display is arranged at a point D2 above Hm above the boundary between the exit road link and the intersection (step S386). Then, one of D1 and D2 that does not overlap with the building name is selected and displayed as a destination (step S388). In the case of an intersection name, the intersection name is preferentially displayed over the building name (steps S378 and S380). However, since the destination display is considered to be less important than the intersection name, the building name is given priority. . The destination name may also be displayed with priority over the building name, similar to the intersection name.

An example of setting the above-described two candidate display positions will be specifically described.
FIG. 15 is an explanatory diagram of a destination display example. FIG. 15A shows an example of setting candidate display positions. In order to avoid complication of the figure, the candidate position D1 is shown on the link FLR on the right side of the figure, and the candidate position D2 is shown on the link FLL on the left side. The area ISC2 with the central hatching is the intersection area.
The candidate position D1 is set at the midpoint of the intersection line between the road polygon corresponding to the right link FLR and the intersection area ISC2. You may make it set to the intersection of link FLR and an intersection area | region. Actually, a candidate position corresponding to the point D1 is obtained for the left link FLL.
On the other hand, as the candidate position D2, a perpendicular line with the intersection DH between the link FLL and the intersection area ISC2 as a foot is obtained and displayed at the point D2 at a position having a height Hm from the intersection DH. Specifically, the point D2 in the three-dimensional space is obtained, and the display position on the map drawn by the perspective projection is specified. Actually, a candidate position corresponding to the point D2 is also obtained for the right link FLR.
Then, when the destination display is performed at the two candidate positions obtained for each link FLR, FLL, the one that does not overlap with the building name is selected.

FIG. 15B shows a display example of destination information. The horizontal names of “Gion” and “Shiobara” surrounded by broken lines are the destination display of “Minoshima intersection”. The name of the vertical name “Hundenenbashi Street” in the center is the street name display. Here, an example is shown in which a destination and a street name are displayed separately. The display character size can be set in the same way as the intersection name. The use of vertical writing / horizontal writing can be set as vertical writing if the corresponding link is inclined at 45 to 90 degrees (a state close to vertical) in the map image, and horizontal writing in other cases. Either vertical writing or horizontal writing may be standardized, street names may be written vertically, and destinations may be written horizontally, depending on the content.
If the destination display is performed for all the intersections, the screen becomes complicated. Therefore, the destination display may be performed only for the intersection in the foreground.

  In this embodiment, as shown in FIG. 14B, two types of destination information, “destination” and “street name” are prepared. These two ways can be properly used in various ways. For example, the user may instruct which to display. In addition, “street name” may be used for streets close to the front, and “destination” may be used for streets turning left and right, depending on the direction. For example, if the angle between the entrance link and the exit link is equal to or less than a predetermined value (a state that is almost straight), a “street name” can be used, and a “destination” can be used in other cases. .

<< Effects and Modifications >>
According to the three-dimensional map display system of the embodiment described above, the character itself can have a sense of perspective by changing the character size according to the depth. As a result, it is easy to intuitively understand the correspondence between characters and buildings.
In addition, by setting the display ratio of the character size according to the depth to be different from the display ratio applied to buildings, etc. in the perspective projection method, it is possible to avoid the character size from becoming too small or too large and readable. It is possible to avoid complication of the image while displaying.

The present invention can be realized in various modes. The various processes described above do not necessarily have to include all of them, and some of them can be omitted or replaced with other processes.
In the above-described example, the process executed in software may be executed in hardware and vice versa.

  The present invention can be used to display characters on a three-dimensional map that represents a feature three-dimensionally.

DESCRIPTION OF SYMBOLS 100 ... Three-dimensional map display system 101 ... Display 102 ... Switch 110 ... Main control part 111 ... GPS
DESCRIPTION OF SYMBOLS 112 ... Route search engine 113 ... Route search result 114 ... Route guidance part 115 ... Command input part 120 ... Display control part 121 ... Background drawing part 122 ... Character display part 123 ... Route display part 130 ... Map database 131 ... Road network data 132 ... 3D polygon data 133 ... Character data

Claims (10)

A three-dimensional map display system for drawing a three-dimensional map representing three-dimensional features,
Three-dimensional polygon data for generating the background image of the three-dimensional map by rendering the feature three-dimensionally by perspective projection, and a character string and display for displaying a predetermined name in the background image A map database for storing character data for specifying the position;
A background drawing unit that generates the background image by three-dimensionally drawing a feature by perspective projection using the three-dimensional polygon data;
A character display unit that displays characters representing the predetermined name in the background image using the character data;
The character display section
For the character string of each name, the character of the character string is reduced so that the character frame including the character string becomes smaller at a display ratio different from the display ratio in the perspective projection method according to the depth from the viewpoint in the perspective projection method. A three-dimensional map display system for displaying the character by changing at least one of size and character spacing. The three-dimensional map display system according to claim 1,
The character display unit is a three-dimensional map display system that changes the size of the character frame at a display ratio more gradual than the perspective projection method when the depth is within a predetermined value or less. The three-dimensional map display system according to claim 1 or 2,
The character display unit is a three-dimensional map display system that displays a character positioned within a predetermined depth range from the viewpoint position. It is a three-dimensional map display system in any one of Claims 1-3,
The three-dimensional map display system, wherein the character display unit changes at least one of the character size and character spacing within a preset limit value range. A three-dimensional map display system according to any one of claims 1 to 4,
The character display unit is a three-dimensional map display system that applies different display ratios between a vertically long character frame and a horizontally long character frame. A three-dimensional map display system according to any one of claims 1 to 5,
The character display section
In the outline of the feature and background to be the display target of the character as the display region of the character,
A three-dimensional map display system for displaying a character when the maximum width of the display area is larger than the width of the character frame. A three-dimensional map display system according to any one of claims 1 to 5,
The character display section
The display position of the character in the map is set by a plurality of methods,
A three-dimensional map display system that selects a display position where there is little overlap between character frames of the character and other characters among the set display positions. A three-dimensional map display system according to any one of claims 1 to 7,
The map database has a destination database that stores destinations in the exit directions of the intersections in association with the approach directions to the intersections for the intersections in the map,
The said character display part specifies the said approach direction based on the gaze vector in the said perspective projection method, The three-dimensional map display system which displays the character showing the said destination using the said destination database. A three-dimensional map display method for drawing a three-dimensional map representing three-dimensional features by a computer having a map database,
The map database
Three-dimensional polygon data for generating the background image of the three-dimensional map by rendering the feature three-dimensionally by perspective projection, and a character string and display for displaying a predetermined name in the background image It is a database that stores character data specifying the position,
The computer
A background drawing step of generating the background image by three-dimensionally drawing a feature by perspective projection using the three-dimensional polygon data;
Performing a character display step of displaying a character representing the predetermined name in the background image using the character data;
In the character display step,
For the character string of each name, the character of the character string is reduced so that the character frame including the character string becomes smaller at a display ratio different from the display ratio in the perspective projection method according to the depth from the viewpoint in the perspective projection method. A three-dimensional map display method for displaying characters by changing at least one of size and character spacing. A computer program for drawing a three-dimensional map representing a three-dimensional feature by a computer having a map database,
The map database
Three-dimensional polygon data for generating the background image of the three-dimensional map by rendering the feature three-dimensionally by perspective projection, and a character string and display for displaying a predetermined name in the background image It is a database that stores character data specifying the position,
The program is
A background drawing function for generating the background image by three-dimensionally drawing a feature by perspective projection using the three-dimensional polygon data;
A program for executing a character display function for displaying a character representing the predetermined name in the background image using the character data;
The character display function is
For the character string of each name, the character of the character string is reduced so that the character frame including the character string becomes smaller at a display ratio different from the display ratio in the perspective projection method according to the depth from the viewpoint in the perspective projection method. A computer program having a function of displaying the character by changing at least one of size and character spacing.

Images