JP3218372B2 - 3D graphic 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 three-dimensional graphic display system for generating and displaying a three-dimensional graphic at a high speed from graphic positional information and third-dimensional information such as height.

[0002]

2. Description of the Related Art The invention according to Japanese Patent Application Laid-Open No. 61-148576 is to perform high-speed three-dimensional display on high-density information such as highly photographed image data. It calculates and stores accompanying information proportional to high-density information in order to achieve high speed. According to this method, when a ground surface approximated by a triangle is formed from high-density pixel information, high-speed display is performed by thinning out display target pixels when a plurality of pixels exist in the approximated triangle. Display is realized, and is not a high-speed display method for three-dimensional display from vector information.

When a vector graphic is displayed three-dimensionally, the value of the three-dimensional information such as altitude, temperature, and humidity attached to an arbitrary graphic or held independently of the graphic is used. Accordingly, a three-dimensional surface can be expressed by newly generating a surface forming the three-dimensional surface. The following method is known as a conventional technique of this type of three-dimensional display. In a map display processing device having map information and capable of calculating an elevation value at an arbitrary position, first, a grid-like information sequence is constituted by three-dimensional display at constituent points having plane position information from the viewpoint position / height. Create for the ground surface area and store the information in the frame memory. From the constituent points of the grid, a plane figure as a minimum display unit of the three-dimensional figure is created. Here, the plane figure has constituent point information and plane color information. Next, in the three-dimensional display, the elevation value is obtained for the constituent points of the grid.
Perspective transformation to the two-dimensional plane is performed on the constituent points having the three-dimensional information obtained here, and ridge lines are displayed and in-plane filling is performed on all the plane figures in accordance with the plane figure information, whereby the three-dimensional display is performed. Do. In the above method, the processing must be performed on an area other than the visual field, and since the interval between the constituent points of the grid is constant (equal interval method) irrespective of the distance from the viewpoint, the number of constituent points is different from the viewpoint. It is proportional to the square of the distance (see below). As a result, there is a problem that the calculation load becomes enormous as the three-dimensional display target area is enlarged.

FIG. 2 shows a conventional grid composing point, and
A method for displaying a dimension will be described. Generally, grid points 1 are created at regular intervals as shown in FIG. The configuration is as shown in FIG. When this is perspective-transformed, a perspective-transformed diagram 3 of the equally-spaced grid constituent points is displayed. In addition, 10 shows a viewpoint. In the case of this equal-interval method, the perspective of the displayed figure is clearly expressed, and it is easy to grasp the entire shape. However, when the three-dimensional display target area is wide, the number of grid points 1 is reduced. Rapidly becomes enormous, and the processing time becomes long. Also, when a figure having the same shape is perspective-transformed, a figure near the viewpoint is large, and a figure far from the viewpoint is displayed small, that is, a figure near the viewpoint is coarse, and a figure far away is densely represented. As a result, a method is conceivable in which the display density can be kept constant and the number of components can be suppressed. FIG. 3 shows a configuration example of a grid point according to this method. However, if this method is used as it is, the calculation for calculating the grid point 1 becomes complicated, and the figure after perspective transformation when the display density is constant loses perspective as shown in the perspective transformation diagram 5.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to realize high-speed processing in three-dimensional display when handling vector graphic information in view of the above-mentioned circumstances.

[0006]

In order to achieve the above object, plane position information and third information such as altitude, depth, temperature, humidity, etc., are set.
In generating and displaying a three-dimensional graphic from graphic data composed of dimensional information, means for inputting the position of the viewpoint, the height of the viewpoint and the direction of the viewpoint, means for determining the distance from the viewpoint, and the distance Means for determining a grid composing interval in accordance with the above, calculating a grid composing point position, a means for calculating a height for each of the calculated grid composing point positions, and 3 A three-dimensional graphic display system having means for generating a three-dimensional graphic and performing perspective transformation of the three-dimensional graphic into a two-dimensional plane and means for displaying the graphic is adopted.

[0007]

According to the present invention, the amount of calculation and the amount of display data can be reduced by judging the distance from the viewpoint, determining the grid configuration interval according to the distance, and calculating the grid configuration point position. The display can be speeded up. Also, when performing three-dimensional display, by increasing the interval between the constituent points of the figure with an increase in the distance from the viewpoint, the number of constituent surfaces of the figure is reduced, and the display can be speeded up. In addition, by partially changing the interval between the constituent points of the figure, it is possible to display a partial area in detail, and to increase the overall speed.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows an embodiment of the present invention, and shows a processing procedure for realizing high-speed three-dimensional display in a map display processing device which holds map information and can calculate an elevation value at an arbitrary position. First, respective information is input by means of inputting the position of the viewpoint, the height of the viewpoint, and the direction of the viewpoint (step 10).
1) A process for determining the distance D from the viewpoint is branched (step 102), and according to the distance,
That is, when the distance from the viewpoint D ≦ the lattice point interval change position D ₁ , the lattice constituent point interval is determined as d _1, and D ₁ <D ≦ D
_{In the case of 2} , it is determined as d _2, and similarly, in the case of Dn <D, it is determined as dn + 1, and the position is calculated by the means for calculating the lattice composing point position (step 103). Next, an elevation value is calculated by the height calculating means for each of the calculated positions of the grid points (step 104), and a three-dimensional figure is generated from the positions and heights of the grid points (step 104). 105) Transform the three-dimensional figure into a two-dimensional plane by means of perspective transformation to a two-dimensional plane (step 106), and display it on a screen or the like by means of graphic display (step 1).
07). With this processing procedure, map information is three-dimensionally displayed at high speed. The third dimension information includes altitude, depth, temperature, humidity, and the like.

FIG. 4 is a diagram showing the construction of grid points according to the present invention.
The method of three-dimensional display is shown. FIG. 4 shows a variable interval method, in which the grid point interval is increased according to the distance from the viewpoint 10. That is, when the trigger for increasing the grid point interval is a distance from the viewpoint, the trigger increases when a predetermined distance is reached. When the perspective transformation is performed on the basis of the grid composing points of the present method, the graphic is as shown in FIG. As described above, the variable interval method of the present invention reduces the number of constituent points and reduces the display density of planar graphics in an area located far away from the viewpoint, as compared with the conventional equal interval method shown in FIG. When a perspective transformation is performed, a plurality of plane figures are represented by a small number of pixels. As is clear from FIG. 4, even when the interval between the grid points is increased in accordance with the increase in the distance between the viewpoint and the display area, the graphic shape expressed on the display screen is not significantly affected.
However, an unnatural level difference occurs if this condition is maintained. For this step, as shown in FIG. 9, the auxiliary line 8 is drawn on the graphic plane after the perspective conversion. As a result, a display equivalent to that of the perspective transformation diagram 3 shown in FIG.

Here, a description will be given of a formula for calculating the amount of reduction in calculation when the variable interval method of the present invention is used. First, a comparison will be made between the conventional equal-interval method and the method of the present invention with respect to the number of points of the plane figure required to calculate the elevation value. In the case of the conventional equidistant method, the sum of the number of constituent points is N × (A + N−1) N: the number of grids in the horizontal method A: the number of constituent points in the front row, and as a result, the analytical display distance Ｎ N解析 Analysis display distance is ² . In the case of the method of the present invention, since the sum of the number of constituent points in a block having the same grid interval is constant even when the interval changes, P × BP: in a region where the grid interval is constant. B: The number of times the grid interval has been changed. As a result, since the analytical display distance Ｂ B, the total number of component points ∝ the analytical display distance. As described above, in the case of the conventional equal spacing method, the sum of the number of constituent points is proportional to the square of the analysis display distance, whereas in the method of the present invention, the sum of the number of constituent points is only proportional to the analysis display distance. Therefore, the number of constituent points is extremely small.

Next, an example of a position calculation formula for changing the grid point interval will be described with reference to FIGS. 5, 6, and 7. FIG. In FIG.
(In the figure, D _1, D ₂₎ lattice point interval change position D shows the relationship between the reference value of the horizontal grid point interval change d (in _{Fig, d 1, d 2, d} 3). As the distance from the viewpoint becomes farther (generally, D ₁ <D ₂ <... <Dm) and the grid interval is widened (generally, d ₁ <d ₂ <. Can be represented by However, in FIG. 5, the determinant of the change of the constituent point is limited to the distance from the viewpoint, but the change position may be changed depending on the size of the figure.

In FIG. 6, as an example, a terrain 15 is undulated, and the inclination of the figure is set to a maximum of 30 degrees.
An example in which a reference value d ′ for changing a grid point interval for an arbitrary topographic map when a reference value d for changing a grid point interval in the horizontal direction is set is shown. Reference numeral 11 denotes a screen, and 14 denotes a ground surface. The width of the reference value d for changing the grid point interval in the horizontal direction developed on the screen is dz, and the width developed on the screen is dz in order to obtain the same accuracy as a figure having an inclination. Should be the same, the reference value d ′ for changing the grid point interval is d ′ = d × cos (3
0 degree) = d / 2.

FIG. 7 derives an equation for determining the grid point interval change position D, where AB is the height corresponding to the grid point interval change reference value d 'on an arbitrary grid point interval change position D. Here is an example. First, a length A'B 'on the screen corresponding to the length AB between two points is obtained. For O'A 'and OA, O'A': OA = O "O ': O" O ∴ O'A' = (OA x O "O ') / O" O For “B” and OB, O′B ′: OB = O ″ O ′: O ″ O∴O′B ′ = (OB × O ″ O ′) / O ″ OA A′B ′ = O′A ′ + O′B ′ = (AB × O ″ O ′) / O ″ O (1) Total pixel amount Sw of screen 13 to be displayed, screen 11
When the pixel amount corresponding to A′B ′ is P and the height from the ground surface 14 is H, A′B ′ is converted into a pixel value from the relationship between the screen length and the pixel amount. : H = P: A′B′∴P = (Sw × A′B ′) / 2H (2) Here, the viewing angle is 45 degrees vertically (the angle between the line-of-sight center point 12 and the ground surface C of the screen 11). Assuming that the component point interval change distance D is the grid point interval reference value d with respect to the ground plane, O "O = DO" O '= O'C = HOA + OB = d * cos (30 degrees) = d / 2 By using this parameter, equation (1) can be arranged as follows: A′B ′ = (H × d / 2) / D = H × d / 2D When this result is substituted into equation (2), and D is solved, , P = (Sw / 2H) × (H × d / 2D) = Sw × d / 4D D = Sw × d / 4P Thus, the change position of the lattice point interval is determined from the viewpoint. It can be obtained as the grid point interval change distance D.

FIG. 8 shows an embodiment in which map data is superimposed on a three-dimensional display by applying the present invention. The display level change position of the map data (for example, road) to be superimposed on the three-dimensional figure is calculated by using the above-described method of calculating the grid point interval change position, and the position between each display level change position is close to the viewpoint. The display level is set so as to be lower as the distance from the viewpoint increases. On the other hand, the map data is given a display priority for each figure data, and is displayed only when the priority is lower than the above-mentioned display level. In the figure, there is a display screen in which the horizontal direction is the viewpoint direction with respect to the viewpoint position 10, where A is plane map data (road),
<1>, <2>, <
3> and <4> are display level change positions,.
And indicate a display level. The display priority was set to the display level up to the display level change position <3>, and lower than the display level change position <4>.
B is 3D after perspective map of plane map data (road) A
The dimension display map (road) is shown. Plan map data (road)
A , display level change positions <1>, <2>, <3> of map data (roads) superimposed and displayed on a three-dimensional figure.
And <4> are calculated using the above-described method of calculating the grid point interval change position, and the display level, and the distance between the display level change positions is lower as the position is closer to the viewpoint and farther from the viewpoint. Set to be higher. When such planar map data (road) A is perspective-transformed, a three-dimensional display map B as shown is displayed on the display screen. The map data (road) after the display level change position <4> in the plane map data (road) A is not displayed because the display priority is lower than the display level. In this way, by using the method of calculating the grid point interval change position, the data superimposed on the three-dimensional display can be reduced as the distance from the viewpoint position increases. It should be noted that the display level change position, the display level, and the display priority in the figure are merely examples, and it goes without saying that the respective calculated values and set values are determined by various conditions on the display of the map data.

FIG. 9 shows an embodiment in which the present invention is applied to reduce the interval between constituent points of a specific area. The specific area 16 is
This is a configuration example of a grid point 1 in this case. This is displayed using the method of calculating the grid point interval change position described above.
The position of the grid point 1 for generating the plane of the two-dimensional figure is obtained. Furthermore, the positions of the grid points are determined so that the interval between the constituent points is reduced with respect to the area required for detailed display preset in the graphic data or the like. Examples of the means for setting the area required for detailed display include a method of designating an area with predetermined graphic data or a method of determining the area based on the amount of change in the 3D information (when the 3D information is a height, The amount of change becomes the amount of change). As a result, the specific area can be displayed in detail, and graphic data to be displayed can be reduced as a whole.

FIG. 10 shows an embodiment in which the present invention is applied and three-dimensional display is performed using maps of different scales. In the figure,
1 represents 1 / 500,000, 2 represents 1 / 100,000, n represents 1 / 25,000 map data, and M represents a display device. These map data have different figure densities at the same position. The figure density for the same position is 1 / 500,000 <1 / 100,000 <1
/ 25,000. Thus, the display device M, 1 /
When displaying 25,000, 1 / 100,000 and 1 / 500,000 map data, the graphic display target scale change position is calculated in the same manner as the calculation of the lattice point interval change position. As shown in the figure, the map data having a smaller figure density is located farther away from each other at each of the calculated graphic display target scale change positions, and each map data is displayed. In this way, when displaying graphic data of a map of the same scale, a large amount of data must be processed if the distance from the viewpoint position is far away.
Using the calculated scale change position, automatically select the read destination of the graphic data to be displayed, and display the graphic from a scale with a coarse graphic data density per unit area in the distant place, so that high speed can be achieved. 3D display is possible. In addition, at a distant position, when a figure of the same density as that near the viewpoint is displayed, the figure is overwritten and displayed, and there is a problem that the shape of the figure cannot be determined. However, according to this method, Since the display data at a distant place is reduced, an effect is also obtained for the problem.

[0017]

As described in detail above, according to the present invention,
By reducing the amount of calculation and the amount of display data based on the two-dimensional vector graphic and the third-dimensional information, three-dimensional display can be speeded up. Also, the interval between the constituent points of the figure is
When three-dimensional display is performed, the number of graphics is increased with an increase in distance from the viewpoint, so that the number of constituent surfaces of the graphic is reduced, and display can be speeded up. Further, by partially changing the interval between the constituent points of the figure, it is possible to display the detail of a partial area, and to increase the speed as a whole.

[Brief description of the drawings]

FIG. 1 is a flowchart showing an embodiment of the present invention.

FIG. 2 is an explanatory view of an equal interval method.

FIG. 3 is an explanatory diagram of a constant density method.

FIG. 4 is an explanatory diagram of a variable interval system according to the present invention.

FIG. 5 is a diagram illustrating the relationship between grid point intervals and grid point interval change distances.

FIG. 6 is a diagram illustrating the relationship between the inclination of a figure and a reference value for changing grid point intervals in the horizontal direction.

FIG. 7 is an explanatory diagram of derivation of a grid point interval change position calculation formula.

FIG. 8 is an explanatory diagram of an embodiment of the present invention for superimposed display.

FIG. 9 is an explanatory diagram of an embodiment of the present invention for reducing the interval between constituent points of a specific area.

FIG. 10 is an explanatory diagram of an embodiment of the present invention using a different scale map.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Lattice point 2 Equidistant grid configuration diagram 3 Perspective transformation diagram by equidistant lattice configuration point 4 Constant spacing lattice configuration diagram 5 Perspective transformation diagram by fixed interval lattice configuration point 6 Variable spacing lattice configuration diagram 7 Perspective transformation by variable spacing lattice configuration point Figure 8 Auxiliary line 9 Perspective transformation diagram with auxiliary line 10 Viewpoint 11 Screen 12 Center line of sight 13 Display screen 14 Ground surface 15 Terrain 16 Specific area

Continuation of the front page (72) Inventor Yasue Nomoto 5-2-1 Omika-cho, Hitachi City, Ibaraki Prefecture Inside the Omika Plant, Hitachi, Ltd. (56) References JP-A-1-205277 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G06T 15/00-17/50

Claims (4)

(57) [Claims] 1. A display device capable of displaying graphic information on a display, wherein a three-dimensional graphic is generated from graphic data including plane position information and three-dimensional information such as altitude, depth, temperature, and humidity. When displaying, the position of the viewpoint,
Means for inputting the height of the viewpoint and the direction of the viewpoint, means for determining the distance from the viewpoint, means for determining the grid configuration interval according to the distance, means for calculating the grid configuration point position, Means for calculating the height for the position of the grid composing points, and generating a three-dimensional figure from the position and the height of the grid composing points,
A three-dimensional graphic display method, comprising: means for perspectively converting a three-dimensional graphic into a two-dimensional plane; and means for displaying a graphic. 2. The three-dimensional graphic display method according to claim 1, wherein the interval between constituent points of the three-dimensional graphic is larger than that of a graphic located at a distant position. 3. The method according to claim 1, wherein the interval between the constituent points of the three-dimensional display graphic of the specific area in the area for performing the three-dimensional display is reduced, and the intervals between the other constituent points are increased. 3D graphic display method. 4. A method according to claim 1, wherein when generating and displaying a three-dimensional graphic from a plurality of graphic data files having graphics of different densities, the file storing the graphic data to be displayed is separated by distance and distance. A three-dimensional graphic display method characterized by automatically selecting according to the angle of the line of sight.