JP3954178B2 - 3D map display device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a three-dimensional map display device that displays a map on a three-dimensional topographic map on a display or the like.
[0002]
[Prior art]
Conventionally, in a map display device, digital map data stored in a storage medium such as a CD-ROM or DVD-ROM is read, and a structure, a road, a place name, etc. are coordinate-transformed and drawn as an arbitrary scale plan view. A map was displayed on the display device. Further, as described in Japanese Patent Laid-Open No. 8-292720, a planar map is viewed from a viewpoint position of an arbitrary height, and an overhead view projected on a projection plane provided between the planar map and the viewpoint is displayed. There is also a pseudo 3D display. A feature of the pseudo three-dimensional display is that detailed map information in the vicinity of the viewpoint and outline information in the distance from the viewpoint can be grasped on the same screen. Furthermore, there is also a method for expressing the difference in topography by drawing contour lines and colors corresponding to the contours on these two-dimensional maps and maps displayed in a pseudo three-dimensional manner.
[0003]
In the pseudo three-dimensional map display, the coordinates are converted and rendered based on the two-dimensional map data on the assumption that all the planes have the same height. Therefore, it has been difficult to express a three-dimensional shape such as undulations of mountains and valleys. Furthermore, even in a method of drawing contour lines and colors according to contours on a planar map or a pseudo 3D map, the displayed map screen is far from the actual topography, and it is difficult to display a more realistic overhead view. Met.
[0004]
As a method for solving this problem, a vertex coordinate in which elevation data is recorded is read, a three-dimensional model is created with a topographic mesh formed by connecting the vertices as a minimum unit, and the two-dimensional map data is created there. There is a three-dimensional map display that obtains a three-dimensional terrain display by overlaying. In 3D map display, the viewpoint position is set so as to include a point to be overlooked, and the terrain shape constituted by the 3D model and the map overlapping it are projected onto a projection screen, that is, a display screen such as a display. To do.
[0005]
[Problems to be solved by the invention]
In the 3D map display, the 3D terrain shape is looked down on from the set viewpoint position. Therefore, particularly in mountainous areas, a slope of the mountain opposite to the viewpoint position, a topographic surface hidden by a mountain in front or the like, that is, a hidden surface is generated, and it is essential to delete the hidden surface.
[0006]
The hidden surface removal method has depth information for each pixel of the display screen, determines the depth information at the time of drawing for each pixel, and draws if it is on the near side, Z buffer method, terrain constituting a three-dimensional topographic map Sorts meshes and map data in depth order, draws in order from the viewpoint farther toward the front, and selects and draws the terrain mesh and map data constituting the 3D topographic map in order from the viewpoint farther toward the front. There are methods such as a painter algorithm.
[0007]
Here, the Z buffer requires a rendering processor having a comparator for executing depth determination for each pixel, or rendering software for rendering each pixel while determining the depth. Therefore, the hidden surface removal in the three-dimensional map display affects the drawing in units of pixels, and it is difficult to realize it using a drawing processor that draws a generally used two-dimensional plane. Therefore, the focus is on the case of using a Z sort method or a painter algorithm that can be realized in a drawing processor for drawing a two-dimensional plane for hidden surface removal. When a 3D map is displayed using the Z sort method and painter algorithm, the following problems occur in hidden surface removal.
[0008]
A first problem is that road data included in map data and background data representing a water system and a green zone are generated independently of altitude data. Therefore, there is no guarantee that there are vertices where the polygonal lines and faces constituting the map data intersect with the terrain mesh. For this reason, when the terrain mesh and map data are sorted or selected in order from the far field of view and drawn, a cyclical overlap occurs and there is a problem that hidden surface removal cannot be performed completely.
[0009]
The second problem is the large processing load of sorting the terrain data and map data implemented in the Z sort method, or the terrain data and map data implemented in the painter algorithm in order from the back, completing the 3D map display. There is a problem of increasing the time to do so. Furthermore, if the size of the terrain mesh is fixed, there is a problem that the number of terrain meshes that must be drawn increases when the viewpoint height is increased, and the processing load increases.
[0012]
[Means for Solving the Problems]
In order to solve the above problems, the following means are used.
[0013]
As means for solving the first problem, means for dividing the map data in units of terrain mesh is used. On the other hand, the means for dividing the map data into terrain mesh units can perform complete hidden surface removal, but the processing load is heavy. Therefore, a means for determining whether or not a hidden surface exists in the three-dimensional map to be displayed is divided into map data in units of terrain mesh when it is determined that there is a hidden surface, and map in units of terrain mesh when it is determined that there is no hidden surface. Operates to skip data partitioning.
[0014]
As means for solving the second problem, means for storing a drawing instruction and a branch instruction for drawing map data divided for each terrain mesh as a set is used. Furthermore, in the case of a viewpoint height or depression angle over which a wide area can be seen, means for changing the size of the terrain mesh is used.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment in which a three-dimensional map display device is applied to a navigation device will be described below with reference to the drawings.
[0018]
FIG. 1 shows a display example of the three-dimensional map display of the present invention. Map data such as terrain, roads, character strings, etc. is divided into terrain mesh 2001 units constituting the terrain plane, and the terrain mesh and the divided map data are drawn in order from the viewpoint far away to the vicinity of the viewpoint to draw a three-dimensional map. Displayed on the output device 2.
[0019]
FIG. 2 shows the configuration of the navigation device. Hereinafter, details of each component unit of the navigation device will be described.
[0020]
The arithmetic processing unit 1 detects a current position based on sensor information S5 to S8 output from various sensors 5 to 8, reads map data necessary for map display from the obtained current position information from the storage means 3, The user develops the map data in graphics and displays the map on the output device 2, selects the optimum route connecting the destination and the current location instructed by the user, and displays the map superimposed on the map on the output device 2. It is a central unit that performs various processes such as guiding the car to the destination.
[0021]
The output device 2 is a unit that displays graphics information generated by the arithmetic processing unit 1, and is configured by a CRT or a liquid crystal display. The signal S1 between the arithmetic processing unit 1 and the output device 2 is generally connected by an RGB signal or an NTSC (National Television System Committee) signal.
[0022]
The storage means 3 is composed of a large-capacity storage medium such as a CD-ROM, a DVD-ROM, or an IC card, and stores map data, altitude data, and the like necessary for map display.
[0023]
The input device 4 is a unit that receives an instruction from a user, and includes a hardware switch such as a scroll key and a scale change key, a joystick, a touch panel pasted on a display, and the like.
[0024]
The sensor used to detect the position in the navigation device measures the distance from the product of the wheel circumference and the measured wheel rotation speed, and the moving body bends due to the difference in the rotation speed of the paired wheels. Wheel speed sensor 5 that measures the angle, geomagnetic sensor 6 that detects the magnetic field held by the earth and detects the direction in which the moving body is facing, and a gyro that detects the rotation angle of the moving body such as an optical fiber gyroscope and a vibrating gyroscope 7. Measure the current position, traveling speed, and traveling direction of the moving object by receiving the signals from the GPS satellite and measuring the distance between the moving object and the GPS satellite and the rate of change of the distance for three or more satellites. The GPS receiver 8 is used. Further, the GPS receiver 8 can obtain time information and date information by analyzing signals from GPS satellites.
[0025]
In addition, an in-vehicle LAN device 9 is provided for receiving various information on the vehicle, such as door opening / closing information, the type and status of lights that are lit, the status of the engine and the result of failure diagnosis.
[0026]
FIG. 3 is a diagram illustrating the hardware configuration of the arithmetic processing unit 1.
[0027]
Hereinafter, each component will be described. The arithmetic processing unit 1 is configured by connecting the devices 21 to 31 in the figure with a bus. Each component includes a CPU 21 that executes various processes such as numerical calculations and control of each device, a RAM 22 that stores maps and search data, a calculation data, a ROM 23 that stores processing programs and data, a high-speed memory and a memory, DMA (Direct Memory Access) 24 for executing data transfer between the memory and each device, drawing commands and branch commands stored in the unified memory 26 are received and the pixel information is rapidly developed in the frame memory space in the unified memory. A graphics processor 25 for executing graphics rendering and display control, a unified memory 26 for storing rendering results and rendering commands, a color palette 27 for converting image data composed of palette IDs of respective colors into RGB luminance information signals, A / D converter 28 for converting an analog signal into a digital signal, Converting one signal to a parallel signal synchronized with the bus SCI29, composed of counter 31 for integrating PIO30 placed on the bus takes a parallel signal synchronized, the pulse signal. FIG. 4 is a diagram illustrating the functional configuration of the arithmetic processing unit 1. Details of each component will be described below.
[0028]
The current position calculation means 42 uses distance data and angle data obtained as a result of integrating the distance pulse data S5 measured by the wheel speed sensor 5 and the angular acceleration data S7 measured by the gyro 7, respectively. By integrating with the shaft, a process of calculating the position (X ′, Y ′) after traveling the moving body from the initial position (X, Y) is performed. Here, in order to match the relationship between the rotation angle of the moving body and the traveling direction, the angle data obtained by integrating the direction data S6 obtained from the geomagnetic sensor 6 and the angular acceleration data S7 obtained from the gyro 7 are in a one-to-one relationship. And the absolute azimuth in the direction in which the moving object is traveling is corrected. Further, when the data obtained from the above-described sensor is integrated, the sensor error accumulates, so that the accumulated error is canceled based on the position data S8 obtained from the GPS receiver 8 at a certain time period. To output the current position information.
[0029]
Since the current position information includes sensor errors, the map matching means 43 is performed for the purpose of further improving the position accuracy. This is because the road data included in the map around the current location is read from the storage means 3 by the map data reading means 44, the travel locus shape obtained from the current position calculating means 42 and the road shape are compared with each other, and the correlation between the shapes is the most. This is a process of adjusting the current location to a high road. By applying the map matching process, the current location often coincides with the traveling road, and the current position information can be output with high accuracy.
[0030]
The user operation analysis means 41 receives a request from the user by the input device 4, analyzes the request content, and controls each unit so as to execute a corresponding process.
[0031]
The map display means 45 uses the map data and elevation data read by the map data reading means 44 from the storage means 3 and transfers drawing data for drawing a three-dimensional map looking down on the terrain at a predetermined depression angle and a predetermined scale from the viewpoint position. To work. The viewpoint position may be set to a position that is a predetermined distance away from the current position on the map or the point to be displayed in the direction opposite to the line of sight.
[0032]
The menu display means 46 operates to draw buttons and menu lists that serve as user interfaces, and to transfer the drawing data to the display processing means 47.
[0033]
Based on the drawing data from the map display means 45 and the menu display means 46 described above, the display processing means 47 converts pixels, lines, planes, images, and characters representing the map and the menu screen into the frame memory in the unified memory 26. expand.
[0034]
Details of the map display means 45 for generating drawing data for displaying a three-dimensional map will be described below.
[0035]
FIG. 5 is a diagram for explaining the functional configuration of the map display means 45.
[0036]
The map data request means 50 is composed of map data included in the area to be displayed on the map, that is, road data composed of road attributes and shapes thereof, polygon attributes representing buildings, green zones, rivers, etc. and shapes thereof. The background data, the character / symbol data composed of the character / symbol code such as the place name and the facility name and the coordinate data of the point where they are located, and the region to be displayed on the map are divided at predetermined intervals in the x-axis and y-axis directions. The altitude data composed of the altitude values of the vertices are read from the storage means 3.
[0037]
The terrain mesh calculation means 51 calculates the visible area of the map displayed on the display screen from the viewpoint position and the depression angle, and generates a rectangular terrain mesh that expresses the terrain surface from the altitude data existing in the visible area.
[0038]
The coordinate conversion means 52 converts the map data and elevation data read by the map data request means 50 so that the line-of-sight direction coincides with the y-axis and the viewpoint position is the origin.
[0039]
The hidden surface presence / absence determining unit 53 performs projection conversion of the terrain mesh generated by the terrain mesh calculating unit 51 by the projection conversion unit 57, and determines whether or not there is a terrain mesh to be hidden from the result of the projection conversion. If there is a hidden terrain mesh, the process moves to the map data dividing means 54, and if not, the process moves to the map data storage means 56.
[0040]
The map data dividing means 54 divides road data and background data included in the map data for each terrain mesh.
[0041]
The character string processing means 55 corrects the timing for drawing a character string such as a name and a symbol and the drawing position on the display screen.
[0042]
The map data storage means 56 divides the map data when the hidden surface presence determining means 53 determines that a hidden surface exists, and the map data read when the hidden surface presence determining means 53 determines that there is no hidden surface. Projection conversion is performed, and a drawing instruction and a branch instruction are stored as a pair.
[0043]
The projection conversion unit 57 includes vector data and point data constituting the map data on a projection plane (display screen) existing at a specified depression angle from the viewpoint position 1005 shown in FIG. Projects and converts the vertex coordinates that make up the terrain mesh.
[0044]
The drawing means 58 selects and draws a terrain mesh at an arbitrary position and map data to be drawn over the terrain mesh. By performing these processes in the order from the far viewpoint to the vicinity of the viewpoint, the hidden surface removal of the topographic map and the map is realized.
[0045]
Next, details of the coordinate conversion means 52 will be described with reference to FIG.
[0046]
The coordinate conversion means 52 uses the map data and altitude data read by the map data request means 50 as the map data and the viewpoint position 1005 shown in FIG. 6 is the origin (0, 0) and the line-of-sight direction 1006 coincides with the y coordinate axis. And coordinate conversion so that the scale of the altitude data matches. Here, the viewpoint position may be set at a point away from the own vehicle position by a predetermined distance in the direction opposite to the line of sight, and higher than the own vehicle position by a predetermined height. Further, the line-of-sight direction may be set to the traveling direction of the host vehicle. Accordingly, the terrain mesh 2001 and the map data are in the same coordinate system, and the rectangles constituting each terrain mesh are parallel to the x-axis and the y-axis. 54 can be simplified.
[0047]
Next, details of the terrain mesh calculation means 51 will be described with reference to FIGS.
[0048]
The visible region calculation means 70 is a coordinate system in which the viewpoint position 1005 shown in FIG. 7 is the origin, and the line-of-sight direction 1006 is the top (y-axis). Assuming that the altitudes of all the points are the same, the range (visible region) 1004 of the two-dimensional map projected on the display screen is calculated when looking down from the viewpoint position in the line-of-sight direction.
[0049]
Next, in the terrain mesh size calculation 71, the size of the terrain mesh constituting the terrain plane is determined. In the device that displays a three-dimensional map viewed from an arbitrary viewpoint height, the visible region 1004 becomes wider when the viewpoint position becomes higher. As a result, if the terrain mesh sizes dx and dy are fixed, the number of terrain meshes increases in the square order, and the processing load increases. Therefore, processing for determining the terrain mesh sizes dx and dy based on the viewpoint height and the depression angle is used. For example, the mesh size may be determined by multiplying the reference terrain mesh sizes dx and dy by the ratio between the reference viewpoint height and the set viewpoint height. Furthermore, the terrain mesh sizes dx and dy corresponding to each viewpoint height may be provided as a table, and the terrain mesh sizes dx and dy corresponding to the arbitrary viewpoint height may be determined from this table. Although the example using the viewpoint height as a parameter has been described here, the size of the terrain mesh can also be determined by performing the same processing using the depression angle as a parameter. Further, the size of the terrain mesh may be determined from the relationship between the viewpoint height and the depression angle. Thus, the number of terrain meshes to be drawn is controlled so as not to increase significantly, and the processing load when the visible region is enlarged can be reduced.
[0050]
The terrain mesh generation 72 divides the visible region 1004 for each terrain mesh size dx, dy obtained by the terrain mesh size calculation 71, and calculates the coordinate value of each vertex 2002 constituting the terrain mesh 2001. In this embodiment, the terrain mesh shape is rectangular, but the terrain mesh shape may be triangular.
[0051]
The minimum elevation extraction 73 is performed in order to prevent a terrain polygon dropout that occurs when looking down at a terrain area where the elevation of the viewpoint position 1005 is high and the elevation is low, and among the elevation values included in the visible area 1004 in the elevation data. Extract the lowest elevation value.
[0052]
Next, the visible region correction 74 calculates the difference between the elevation value of the viewpoint position and the elevation value extracted by the minimum elevation extraction 73, and uses the difference value as a parameter in the horizontal direction perpendicular to the line-of-sight direction as shown in FIG. A right additional terrain mesh 2003 and a left additional terrain mesh 2004 are added. There is a method of setting the number of meshes to be added for each predetermined height of the difference value as a calculation method of the terrain mesh to be added. This is, for example, a method in which a terrain mesh is added one by one to the left and right with a difference value of 100 m. Note that processing may be performed using the current position altitude instead of the viewpoint position altitude.
[0053]
Each vertex 2002 of the terrain mesh generated by the above processing is a vertex on a two-dimensional plane, and it is necessary to obtain an elevation value at each vertex in order to perform three-dimensional map display. Therefore, in the altitude value calculation 75, the altitude value of the vertex constituting the topographic mesh is calculated from the altitude data read out by the map data request means 50. Here, the vertex coordinates recorded in the elevation data do not match the vertex coordinates constituting the terrain mesh. Therefore, for example, as shown in FIG. 6, vertices 2040, 2041, surrounding the vertex 2002 are displayed.
The elevation data 2042 and 2043 are read, and the elevation value of the vertex 2002 is calculated. Here, the coordinates of the altitude 2040 are (x1, y1, z1), the coordinates of the altitude 2041 are (x2, y1, z2), the coordinates of the altitude 2042 are (x2, y2, z3), and the coordinates of the altitude 2043 are (x1, If y2, z4), the elevation value zp with respect to the coordinates of the vertex 2002 as (xp, yp) is obtained by calculating Equation 1, Equation 2, and Equation 3.
[0054]
[Expression 1]
Za = (yp−y1) × (Z4−Z1) / (y2−y1) + Z1 (Expression 1)
[0055]
[Expression 2]
Zb = (yp−y2) × (Z3−Z2) / (y2−y1) + Z2 (Expression 2)
[0056]
[Equation 3]
Zp = (xp−x1) × (Zb−Za) / (x2−x1) + Za (Equation 3)
Next, details of the hidden surface presence determination means 53 will be described with reference to FIG.
[0057]
If there is no hidden terrain on the map to be displayed, the process of dividing the map data into terrain mesh units is omitted, and after all the terrain surfaces are drawn, the map data can be overlaid on the terrain and drawn in 3D. The phenomenon that the map is hidden by the hidden surface or the hidden surface is displayed does not occur. Further, in the three-dimensional map display, a terrain mesh that is a hidden surface is generated in a mountainous area, but the probability that a terrain mesh that is a hidden surface is generated in a plain part is extremely low. Furthermore, regions with a large amount of map data, such as large cities, have the characteristic of being concentrated in plains.
[0058]
Therefore, in the hidden surface presence / absence determining means 53, the projection conversion means 57 projects and converts all the vertices constituting the terrain mesh in the visible region, and y on the projection plane of a vertex 2010 and a vertex 2011 adjacent to the far side of the viewpoint. Compare the magnitude relation of the axis (upward projection plane) coordinates. As shown in the hidden surface mesh example b) in FIG. 9, if the y coordinate of the vertex 2011 on the farther viewpoint than the vertex 2010 is small on the projection surface, the terrain mesh including the two vertices is determined to be a hidden surface. To do. Based on the determination result, the process transitions to the map data dividing means 54 if there is even one hidden terrain mesh, and to the map data storage means 56 if not.
[0059]
Thereby, since map data is divided | segmented into a terrain mesh unit only when the terrain mesh used as a hidden surface exists, the processing load required for the map data division | segmentation process in a plain part can be reduced.
[0060]
Next, details of the map data dividing means 54 will be described with reference to FIG.
[0061]
The map data acquisition means 80 acquires the vertex data which comprises the continuous line and surface data with the same attribute according to a map format. Terrain mesh position calculation means
In 81, the maximum value and the minimum value of the y coordinate (line-of-sight direction) of the acquired vertex data are extracted, and the column position (terrain mesh position in the y-axis direction) including these two y coordinates is calculated. This processing can be easily obtained by dividing the y-coordinate by the terrain mesh size because the terrain mesh and map data have already been converted into a coordinate system in which the viewing direction is the y-axis direction.
[0062]
The column determination unit 82 determines whether the column position for the maximum value of the vertex data and the column position for the minimum value are the same column position. If the two column positions are the same, the vertex data does not span multiple column areas, so there is no need to divide the area. However, if the two column positions are different, the data for each column in which the vertex data exists is stored. It is necessary to divide. Therefore, the interpolation point generation means 83 calculates the intersection between the vertex data and the boundary of each column to generate an interpolation point. For example, in the case of a broken line 3001, the maximum value of the y coordinate is included in column 4 and the minimum value is included in column 2. Therefore, the broken line 3001 is divided for each vertex data included in the column 2, the column 3, and the column 4. Therefore, the vertex data A, B, and C are divided by calculating the intersection of each column boundary and the broken line 3001. In the case of surface data 3003, the maximum value of the y coordinate is included in column 3 and the minimum value is included in column 1. Therefore, the plane data 3003 is divided for each area included in the column 1, the column 2, and the column 3. Therefore, the intersection of each column boundary and the surface data 3003 is calculated, and the three surface data E, F, and G are divided into vertex data constituting each. In this way, all map data is converted into vertex data divided for each column. Therefore, since the management area of the terrain mesh and the terrain data is the same, a cyclic overlap does not occur and a high-quality three-dimensional map can be displayed.
[0063]
Next, the character string processing means 55 will be described with reference to FIGS.
[0064]
FIG. 11 shows a display example of a character string. In order to faithfully represent the position of the character string or symbol in the actual terrain, when a part of the character string or symbol is hidden by the near object, only the overlapping portion with the object is hidden. For this reason, hidden surface removal of a character string is also performed in the same manner as vector data such as roads. However, unlike vector data, the character string display occupies a rectangular area, and the terrain mesh where the character string exists does not match the rectangular area of the character string. In order to prevent such a character string from being unduly erased due to the overlap, the character string processing unit 55 changes the drawing timing of the character string and the symbol and corrects the drawing position of the character string and the symbol on the display screen.
[0065]
The detailed processing of the character string processing means 55 will be described below with reference to FIG.
[0066]
The character string data acquisition 91 reads the drawing coordinate position, the number of characters and the character code of the character string recorded in the map data, or the drawing coordinate position of the symbol, the symbol code and the symbol image. Further, the altitude value at the drawing coordinate position is calculated from the altitude data.
[0067]
The overlap determination 92 projects and converts the drawing position coordinates of all character strings and symbols, and calculates the position and size of the rectangular area occupied on the character string display screen from the number of characters and the character code. Next, all character strings and symbols are regarded as objects to be displayed, and are sorted in order from the shortest distance from the viewpoint position. Further, display priority is given to character strings and symbols in the vicinity of the viewpoint position, and character strings and symbols that overlap the display priority character strings and symbol rectangular areas are deleted from the character strings and symbols to be displayed. Thereby, the overlapping of character strings and symbols on the display screen is reduced, and visibility is improved.
[0068]
The character string position determination 93 extracts the y-coordinate (line-of-sight direction) of the drawing position coordinates of the character string and symbol that are displayed by the overlap determination 92, and the column position (the terrain mesh in the y-axis direction) that includes the y-coordinate. Position).
[0069]
The character string position correction 94 obtains a column position adjacent to the vicinity of the viewpoint position from the column position for each character string or symbol obtained in the character string position determination 93. Using this column position information, the timing for drawing a character string and a symbol is determined. For example, in FIG. 11, the character string 4001 is included in the column 3, but is corrected to the character string included in the column 2 (note that the drawing position is not corrected). Thus, after the terrain mesh in the column 2 is drawn, the map data included in the column 2 is drawn, and at the same time, the character string 4001 is drawn. As a result, the possibility that the character string or the symbol is hidden by the topographical mesh on the near side of the viewpoint is reduced, and the hidden surface removal is normally performed.
[0070]
The character string drawing position correction 95 calculates a drawing offset 4012 on the display screen based on the column position including the character string and the symbol, and shifts the character string and the symbol upward in the display screen by the obtained drawing offset. Then draw. This is executed in order to solve the problem that the height of the terrain mesh is smaller than the height of the character string or symbol in the terrain mesh far from the field of view, and the hidden surface is not completely erased even if the character string position correction 94 is used. The As a drawing offset amount calculation method, for example, the number of columns from the column closest to the viewpoint position to the column including the drawing position coordinates of character strings and symbols may be counted, and this number of columns may be used as the drawing offset 4012. Here, if the height of the character string or symbol is a specified value, the specified value is added to the character drawing position as the drawing offset 4012 if the drawing offset 4012 is smaller than the specified value, and the specified value if the drawing offset 4012 is larger than the specified value. May be added as a drawing offset 4012 to the drawing position of a character or symbol. By performing such processing, it is possible to minimize the possibility that part or all of the character string and symbols are hidden by the terrain mesh in front of the viewpoint. As a result, it is possible to prevent the character strings and symbols from being unduly hidden in the terrain mesh, and to improve the display quality of the character strings and symbols.
[0071]
Next, the details of the map data storage means 56 for storing the map data divided for each column will be described. When the hidden surface presence / absence determining unit 53 determines that there is no hidden surface, the processing is performed assuming that all data exists in the same column.
[0072]
An example of a format for storing map data in the memory in the map data storage means 56 is shown in FIG. In this embodiment, a map data storage memory 101 for storing a drawing instruction and a branch instruction composed of a vertex coordinate sequence and the number of vertices obtained as a result of projecting the map data divided for each column in pairs, The management table 100 is configured to manage the storage position of the drawing data for the column by the start address and the end address.
[0073]
Details of the map data storage means 56 will be described with reference to FIG.
[0074]
The initialization 110 initializes the start address and end address of the management table 100 to predetermined addresses. For example, the initial value set here may be a NULL value or the like.
[0075]
The divided map data acquisition 111 acquires vector data divided for each terrain mesh or column, column positions, and elevation values corresponding to each vertex of the vertex data.
[0076]
The stored data determination 112 refers to the management table 100 in the column from the column position of the map data acquired in the divided map data acquisition 111, and determines whether the start address is an initial value. When the start address is an initial value, the process branches to the start address setting 113, and when an address other than the initial value is set as the start address, the process branches to the branch address correction 114.
[0077]
The start address setting 113 sets an address at which a drawing command to be stored in the map data storage memory 101 is stored as a storage start address of the management table 100. For example, when the drawing command 1 (6001) is stored in the address 1 of the map data storage memory 101, the address 1 is stored in the start address of the column 4 to be drawn in this drawing command.
[0078]
Based on the last address stored in the management table 100, the branch address correction 114 changes the address of the branch instruction previously combined with the drawing instruction stored in the same column to the storage start address of the drawing instruction to be stored. To do. For example, when the drawing command 4 (6007) is to be stored at the address 7 of the map data storage memory, the final address of the column 4 to be drawn by this drawing command, that is, the address 2 is read from the management table 100 and stored in the drawing data storage memory. Address 7 is stored in the address of branch instruction 1 (6002) at address 2.
[0079]
The projection conversion 115 calls the projection conversion means 57 to perform projection conversion of the given vector data and convert it into a vertex coordinate sequence on the display screen.
[0080]
The instruction buffer write 116 sequentially stores a drawing instruction and a branch instruction composed of a vertex coordinate sequence obtained by projecting the vertex data and the number of vertices and the branch instruction in the map data storage memory 101 next to the stored final branch instruction. . For example, when branch instruction 3 (6006) has already been stored and drawing instruction 4 (6007) is to be stored, drawing instruction 4 (6007) is stored at address 7 and branch instruction (6008) is stored at address 8.
[0081]
The end address setting 117 updates the end address of the column position management table 100 corresponding to the drawing command written by the command buffer write 116 to the address storing the branch command stored in the map data storage memory 101. For example, when the drawing command 4 (6007) is stored, the final address corresponding to the column 4 in the management table 100 is corrected to the address 8 (in FIG. 13, the value before this correction is shown).
[0082]
In the end determination 118, it is determined whether or not all map data has been stored, and the above processing except for the initialization 110 is repeated until all data storage ends.
[0083]
By using such a storage method, map data corresponding to an arbitrary column can be easily referred to from the viewpoint back to the front, and map data corresponding to the arbitrary column can be selected at high speed. In addition, if the navigation apparatus has a drawing processor that can draw a line, a surface, etc. by interpreting a drawing command, the drawing command and the branch command are constituted by the drawing command, thereby drawing the map data storage memory 101 and the drawing command. The command storage buffer can be used as one memory area, and the memory area to be used can be reduced.
[0084]
Next, details of the drawing means 58 will be described with reference to FIGS.
[0085]
The hidden surface processing drawing 130 first selects a column located farthest from the viewpoint, and calls the projection conversion means 57 to draw and convert the terrain mesh corresponding to the selected column to draw. Next, with reference to the management table 100, the start address corresponding to the selected column is read, and the selected column is drawn, so that the map is displayed overlaid on the terrain mesh. Furthermore, a character string and a symbol corresponding to the selected column are selected and drawn so that the character string and the symbol are displayed so as to be superimposed on the terrain mesh and the map. These processes are repeated in the order from the column far from the viewpoint to the column near the viewpoint. This realizes hidden surface removal.
[0086]
In addition, when the elevation value of the terrain mesh located near the viewpoint position is high due to terrain undulation, there is a problem that a terrain polygon dropout 5000 occurs at the bottom of the screen as shown in FIG. In order to solve this problem, the display terrain determination 131 selects a vertex group constituting the nearest terrain mesh row 5001 in the visible region 1004 shown in FIG. 15, and further extracts the nearest vertex row 5002 close to the viewpoint. Projection conversion is performed, and it is determined whether or not the nearest vertex column 5002 subjected to the projection conversion exists above the lower boundary 5003 of the display screen. If it is determined that the nearest vertex column 5002 is present above the lower boundary 5003 of the display screen, the process branches to the display landform correction 132, and if it is determined not to exist, the process is terminated.
[0087]
The display terrain correction 132 issues a command for painting the area surrounded by the projected nearest neighbor vertex row 5002 and the display screen lower boundary 5003 with a terrain color corresponding to the viewpoint position elevation. As a result, the lack of terrain polygons that occur at the bottom of the screen does not occur, so the display quality can be improved.
[0088]
【The invention's effect】
As described above, in the three-dimensional map display device of the present invention, the above-described means is applied to specially delete the hidden surface of the map data displayed on the topographic map, that is, road data, background data, character / symbol data, and the like. It is possible to process completely and quickly without hardware. Furthermore, since the operation is performed so as to eliminate the missing polygons on the terrain surface, the display quality can be improved.
[Brief description of the drawings]
FIG. 1 is a diagram showing a three-dimensional map display example in the present invention.
FIG. 2 is a diagram showing each component unit of the navigation device.
FIG. 3 is a diagram illustrating a hardware configuration of an arithmetic processing unit.
FIG. 4 is a diagram illustrating a functional configuration of an arithmetic processing unit.
FIG. 5 is a diagram showing a functional configuration of map display means.
FIG. 6 is a diagram for explaining coordinate conversion means.
FIG. 7 is a diagram for explaining terrain mesh calculation means.
FIG. 8 is a flowchart for explaining the terrain mesh calculation means.
FIG. 9 is a diagram for explaining hidden surface presence / absence determining means;
FIG. 10 is a diagram for explaining map data dividing means.
FIG. 11 is a diagram showing a display example of character string data.
FIG. 12 is a flowchart for explaining character string processing means.
FIG. 13 is a diagram showing a memory configuration example of map data storage means.
FIG. 14 is a flowchart for explaining map data storage means;
FIG. 15 is a flowchart for explaining the drawing unit 58;
FIG. 16 is a diagram for explaining the drawing unit 58;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Arithmetic processing part, 2 ... Output device, 3 ... Memory | storage means, 4 ... Input device, 5 ... Wheel speed sensor, 6 ... Geomagnetic sensor, 7 ... Gyro, 8 ... GPS receiver, 9 ... In-vehicle LAN device, 21 ... CPU, 22 ... RAM, 23 ... ROM, 24 ... DMA, 25 ... Drawing processor, 26 ... Unified memory, 27 ... Color palette, 28 ... A / D converter, 29 ... SCI, 30 ... PIO, 31 ... Counter, 41 ... User operation analysis means, 42 ... Current position calculation means, 43 ... Map matching means, 44 ... Map data reading means, 45 ... Map display means, 46 ... Menu display means, 47 ... Display processing means, 50 ... Map data request Means 51: Terrain mesh calculation means 52 ... Coordinate conversion means 53 ... Hidden surface presence / absence judging means 54 ... Map data dividing means 55 ... Character string processing means 56 ... Map data Memory means 57 ... Projection conversion means 58 ... Drawing means 70 ... Visible area computing means 71 71 Terrain mesh size calculation 72 ... Terrain mesh generation 73 ... Minimum elevation extraction 74 ... Visible area correction 75 ... Elevation value Calculation: 80 ... Map data acquisition means, 81 ... Terrain mesh position calculation means, 82 ... Column determination means, 83 ... Interpolation point generation means, 91 ... Character string data acquisition, 92 ... Overlapping determination, 93 ... Character string position determination, 94 ... character string position correction, 95 ... character string drawing position correction, 100 ... management table, 101 ... map data storage memory, 110 ... initialization, 111 ... divided map data acquisition, 112 ... stored data determination, 113 ... start address setting, 114 ... Branch address correction, 115 ... Projection conversion, 116 ... Command buffer write, 117 ... End address setting, 118 ... End determination, 130 ... Surface treatment drawing, 131 ... display topographical determination, 132 ... display terrain correction.

Claims (5)

Elevation data composed of elevation values at each vertex of the mesh divided at a predetermined interval and map data are read from the storage medium, and a 3D topographic map overlooking from a predetermined viewpoint is generated from the elevation data, and the map is converted to a 3D topographic map In a three-dimensional map display device that displays data in an overlapping manner,
Topographic mesh calculation that calculates the coordinate value of each vertex constituting a rectangular or triangular terrain mesh that represents a terrain surface from elevation data that exists in the visible area of the map displayed on the display screen from a predetermined viewpoint Means,
Map data dividing means for dividing the map data to match each terrain mesh,
A drawing means for drawing map data divided on the terrain mesh;
A hidden surface presence / absence determining means for determining whether a hidden surface exists within the display range;
When the hidden surface presence determining means determines that a hidden surface exists, the map data divided by the map data dividing means is stored, and when the hidden surface presence determining means determines that there is no hidden surface, the map data dividing means does not divide And a map data storage means for storing the map data. The three-dimensional map display device according to claim 1,
A three-dimensional map display device having a terrain mesh size calculating means for determining a size of a terrain mesh according to a viewpoint height. The three-dimensional map display device according to claim 1,
A three-dimensional map display device comprising terrain mesh size calculating means for determining the size of a terrain mesh from a depression angle at which the map is looked down from a viewpoint. The three-dimensional map display device according to claim 1,
A three-dimensional map display device comprising terrain mesh size calculating means for determining the size of the terrain mesh using the viewpoint height and depression angle as parameters. Elevation data composed of elevation values at each vertex of the mesh divided at a predetermined interval and map data are read from the storage medium, and a 3D topographic map overlooking from a predetermined viewpoint is generated from the elevation data, and the map is converted to a 3D topographic map In a three-dimensional map display device that displays data in an overlapping manner,
Topographic mesh calculation that calculates the coordinate value of each vertex constituting a rectangular or triangular terrain mesh that represents a terrain surface from elevation data that exists in the visible area of the map displayed on the display screen from a predetermined viewpoint Means,
Map data dividing means for dividing the map data to match each terrain mesh,
A drawing means for drawing map data divided on the terrain mesh;
A hidden surface presence / absence determining means for determining whether a hidden surface exists within the display range,
A three-dimensional map display device, wherein map data dividing means divides map data into terrain mesh units when it is determined by a hidden surface presence / absence determining means that a hidden surface exists.

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