JP2006215888A - Drawing method using computer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To propose a drawing method more rapidly performing visual field decision to image information to rapidly draw even a large object. <P>SOLUTION: In this drawing method, coordinate information imparted with altitude information in each vertex of a prescribed grid is converted into a plurality of blocks, it is decided whether center coordinates of the block is within a visual field or not to perform the drawing. A group of the plurality of blocks that is the coordinate information wherein the altitude information is thinned out is generated, assignment is performed correspondingly to a range of a distance between the center coordinates of the block and a viewpoint, the distance between the center coordinates of the block and the viewpoint is actually found, and the block of the block group assigned correspondingly to the range between the viewpoint and the center coordinates of the belonging block is assigned to perform the drawing. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a drawing method using a computer, and more particularly to a method for drawing with accuracy according to the distance from a viewpoint.

  As a background art of the present invention, there is a landscape simulation. This landscape simulation is the creation of buildings and surrounding scenery using CG (Computer Graphics). Several methods have been proposed for constructing a landscape simulation. Here, a method for constructing a landscape simulation using an aerial photograph will be described from the relationship with the present invention.

  Aerial photographs that overlap each other are taken from an aircraft with an aerial camera equipped with an FMC device. The photographed aerial photograph negative file is converted into a digital image by a scanner equipped with a CCD sensor. Since the resolution of the scan affects the accuracy of the data to be created, for example, a negative film of 23 [cm] × 23 [cm] is scanned at 20 [μm].

  A digital image is read out to a computer and displayed on a display so that a person can view stereoscopically. The orientation is performed by correcting the distortion of the camera lens and obtaining the mutual relationship between a plurality of aerial photographs taken. Next, a point whose plane position and height are clearly known is selected from the antiaircraft sign and the topographic map, and is associated with the position on the aerial photograph as a reference point. This association is calculated using the bundle method, and a model similar to the ground according to geodetic coordinates is created on the computer by obtaining the position and tilt of the photographed camera.

From this created model, three-dimensional terrain data is manually acquired using a digital plotter. The terrain data is represented by a Triangulated Irregular Network (TIN), and is created by providing many breaklines at slope transformation points such as roads, ridges, and valleys. Also, 3D data such as current houses and bridges are acquired from the model. This random point array irregular triangle network model is a form of digital elevation model (Digital Elevation Model; DEM). Besides, it is a bilinear surface model of lattice point array, TIN model of contour line, bilinear surface of cross section or There is a TIN model. These models are familiar with “Spatial Information Engineering” (Shunji Murai, Japan Surveyor Association). In the embodiment of the present invention, a bilinear curved surface model having a lattice point arrangement is used.
An orthophoto projection aerial photograph (orthophoto) is created using the acquired three-dimensional data. The orthophoto is consistent with the topographic map and can accurately measure the distance, area, and direction.

  The above terrain data, existing structure data, and orthophotos will be integrated to build a landscape simulation. Specifically, the computer reads terrain data, current structure data, and orthophoto, and displays a three-dimensional CG on the display. The computer generates a model based on the terrain data that is the coordinate information, and texture maps the orthophoto that is the image information to the generated model. Of these, only what is actually projected on the display is projected onto a projection plane (view window) showing a virtual field of view from the viewpoint. For example, even if there is an object called A and an object called B, if the object A is not in the field of view, it is not drawn and only the object B in the field of view is drawn.

  The background art is configured as described above, and the drawing apparatus constructed by reading the drawing software into the computer determines whether or not the coordinates are necessary for drawing one by one. Since the image information is texture-mapped after the coordinate determination is completed, a large number of instructions are required in the determination portion, which causes a bottleneck and takes a long time to update the drawing. From the viewpoint of the user side, it means that the drawing cannot catch up with the movement of the viewpoint and a continuous image or moving image is not smoothly displayed on the display. This may be dealt with if the performance of the hardware is improved, but the same problem occurs when processing coordinate information and image information with higher accuracy. Furthermore, it is good if all the coordinate information and image information can be loaded onto the main memory, but if the area allocated to the drawing device is not enough, the OS (Operating System) that manages the entire computer performs paging. (In some cases, the drawing apparatus, not the OS, performs such processing), there is a problem that it takes time to process and falls into a situation that cannot be seen very much.

  The present invention has been made to solve the above-described problems, and has an object to propose a drawing method that can quickly determine a visual field regarding coordinate information and can draw a large object quickly. To do.

(Claim 1)
The method according to the present invention includes a step of creating a first lump group by dividing coordinate information, in which elevation information is given for each vertex of a predetermined grid, into a rectangular lump consisting of a predetermined number of vertices and not overlapping as regions. A step of deleting the elevation information of the vertices from the lump group at equal intervals to create a new lump group, and a lump group corresponding to the range of the distance between the first reference coordinate of the lump and the viewpoint is set as the first reference of the lump A step of finding and assigning the distance between the coordinates and the viewpoint, a determination step of determining whether or not the second reference coordinate in the block is in the field of view, and an assignment if it is determined in the determination step Drawing based on the lump of the lump group being performed, and these steps are performed by the computer. As described above, according to the present invention, coordinate information to which altitude information is given for each vertex of a predetermined grid is made into a plurality of chunks, and it is determined whether or not the second reference coordinates of the chunk are in the field of view. Compared with the conventional method of drawing and determining whether or not all vertices of a predetermined grid are in the field of view, the number of processes performed by the computer is greatly reduced and drawing can be performed at high speed. Also, a plurality of lump groups, which are coordinate information from which altitude information is thinned out, are generated and assigned corresponding to the range of the distance between the first reference coordinates of the lump and the viewpoint, and the first reference coordinates of the lump actually Is obtained by assigning a lump of a lump group corresponding to the range of the distance between the first reference coordinate of the lump and the viewpoint, and as the distance from the viewpoint gets closer, the altitude information Will be drawn using a lump that lacks elevation information as the distance from the viewpoint increases, in other words, a part with high accuracy is required for a part that requires accuracy, A portion with low accuracy is applied to a portion where accuracy is not required, and the amount of information to be processed is reduced according to human visual acuity, and the computer can draw at high speed. When the coordinate information is formed of a predetermined number of vertices and divided into rectangular chunks that do not overlap as a region, the vertices on the outer periphery of the chunk may or may not be shared with adjacent chunks. The reference coordinates in the lump are coordinates for determining whether the coordinates in the lump are in the field of view. The first reference coordinates in the lump and the second reference coordinates in the lump are preferably not different for each lump, for example, the center coordinates of the lump and the coordinates of the vertices of the rectangle formed by the lump. Further, not only a single coordinate but also four vertices are determined, and when it is determined that at least one vertex is in the field of view, it can be determined that a part of the cluster is in the field of view. The first reference coordinate in the lump and the second reference coordinate in the lump may be the same coordinate.

(Claim 2)
In addition, the method according to the present invention is a method in which the computer makes a determination by enlarging the range of the visual field in the determination step as necessary. As described above, in the present invention, when determining whether or not the central coordinates of a lump enter the field of view, the field of view is widened unlike the actual field of view, and the field of view that may be lost by determining for each lump. In this case, it is possible to reliably draw a portion that needs to be drawn.

(Claim 3)
Further, according to the method of the present invention, if necessary, the step of the computer deleting the altitude information of the vertices from the lump group at equal intervals to create a new lump group may be performed a plurality of times including the first lump group. Then, the lump group generated including the first lump group or the lump of the lump group is stored as a file in the storage means. As described above, in the present invention, the elevation information is deleted from the first block group to generate the second block group, the elevation information is deleted from the second block group, and the third block group is generated. Multiple clusters are created and stored as files in an external storage device such as a hard disk drive, magneto-optical disk drive, CD-ROM drive, or DVD-ROM drive other than the main storage device. The area on the main memory is not significantly occupied. If you occupy a large area of the main storage device, it will affect the processing of other devices mounted on the computer, and will greatly affect the response when paging occurs. It is better to reduce the occupied area.

(Claim 4)
In addition, the method according to the present invention increases the distance between the first reference coordinates of the lump and the field of view and the first reference coordinates in different lumps when the viewpoint and the field of view are changed as necessary. Including a step of generating and assigning new lumps by deleting the elevation information of the vertices from the lumps of the currently assigned lumps at regular intervals when they belong to the range of distance from the viewpoint, Is what you do. As described above, in the present invention, when a less accurate lump is required, a lump group lump that is assigned by deleting the altitude information from the lump group lump on the main storage device is generated, High-speed drawing can be realized without an input / output process requiring a considerable processing time.

(Claim 5)
Further, the method according to the present invention reduces the distance between the first reference coordinate of the lump and the field of view and changes the first reference coordinate and the viewpoint of a different lump when the viewpoint and the field of view are changed as necessary. And a step of reading out and assigning a lump group or a lump of lump group corresponding to the distance range between the first reference coordinates in the filed lump and the viewpoint, Is what the computer does. As described above, in the present invention, when a block with higher accuracy is required, the block of the corresponding block group that has been filed is read, and drawing with appropriate accuracy is held. When a block with higher accuracy than the block on the main memory is required, the already deleted altitude information cannot be restored, and therefore appropriate drawing can be performed by reading from the external storage device.

(Claim 6)
Further, in the method according to the present invention, the second reference coordinate in the lump is the center coordinate of the lump in the determination step as necessary. In this way, since it is determined whether or not the second reference coordinate of the lump is in the field of view, it is possible to determine more quickly than to determine a plurality of points, and when determining with one point In addition, the center coordinate is preferable as a point for determining whether or not the coordinate block is actually in the field of view. As a preferable reason, when judging from one point, if any one of the vertices is selected, a portion away from the vertex to be judged in the chunk is not drawn and there is a high possibility that it is lost. If it is the center, even if it is a part away from the center, it is only half the distance of the diagonal line, and it is unlikely to be lost as a probability theory. .

(Claim 7)
Further, the apparatus according to the present invention creates a first lump group by dividing coordinate information, which is given altitude information for each vertex of a predetermined grid, into a rectangular lump consisting of a predetermined number of vertices and not overlapping as a region. A lump group corresponding to the range of the distance between the lump dividing unit, the thinning unit that deletes the elevation information of the vertices from the lump group at equal intervals to create a new lump group, and the first reference coordinate in the lump and the viewpoint A distance calculation unit that assigns the lump by obtaining a distance between the first reference coordinate in the lump and the viewpoint, a determination unit that determines whether the second reference coordinate in the lump is in the field of view, and the determination A drawing unit that draws a lump determined to be in the field of view by the unit, and the thinning unit forms a plurality of lump groups including the first lump group.

(Claim 8)
Further, the program according to the present invention creates a first lump group by dividing coordinate information, which is given altitude information for each vertex of a predetermined grid, into a rectangular lump consisting of a predetermined number of vertices and not overlapping as a region. A lump group corresponding to the range of the distance between the lump dividing unit, the thinning unit that deletes the elevation information of the vertices from the lump group at equal intervals to create a new lump group, and the first reference coordinate in the lump and the viewpoint A distance calculation unit that assigns the lump by obtaining a distance between the first reference coordinate in the lump and the viewpoint, a determination unit that determines whether the second reference coordinate in the lump is in the field of view, and the determination A computer is operated as a drawing unit that draws a lump determined to be in the field of view by the unit, and the thinning unit creates a plurality of lump groups including the first lump group.

Embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention can be implemented in many different modes and should not be construed as limited to the description of the present embodiment.
In this embodiment, an apparatus to which the method is mainly applied will be described. However, as will be apparent to those skilled in the art, the present invention can also be implemented as a computer-usable program. Therefore, the present invention can take an embodiment as hardware, an embodiment as software, or an embodiment of a combination of software and hardware. The program can be recorded on any computer-readable medium such as a hard disk, CD-ROM, optical storage device, or magnetic storage device. Similarly, it can be implemented as a system.

  The drawing apparatus according to the present embodiment is mounted on a computer and includes a display 30, a keyboard 40, and a mouse (not shown) in addition to the computer main body. Peripheral devices other than the computer main body can be added as appropriate. For example, by applying a joystick or a joypad, the virtual space can be operated with higher operability.

[Description of drawing device configuration]
As shown in FIG. 1, the drawing apparatus according to the present embodiment is a module that is mounted by a normal drawing apparatus. The drawing information in the main storage device 22 or the external storage device 21 (meaning information related to general drawing). In addition to the drawing unit 15 for drawing), the block dividing unit 11 that divides the coordinate information given the elevation information for each vertex of the predetermined grid into a rectangular block consisting of a predetermined number of vertices and not overlapping as a region, The thinning unit 12 which deletes the altitude information of the vertices from the chunks of n chunks at equal intervals to create the (n + 1) th chunk group, and the nth chunk group corresponding to the range of the distance between the central coordinates of the chunk and the viewpoint The distance calculation unit 13 assigns the lump by obtaining the distance between the center coordinate of the lump and the viewpoint, and the determination unit 14 that determines whether or not the center coordinate of the lump is in the field of view. In addition to the block division unit 11, the thinning unit 12, the distance calculation unit 13, the determination unit 14, and the drawing unit 15, an input unit 16 that outputs an input signal from an input device such as a keyboard 40 to the inside of the computer, and a display 30 And an output unit 17 that outputs an output signal to the output device from inside the computer. Normally, the input unit 16 and the output unit 17 are carried by the OS. The drawing apparatus recognizes that there is an input signal in response to a message from the OS, receives the input signal, processes it, throws a message to the OS, and the output signal is received. Informs that there is an output and outputs an output signal. When these processes are implemented by programming, the API (Application Program Interface) of the OS is used.

  The drawing information drawn by the drawing apparatus is coordinate information for which altitude information is given for each vertex of a predetermined grid. In spatial information engineering, the digital terrain model (abbreviated as DTM) is a model that numerically expresses terrain features such as elevation, slope, slope, orientation, and water system, and the information of the digital terrain model is called DTM data. . In this DTM, a model specialized only in elevation data is a digital elevation model (Digital Elevation Model; DEM for short). In the present embodiment, DEM data is used as drawing information, and square lattice mesh data is used among the DEM data. In the present embodiment, square lattice mesh data is used in the DEM data, but other types of DEM data may be used. However, in the case of mesh data such as a square lattice (same intervals are acceptable), the decimation unit 12 deletes the altitude information at equal intervals, and the newly generated DEM data of the lump group also has different intervals. However, since the mesh data is a square lattice, there is a merit that variations in accuracy do not occur.

  The lump dividing unit 11 divides DEM data, which is coordinate information for which altitude information is given for each vertex of a predetermined grid, into a rectangular lump composed of a predetermined number of vertices and not overlapping as a region. Although it does not overlap as a region, it may overlap as a vertex, but in this embodiment, a cluster is configured as shown in FIG. 2 without overlapping. In FIG. 2, the lump is composed of 4 × 4 and 16 vertices in total. However, FIG. 2 shows a part of DEM data. Moreover, what is called a lump in this embodiment may be called a block. The DEM data is normally (power of 2) × (power of 2), and the chunk is also (power of 2) × (power of 2), so there is no remainder. If a remainder is generated, it can be dealt with by a method of deleting the remainder and a method of adding coordinates given appropriate altitude information.

  The thinning unit 12 deletes the altitude information of the vertices from the n-th lump group at equal intervals to create an n + 1-th lump group. n is a positive natural number. Also, as the lump group is larger, the altitude information is deleted and the image information becomes less accurate. Eliminating elevation information at equal intervals in this way is nothing but creating a mass group of DEM data without bias. The thinning unit 12 deletes the elevation information of the vertices at equal intervals from the lumps shown in FIG. Furthermore, the lump of FIG. 3 was processed by the thinning-out portion to obtain a lump consisting of a total of 4 vertices as shown in FIG. In this way, when one side of the cluster consists of vertices that are powers of 2, the total number of vertices of the cluster is halved each time thinning is performed. Since it is sufficient that thinning can be performed at equal intervals, thinning can be performed at 1/4 times, and the accuracy ratio can be adjusted. Further, in the present embodiment, the plurality of generated mass groups are filed and stored in the external storage device 21. As a result, the chunks to be loaded on the main storage device 22 are limited, and the chunk group or chunk group chunks filed as necessary can be loaded onto the main storage device 22 for use. The area can be released without securing most of the storage device 22 and by unloading it when it is unnecessary.

The distance calculation unit 13 assigns the n-th lump group lump corresponding to the distance range between the lump center coordinates and the viewpoint by determining the distance between the lump center coordinates and the viewpoint. As shown in FIG. 5, the range of the distance d between the central coordinates of the lump and the viewpoint is defined as d ₁ > d, d ₂ > d ≧ d ₁ , d ₃ > d ≧ d 2, d ₄ > d ≧ d ₃ , d _5. > D ≧ d4,..., And corresponding to the respective ranges, the DEM data of the first lump group, the DEM data of the second lump group, the DEM data of the third lump group, the fourth lump DEM data of the group, DEM data of the fifth mass group,... Are assigned. In FIG. 5, the thickness of the DEM data of the first lump group is the thickest. This indicates that the DEM data has a large amount of information and is highly accurate. That is, it shows that there is a lot of elevation information corresponding to the vertex.

  The determination unit 14 determines whether the central coordinates of the lump are in the field of view. The technique for determining whether or not the central coordinates are in the field of view is not an essential part of the present invention, and various algorithms exist as well-known techniques in the field of CG (Computer Graphics), and those skilled in the art can implement them appropriately. Since this is possible, only an example will be described here. Judgment is made based on whether or not the angle between the viewpoint direction and the straight line connecting the viewpoint and the center coordinates falls within the viewing angle. In this case, the calculation can be performed using the cosine theorem because the lengths of all sides are known, but other calculation methods may be used. The specific calculation using the cosine theorem is obtained because the starting point of the unit vector in the line-of-sight direction is the viewpoint and the end point is also the unit vector, and there is also the center coordinate of the lump. The obtained cosine theorem reveals how many times it is tilted from the line-of-sight direction, and it is possible to determine whether or not it enters the field of view by comparing the tilt angle with the viewing angle. In addition to this, a projection plane (view window) is prepared separately from the viewpoint, and objects in the virtual space in the area that enters the projection plane from the viewpoint are displayed on the display. Therefore, it can be determined whether or not the straight line connecting the viewpoint and the center coordinates enters the field of view based on whether or not it intersects the projection plane (see FIG. 7). Further, in the method used in the present embodiment for determining whether the angle between the viewpoint direction and the straight line connecting the viewpoint and the center coordinates falls within the viewing angle, the viewing angle is slightly expanded. As a result, it is possible to avoid the problem that a part of the lump that is determined not to enter the field of view at the part in the field of view is actually in the field of view and is not drawn by this determination. When the latter method is applied, it can be dealt with by increasing the projection plane.

  The drawing unit 15 draws drawing information. Here, the drawing information is DEM data of a lump determined to be in the field of view by the determination unit. Moreover, even if only this DEM data is drawn, the object is three-dimensionally represented in the target virtual space. However, by mapping the orthophoto generated through the process shown in the background art, it is more realistic. A virtual space close to the world can be drawn. Texture mapping is not an essential part of the present invention, and various algorithms exist as well-known techniques in the field of CG (Computer Graphics), and those skilled in the art can implement them appropriately. In addition to texture mapping, a solid texture can also be applied. Furthermore, in the present embodiment, the orthophoto is converted into a JPEG data format, and a plurality of JPEG format orthophotos are generated from those having a low compression rate to those having a high compression rate. More preferably, orthophotos having image quality corresponding to the number of chunk groups are prepared, and orthophotos having image quality corresponding to the chunks are read in accordance with the chunk groups, and texture mapping is performed (see FIG. 6). As a result, the image quality of the orthophoto that is texture-mapped in proportion to the accuracy of the altitude information is also drawn in proportion. Here, JPEG is not an essential part of the present invention, and various algorithms exist as well-known techniques in the field of image processing and can be appropriately realized by those skilled in the art. Therefore, only one example will be briefly described here. To do. Original image data is first blocked into 8 × 8 pixels, converted by DCT (Discrete Cosine Transform), quantized, and encoded to obtain compressed image data. Although JPEG is used here, other methods may be used as long as the degree of image quality and the amount of data can be adjusted. For example, PNG (Portable Network Graphics) can be used. Further, although orthophoto is used, other image information may be used, such as satellite photographs, CAD diagrams, and maps.

  In addition, when drawing is performed by the drawing unit 15, adjacent chunks usually belong to the same chunk group, but a chunk of a certain chunk group and a chunk of a different chunk group may be adjacent to each other. This occurs when the distance between the viewpoint and the central coordinates of a lump belongs to a range of distances between the viewpoint and the central coordinates of the lump that are different from the distance between the viewpoint and the central coordinates of an adjacent lump. In this case, the vertices of the DEM data of the block having the altitude information (having highly accurate coordinate information) at a small interval are connected to the vertices of the DEM data of the adjacent block (FIG. 4B). )), It can be dealt with by forming a triangle. DEM data is a square lattice, but when it is actually drawn on a computer, it may be drawn as a triangular polygon, and there is no problem with drawing.

[Description of operation of drawing device]
First, when a user clicks an icon representing the drawing device displayed on the display 30 with the pointer over it, the drawing device is constructed on the computer. First, with respect to DEM data allocated in advance, the lump dividing unit 11 includes a predetermined number of vertices of coordinate information to which altitude information is given for each vertex of a predetermined grid, and rectangular blocks that do not overlap as regions. (Step 101. Refer to the flowchart of FIG. 8 below). It is determined whether or not the division is performed for all the vertices by the block dividing unit 11 (step 102. It is determined whether or not there are any remaining vertices). Starting with the first lump group (n = 1), the thinning unit 12 generates the n + 1 lump group from the nth lump group by deleting the altitude information at equal intervals (step 103). The generated n + 1-th mass group is converted into a file and stored in the external storage device (step 104). It is determined whether or not a preset N-th mass group has been generated and filed (step 105). If it is determined that it has been made, n is initialized to 1 (step 107). If it is determined in step 105 that the process has not been performed, n is incremented by 1 (step 106), and the process proceeds to step 103. If it is determined in step 102 that the processing has not been performed for all vertices, the process proceeds to step 101. After the processing in step 107, orthophotos corresponding to the nth cluster group are generated in JPEG format starting with the first cluster group (n = 1) (step 108, the larger n is). The compression rate is increased) and the file is stored in the external storage device 21 (step 109). It is determined whether or not an orthophoto corresponding to a preset N-th mass group has been generated and filed (step 110). If it is determined that it has been created, the rendering of the predefined process in step 200 is performed. Transition to processing. This drawing process will be described later. If it is determined in step 110 that the process has not been performed, n is incremented by 1 (step 111), and the process proceeds to step 108.

  The above steps 101 to 111 can be omitted because a file has been generated if, for example, the drawing apparatus is performed once when the drawing apparatus is first constructed on the computer. Further, in the case of a drawing apparatus that can be assigned to a plurality of DEM data, it may be performed once for each assigned DEM data.

  Next, the drawing process in step 200 will be described. The distance calculation unit 13 calculates the distance between the center coordinate and the viewpoint (usually starting from a block that includes or is close to the reference coordinates of the virtual space or object) (step 201). In accordance with the obtained distance, the distance calculation unit 13 assigns DEM data of the lump of the lump group (step 202). It is determined whether or not Step 201 and Step 202 have been performed for all the chunks (Step 203), and if it is determined that they have been performed, it is determined whether or not the determination unit 14 is within the field of view (Step 204). ). The drawing unit 15 draws the chunk determined to be within the field of view based on the DEM information of the chunk group already assigned to the chunk (step 205). Subsequently, texture mapping is performed on the orthophotos corresponding to the chunks of the chunk group for the model of the drawn chunk (step 206). Further, it is determined whether or not the step 204 has been performed for all the chunks (step 207). If it is determined that the block 204 has not been performed, the process proceeds to the step 204. If it is determined in step 203 that the process has not been performed, the process proceeds to step 201. If it is determined in step 207 that all the chunks have been made, it is determined whether or not the viewpoint and field of view have changed (step 208). If it is determined that a change has occurred, The process proceeds to step 201 based on the viewpoint and field of view where the fluctuation has occurred. If it is determined in step 208 that no change has occurred, it is determined whether or not the process has ended (step 209). If it is determined that the process has ended, the process ends. If it is not determined in step 209 that the process has ended, the process proceeds to step 208.

  In the above steps, the reading of the DEM data file and the JPEG orthophoto from the external storage device 21 is not mentioned, but it will be read when necessary. For example, it can be loaded when it is determined in step 205 and step 206 that it is not loaded on the main storage device 22. Alternatively, it can be loaded when it is determined that it is not loaded onto the main storage device 22 at the time of step 202. However, loading at step 205 and step 206 has no fear of loading a block outside the field of view, and the number of processes is reduced as a whole.

  As described above, according to the drawing apparatus according to the present embodiment, DEM data is converted into a plurality of chunks (may be referred to as blocks instead of chunks), and it is determined whether or not the central coordinates of such chunks are in the field of view. Compared with the conventional method for determining whether or not every vertex of a predetermined grid is in the field of view, the number of processes performed by the computer is greatly reduced, and the drawing can be performed at high speed. In addition, DEM data of multiple mass groups, which are coordinate information with altitude information thinned out, is generated, and the DEM data corresponds to the range of distance between the central coordinates of the mass and the viewpoint, and the actual center coordinates of the mass The distance between the viewpoint and the viewpoint is determined, and the chunks corresponding to the range of the center coordinates of the belonging chunk and the viewpoint are assigned and drawn. The closer the distance to the viewpoint is, the more elevation information is lost. If the distance from the viewpoint is increased, drawing is performed using a lump that lacks elevation information. In other words, high accuracy is required for parts that require high accuracy. A portion with low accuracy is applied to the portion that is not taken, so that the amount of information to be processed is reduced and the computer can draw at high speed.

  The lump dividing unit 11, the thinning unit 12, the distance calculating unit 13, the determining unit 14, and the drawing unit 15 illustrated in the present embodiment are examples of a module configuration. For example, the distance calculating unit 13 is set as the center coordinates of the lump. It is also possible to have a configuration in which the distance calculation unit for obtaining the distance between the viewpoint and the viewpoint, and the assignment unit for assigning the nth group of clusters corresponding to the range of the center coordinates of the cluster and the distance between the viewpoints can be used.

  In addition, when N in Step 107 is increased, a large number of mass groups can be generated and correspond to the range of distance, and the distance can be actually calculated and assigned, but when N is increased too much On the other hand, it should be noted that rapidity cannot be maintained due to frequent loading and unloading due to subdivision of the distance range.

  Further, the processing flow described in the present embodiment is an example. For example, as shown in FIG. 10, by performing the determination before step 201 as shown in FIG. As a result, the processing amount as a whole can be reduced. Furthermore, after assigning all the blocks, drawing and texture mapping can be performed at once.

[Extension using WWW]
In addition, since the drawing apparatus according to the present embodiment browses a Web page constructed on a computer, specifically, an HTML file, an image file, a music file, or the like is downloaded from the Internet, and a layout is analyzed and displayed. -It can also be constructed on a playback device (so-called browser or Web browser), and the binary data, DEM data, and ortho that constitute the rendering device from a Web server that is a device that has an information transmission function by WWW (World Wide Web) It is also possible to send a photo together with an HTML file to a browser via a network. The browser receives such information, displays HTML in the browser, constructs a drawing device with binary data, and can draw in the browser in the same manner as described above using DEM data and orthophoto. As a more specific configuration example, a dynamic library (Dynamic Link Library) is stored so that GL4JAVA can operate on a computer where a JAVA-compatible browser is built, and binary data (called Java bytecode is called from the Web server) (Intermediate code) is transmitted with the media type of application / x-java-applet, and the drawing device is constructed on the browser. In this case, all operations of the drawing apparatus are performed on the client side. However, a part or all of operations other than the drawing unit can be performed by the Web server using a Java servlet.

  In this way, when a drawing apparatus is constructed on a browser and the process of transmitting DEM data and orthophoto is performed, a considerable communication speed is required. However, since the computer on which the browser is built is not necessarily in such an environment, the already thinned DEM data can be transmitted from the Web server side to the browser side. In this case, it is preferable to transmit DEM data having a data amount that matches the communication speed. Specifically, high-quality DEM data is transmitted at a high communication speed, and low-quality DEM data (the number of thinnings is large) at a low communication speed.

Further, the data to be transmitted to the browser side can be compressed on the WWW server side and decompressed on the browser side using a compression method such as JPEG.
The data once received on the browser side can also be stored on the computer on which the browser is built. More specifically, it can be stored as cache data using the browser's cache function.

A comparative experiment between the drawing apparatus according to the embodiment and a conventional drawing apparatus was performed. As for the environment of the computer, the CPU is Pentium III 750 [Mz], the memory (main storage device) is RIMM (Rambus Inline Memory Module) 1 [GB], and the graphic board is Tornado 3000 of E & S.
In this environment, as shown in FIG. 11 (a), using the DEM data whose square lattice coordinates are (0, 0) to (1024, 1024), the line of sight shown in the figure from the viewpoint (512, 0). Drawing in the case of the direction was performed for each lump size and the drawing processing time was measured. The field of view studied was 30 [degrees], 60 [degrees], 90 [degrees], and 120 [degrees], and the sizes of the masses tested were 1 × 1, 2 × 2, 4 × 4, 8 × 8, 16 X16, 32x32, 64x64 and 128x128.

  FIG. 11B shows the experimental result under the above conditions. The time required for drawing all DEM data at a viewing angle of 30 degrees was 0.031 [seconds]. According to FIG. 11 (b), with respect to a viewing angle of 30 degrees, 1 × 1, 2 × 2, 4 × 4, 8 × 8, 16 × 16, 32 × 32, 64 × 64, and 128 × It can be seen at 128 that the drawing speed is greatly improved. The same was found for other viewing angles.

  The drawing method according to the present invention can be applied to landscape simulation, and is an information system that handles digitized map data and data related to positions such as statistical data and attribute information of positions in an integrated manner. It can be applied to a three-dimensional GIS (Geographical Information System). High-speed drawing is realized by landscape simulation using this drawing method, simulation of the current situation, simulation when the planned structure is taken in, simulation by past reproduction, night view simulation, wind direction wind speed simulation, simulation of dam inundation depth , River inundation simulation etc. can be grasped more easily.

It is a block block diagram of the drawing apparatus which concerns on embodiment of this invention. It is explanatory drawing of the division | segmentation and thinning-out of DEM data which concern on embodiment of this invention. It is explanatory drawing of the thinning-out of DEM data which concerns on embodiment of this invention. It is explanatory drawing of the thinning-out of DEM data which concerns on embodiment of this invention. It is a correspondence between the DEM data of each lump group and the range of distance according to the embodiment of the present invention. It is a correspondence between DEM data of each lump group and orthophoto according to the embodiment of the present invention. It is explanatory drawing of determination of the visual field which concerns on embodiment of this invention. It is a flowchart figure of the drawing apparatus which concerns on embodiment of this invention. It is a flowchart figure of the drawing apparatus which concerns on embodiment of this invention. It is a flowchart figure of the drawing apparatus which concerns on embodiment of this invention. It is experiment explanatory drawing and experiment result which concern on the Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Block division part 12 Thinning part 13 Distance calculating part 14 Judgment part 15 Drawing part 16 Input part 17 Output part 21 External storage device 22 Main storage device 30 Display 40 Keyboard

Claims (8)

The step of creating the first lump group by dividing the coordinate information for which the altitude information is given for each vertex of the predetermined grid from a predetermined number of vertices into non-overlapping rectangular blocks, and at equal intervals from the block group Deleting the elevation information of the vertices to create a new lump group, and determining a lump group corresponding to the range of the distance between the first reference coordinate and the viewpoint in the lump between the first reference coordinate and the viewpoint in the lump A step of determining and assigning a distance; a determination step of determining whether or not the second reference coordinate in the block is in the field of view; and a block group assigned if it is determined to be included in the determination step Drawing on the basis of a lump of blocks, the computer performing these steps. The method according to claim 1, wherein the determination is performed by enlarging a range of the visual field in the determination step. The computer deletes the elevation information of the vertices from the lump group at equal intervals to create a new lump group, including the first lump group. The method according to claim 1, wherein the lump group or each lump of the lump group is stored as a file in the storage means. When the viewpoint or field of view changes, the current assignment is made when the distance between the central coordinates of the chunk and the field of view becomes longer and belongs to the range of the distance between the first reference coordinate in different chunks and the viewpoint. The method according to claim 1, further comprising the step of generating and assigning new lumps by deleting vertex elevation information from the lumps of lumps being created at equal intervals, wherein the computer performs this step. When the viewpoint and field of view change, the distance between the central coordinates of the chunk and the field of view becomes shorter and it belongs to the range of the distance between the central coordinates of the different chunk and the viewpoint. 4. The method according to claim 3, further comprising the step of reading out and assigning a chunk or a chunk of chunks corresponding to a range of distances between the first reference coordinates and the viewpoint, wherein the computer performs this step. The method according to claim 1, wherein, in the determining step, the second reference coordinates in the lump are center coordinates of the lump. Coordinate information for which altitude information is given for each vertex of a predetermined grid is made up of a predetermined number of vertices, divided into rectangular blocks that do not overlap as regions, a block division unit that creates the first block group, etc. The thinning unit that deletes the elevation information of the vertexes at intervals and creates a new lump group, and the lump of lump group corresponding to the range of the distance between the first reference coordinate in the lump and the viewpoint is the first lump in the lump. A distance calculation unit that obtains and assigns a distance between the reference coordinates and the viewpoint, a determination unit that determines whether or not the second reference coordinates in the lump are in the field of view, and the determination unit determines that the distance is in the field of view A drawing unit for drawing the lump
The apparatus in which the thinning-out unit creates a plurality of lump groups including the first lump group. Coordinate information for which altitude information is given for each vertex of a predetermined grid is made up of a predetermined number of vertices, divided into rectangular blocks that do not overlap as regions, a block division unit that creates the first block group, etc. The thinning unit that deletes the elevation information of the vertexes at intervals and creates a new lump group, and the lump of lump group corresponding to the range of the distance between the first reference coordinate in the lump and the viewpoint is the first lump in the lump. A distance calculation unit that obtains and assigns a distance between the reference coordinates and the viewpoint, a determination unit that determines whether or not the second reference coordinates in the lump are in the field of view, and the determination unit determines that the distance is in the field of view A program in which a computer is operated as a drawing unit for drawing a lump, and the thinning unit creates a plurality of lump groups including the first lump group.

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