JP2756066B2 - Ground surface display method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a terrain display method, and more particularly to a method of displaying terrain three-dimensionally using a three-dimensional image display device, in accordance with the number of vertices constituting the terrain to be displayed. And a ground surface display method for changing the display method.

[0002]

2. Description of the Related Art A display method for generating an image of a three-dimensional model from three-dimensional terrain model data includes, for example, James.
D. Foley, Anries Van Dam, translated by Atsumi Imamiya
"Computer Graphics" Japan Computer Association, pp. 591-595 (1984), or by Echiro Nakamae
"Computer Graphics" Ohmsha, pp. 168
170 (1987), there are a glow shading method, a texture mapping method, and the like.
The glow shading method is to generate a three-dimensional model image by determining the lightness of each vertex of a polygon surface constituting a three-dimensional model, linearly complementing the lightness between the vertices and shading the polygon. It is. In the texture mapping method, shading is performed by mapping image data on a surface constituting a three-dimensional model to generate an image of the three-dimensional model.

[0003] Further, as a conventional technique for three-dimensionally displaying the terrain using a three-dimensional image display device, there is Kaned.
a K. Kato F. Nakamae E. Nishita T. Tanak
a H. Noguchi T. “Three Demensional Terra
in Modeling and Display for Enveronment
al Assessment ", Computer Graphics, Vol.2
3, No. 3 (1989), pp. 207-214. The technique described in this book maps an image such as an aerial photograph to a terrain model based on map data. Further, in the technique, after the perspective transformation, the size of the patch is made substantially constant regardless of the distance in the horizontal direction.

[0004]

Here, in the conventional terrestrial surface display method for three-dimensionally displaying the terrain as described above, the number of vertices constituting the terrain increases as the display target range becomes wider, and image generation is performed. However, there is a problem that the processing time for the process increases. Therefore, in such a case, the display processing cannot be completed within a predetermined time by the conventional ground surface display method. In order to solve this problem, a method has been proposed to reduce the number of vertices by thinning out the vertices constituting the terrain to be displayed, but this method can complete the display processing within a predetermined time. However, there is a problem that the image quality is deteriorated and a high-quality image cannot be generated.

As described above, in the conventional surface display method, the processing time for image generation increases when the image quality is improved, and the image quality decreases when the image generation processing time is shortened. There was a point.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and prevents an increase in processing time for image generation due to an increase in the number of vertices due to an increase in the terrain range to be displayed. In addition, it is an object of the present invention to obtain a ground surface display method for generating a high-quality three-dimensional model image in a short time by preventing a decrease in image quality due to a decrease in the number of vertices due to thinning out vertices constituting display terrain. .

[0007]

In order to achieve the above-mentioned object, a ground surface display system according to the present invention is a ground surface display system for displaying terrain three-dimensionally using an image display device. Terrain model data comprising vertex information, and means for incorporating pre-processed terrain images,
An information input unit for inputting viewpoint information such as a viewpoint position, a gazing point position, and a viewing angle necessary for generating a three-dimensional image, and a display region analysis for determining a topographic region to be displayed according to the viewpoint information input by the information input unit. and parts, as well as determining the thinning number of vertices from the vertex number of the terrain model data included in terrain area determined by the display area analyzer, thinning
When the number is small, the glow shading method is selected as the display method, and when the number of thinning is large, the display method determining unit selects the texture mapping method, and the terrain model is thinned according to the thinning number determined by the display method determining unit. A glow shading processing unit that generates a three-dimensional terrain image by glow shading using the data; a terrain model data thinned according to a thinning number determined by a display method determination unit; and the preprocessed terrain image. A texture mapping unit for generating a three-dimensional terrain image by texture mapping using the display unit; and a display unit for displaying an image generated by the glow shading processing unit or the texture mapping processing unit. .

[0008]

Therefore, according to the ground surface display method of the present invention, a terrain area to be displayed is determined from viewpoint information such as a viewpoint position, a gazing point position, and a viewing angle required for generating a three-dimensional image, and the terrain area is determined. From the number of vertices of the included terrain model data, the number of vertices to be thinned and the display method are determined, and a three-dimensional terrain image is generated by the glow shading method or the texture mapping method according to the determination. Even if the number of vertices to be widened and the number of vertices to be increased increases, the vertices are appropriately thinned out by the display method determination unit, thereby preventing an increase in processing time for image generation. Detailed terrain image
By texture mapping the top of the displayed terrain
Even if the points are thinned out, it is possible to prevent a decrease in image quality and generate a high-quality three-dimensional model image in a short time.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a functional configuration of a three-dimensional image display device according to the present embodiment that realizes the ground surface display method of the present invention.

In FIG. 1, a three-dimensional image display device according to the present embodiment has an information input unit 11 for inputting viewpoint information such as a viewpoint position, a gazing point position, and a viewing angle required for generating a three-dimensional image.
A display area analysis unit 12 that determines a topographic area to be displayed according to information such as viewpoint information input by the information input unit 11; and a topography that forms the topography of the display area obtained by the display area analysis unit 12. A display method determining unit 13 that determines the thinning number and display method of the vertices from the number of vertices of the model data, and when the thinning number is small by the display method determining unit 13, glow shading is selected as the display method. In this case, the glow shading processing unit 14 that generates a three-dimensional terrain image by glow shading using the terrain model data thinned out according to the thinning number determined by the display system determination unit 13, and similarly determines the display system. When the thinning number is large by the unit 13, the texture mapping is selected as the display method. A texture mapping processing unit 15 for generating a three-dimensional terrain image by texture mapping using the terrain model data and the terrain image thinned out according to the thinning number determined by the display method determination unit 13 in this case; Glow shading processing unit 14
Alternatively, it is constituted by a display unit 16 for displaying an image generated by the texture mapping processing unit 15.

The glow shading processing section 14
Is input with terrain model data 101 composed of information of vertices arranged in a grid, and the texture mapping processing unit 15 receives terrain model data 101 and a previously processed terrain image 102.

FIG. 2 is a flowchart showing the details of the processing performed by the display mode determination section 13 shown in FIG. First, the GRA shown in the flowchart of FIG.
UTV, MABIKI table, and LIMITOFG
Each term of RAU will be described. First, GRAUTV
Is the total number of vertices that can be processed within a predetermined time determined by design for glow shading. Also, MAB
The IKI table is a list of thinning numbers that can be thinned out at equal intervals in the terrain model data. In other words, possible thinning numbers are obtained from the number of vertical and horizontal vertices constituting the terrain model data, and the thinning numbers are calculated in ascending order of MABIK.
I1, MABIKI2,..., MABIKIi,.
.., MABIKIn, and are stored at the addresses 1, 2,..., I,..., N of the MABIKI table. Also, the decimation number 0 is set to MABIKI0
Is stored at address 0 of the MABIKI table as
Create an ABIKI table. In addition, LIMITO
FGRAU is the upper limit value of the thinning number for performing glow shading.

FIG. 3 is a diagram showing specific definition data of the terrain model data 101 in the three-dimensional image display device of the present embodiment. In FIG. 3, terrain model data 301
Indicates a predetermined ground surface area on the earth, and the predetermined area on the earth indicated by the terrain model data 301 is 16 areas A
k. Each divided region of the terrain model data 301 has a longitude difference of 7 minutes 30 seconds (450 seconds) and a latitude difference of 5 minutes (300 seconds). This divided 1
Assuming that each area is divided into 40 equal parts in the longitude direction and the latitude direction, one terrain area Ak is divided into 11 seconds 25 longitudes and 7 seconds 50 latitudes as shown in the model data 302. Therefore, the number of vertices in one area Ak is 41 × 4
1 = 1681. That is, to process one area, it is necessary to process a maximum of 1,681 vertices.
However, the vertices of the boundary of the area Ak are managed redundantly.

Next, the terrain image 102 will be described.
The terrain image 102 is divided and stored in an area Ak in the same manner as the terrain model data 101. The terrain image for each area Ak is terrain model data 101 without thinning.
To use a three-dimensional terrain image generated by glow shading.

FIG. 4 is a conceptual diagram showing a method of obtaining a display area from a viewpoint position, a gazing point position, and a viewing angle. In FIG. 4, a viewpoint position 401 and a gazing point position 402
A viewing angle 403 in the horizontal direction with respect to the viewpoint and a viewing angle 404 in the vertical direction with respect to the viewpoint are shown. And
The terrain range entering the field of view from the viewpoint position 401 is indicated by a chain line.

Next, the third embodiment of the present invention constructed as described above
The operation of the three-dimensional image display device will be described with reference to FIGS. First, in FIG. 1, the information input unit 11 receives a viewpoint position, a gazing point position required for generating a three-dimensional image from a user,
Enter viewpoint information such as viewing angle. Next, the display area analysis unit 12 determines the topographic area to be displayed as shown in FIG. 4 from the viewpoint information such as the viewpoint position, gazing point position, horizontal viewing angle, and vertical viewing angle input by the information input unit 11. obtains the latitude and longitude of the southwest end and north east edge, determine all area Ak contained in that region.

The display mode determination unit 13 determines the number of vertices to be thinned out from the number of vertices of the terrain model data 101 included in the terrain area determined by the display area analysis unit 12, and when the number of culls is small, the display method is used. When the glow shading method is selected and the number of thinnings is large, processing for selecting the texture mapping method is performed. Details of the processing are shown in FIG. That is, first
The index i of the ABIKI table is initialized (step 211). Next, MA from the MABIKI table
BIKIi is read (step 212), and the total number of vertices T
V is obtained (step 213). Since one of the regions Ak is composed of 41 × 41 = 1681 vertices,
In the case of the thinning number MABIKIi, the number of vertices is as shown in Expression (1). Therefore, the total number of vertices TV can be obtained by the calculation formula shown in Expression (2).

[0018] (40 / (MABIKI i +1) +1) 2 ... (1) TV = number of area Ak × (40 / (MABIKI i +1) +1) 2 ... (2) Next, the configuration of the terrain area to be displayed Then, the total number of vertices TV to be processed is compared with the number of vertices GRAUTV that can be processed within a predetermined time determined by design for glow shading (step 214). As a result of the comparison, when GRAUTV ≧ TV, the process proceeds to step 215 because all the vertices in the current thinning number can be processed within a predetermined time. On the other hand, when GRAUTV <TV, the total number of vertices in the current thinning-out number cannot be processed within a predetermined time.
A larger decimation number must be selected and the comparison process must be performed again. Therefore, in step 218, MA
Check if there is a value not yet referenced in the BIKI table (i equals n). If i is not equal to n, it means that there is a value to be further referred to, so 1 is added to the index i of the MABIKI table (step 219), and step 21 is performed again.
Return to 2. If i is equal to n, the comparison process has been completed for all values in the MABIKI table, and the process proceeds to step 215.

Next, the upper limit value LIMITOFGRAU of the thinning number for performing glow shading and the current thinning number M
ABIKIi is compared (step 215). Limi
When TOFGRU ≧ MABIKIi, even if the image is generated by glow shading, the deterioration of the image quality is within an allowable range. Therefore, glow shading is selected as the image generation method. In contrast, LIMITOFGR
When AU <MABIKIi, it indicates that the deterioration of the image quality in the display by glow shading exceeds the allowable range, and therefore the texture mapping is selected as the image generation method.

The glow shading processing section 14
Is a thinning number M when the display method determination unit 13 selects glow shading as the display method.
For each terrain model data for each area Ak according ABIKIi, reads terrain model data 101 in the vertical and horizontal MABIKI i pieces every generating an image of a three-dimensional topography with Gouraud shading. At this time, the decimation number MABI
When KIi is 0, no thinning is performed, and a terrain image is generated using all the data of the terrain model data 101.

When texture mapping is selected as the display mode in the display mode determination section 13, the texture mapping processing section 15 outputs the thinning number MABIKIi.
According to each terrain model data for each area Ak, vertically and horizontally MABIKI i pieces every reads the terrain model data 101, simultaneously reads out the terrain image corresponding to the region Ak from topographic image 102, the three-dimensional terrain by the texture mapping Generate an image.

The display unit 16 displays the terrain image generated by the glow shading processing unit 14 or the texture mapping processing unit 15.

[0023]

As described above, according to the ground surface display method of the present invention, a topographic region to be displayed is determined from viewpoint information such as a viewpoint position, a gazing point position, and a viewing angle necessary for generating a three-dimensional image. Then, based on the number of vertices of the terrain model data included in the terrain region, the number of vertices to be decimated and the display method are determined, and a three-dimensional terrain image is generated by a glow shading method or a texture mapping method according to the determination. With this configuration, even if the terrain range to be displayed is widened and the number of vertices to be targeted is increased, vertices that are equal to or more than the reference value are appropriately thinned out by the display method determination unit to prevent an increase in processing time for image generation. In addition, by performing texture mapping of a detailed terrain image, even if the number of vertices of the displayed terrain is reduced, the image quality is prevented from deteriorating, and a high-quality three-dimensional model is prevented. There is an effect that can generate Le images.

[Brief description of the drawings]

FIG. 1 is a block diagram of a three-dimensional image display device that realizes a ground surface display method according to an embodiment.

FIG. 2 is a flowchart illustrating details of processing performed by a display method determination unit 13 illustrated in FIG. 1;

FIG. 3 is a diagram showing an example of specific definition data of the terrain model data 101 shown in FIG.

FIG. 4 is a conceptual diagram showing a method for obtaining a display area from a viewpoint position, a gazing point position, and a viewing angle.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Information input part 12 Display area analysis part 13 Display method determination part 14 Glow shading processing part 15 Texture mapping processing part 16 Display part 101 Terrain model data 102 Terrain image

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G06T 15/50 G06T 17/50 JICST file (JOIS)

Claims (1)

(57) [Claims] 1. A terrestrial surface display method for displaying terrain three-dimensionally using an image display device, wherein terrain model data comprising information of vertices arranged in a grid and terrain images preprocessed are incorporated. Means for inputting viewpoint information necessary for generating a three-dimensional image, a display region analyzing unit for determining a topographic region to be displayed in accordance with the viewpoint information input by the information input unit, and a display region analysis A display method determination unit that determines the number of vertices to be thinned out from the number of vertices of the terrain model data included in the terrain area determined by the unit, and selects the glow shading method as the display method when the number of thinned out is small,
When the number of thinnings is large, a three-dimensional terrain image is formed by glow shading using a display method determining unit that selects a texture mapping method and terrain model data that is thinned according to the thinning number determined by the display method determining unit. A three-dimensional topographic image by texture mapping using the terrain model data thinned out according to the culling number determined by the display method determining unit and the preprocessed terrain image And a display unit for displaying an image generated by the glow shading processing unit or the texture mapping processing unit.