JPH04167185A - Three-dimensional shape display method - Google Patents

Abstract

PURPOSE:To easily and freely perform shade and shadow processing on an object from a desired direction by attaching shade and shadow on the object by setting luminance on a curved surface comprising the object based on the direction of a light source. CONSTITUTION:Map information 12, 13 representing directions in three- dimensional shape in longitude and latitude are displayed on a display screen 5. A cursor 16 is displayed by superimposing on the map information 12, 13, and also, and the shade and shadow is attached on the object 10 by setting the luminance on the curved surface comprising the object 10 based on the directions of the light source in accordance with the longitude and latitude designated by the cursor 16. Thereby, it is possible to easily and freely perform the shade and shadow processing on the object 10 from the desired direction.

Description

[Detailed description of the invention] The present invention will be explained in the following order.

A: Industrial application field Summary of B invention C Conventional technology Problems that the invention attempts to solve EMeans for solving the problem (Figure 2).

F Effect (Fig. 2) G Example (Figs. 1 to 4) H Effect of the invention A Industrial application field The present invention relates to a three-dimensional shape display method, for example, CAD
(Cosputer aided design) This is suitable for application when adding shading to a three-dimensional object formed by a system.

B. Summary of the Invention The present invention provides a three-dimensional shape display method that displays map information representing a direction in a three-dimensional space in terms of longitude and latitude on a display screen, superimposes a cursor on this map information, and displays a cursor over the map information. By setting the brightness on the curved surface that makes up the object based on the direction of the light source according to the longitude and latitude specified in , shadows are added to the object.
To easily and freely perform shading processing on an object from a desired direction.

C. Conventional technology Conventionally, in CAD systems, objects with a three-dimensional shape designed by a designer are displayed with shading added to them, so that the objects are displayed as if they were captured by a video camera. Some designs have been developed to confirm the design effect.

In such a three-dimensional shape display method, each point on a curved surface in a three-dimensional space that defines the shape of an object is given a brightness as a parameter, and the point is assumed to exist at a predetermined position in the three-dimensional space and this curved surface. Depending on the relationship with the light source, the brightness is set to add shadows to the curved surface.

Assuming that the color and smoothness of the curved surface are constant, the brightness of this curved surface is determined by the amount of light from the light source, the distance between the light source and the object, and the angle formed by the light source and the object.

Normally, the light intensity of the light source is selected to be a constant value, and the distance between the light source and the object is selected to be infinite. In practice, the brightness of a curved surface depends on the angle formed by the light source and the object in three-dimensional space, that is, the direction of the light source. For example, there is a method disclosed in Japanese Unexamined Patent Application Publication No. 61-237171 for displaying a curved surface constituting an object by adding shading to it.

Problem to be Solved by the Invention However, when displaying an object having a three-dimensional shape by adding shading, the shading changes depending on the direction of the light source relative to the object, giving a different impression of the displayed object. , it is necessary to specify the optimal light source direction.

However, in the above-mentioned three-dimensional shape display method that performs shading processing, the direction of the light source when adding shading to an object is manually entered as a coordinate value in a three-dimensional space.

For this reason, it is difficult to predict what kind of shading will be added without looking at the object displayed after shading processing, and the user may fix the light source in a specific direction in three-dimensional space, or There was a problem that required numerical input of coordinate values representing the direction of the light source.

In addition, if you are not satisfied with the impression of an object displayed after shading processing, you have to enter the direction of the light source again numerically and perform shading processing, which requires a long processing time and ultimately reduces the usability of the object. It was still insufficient.

The present invention has been made in consideration of the above points, and it solves the conventional problems at once, and displays a three-dimensional shape that can easily and freely illuminate an object with a light source from a desired direction and perform shading processing. This is an attempt to propose a method.

E Means for Solving the Problems In order to solve the problems, in the present invention, an object 10 having a three-dimensional shape is displayed on the display screen 5, and a direction in a three-dimensional space centered on the object 10 is displayed. Map information 12.13 expressed in longitude and latitude is displayed, a cursor 16 is superimposed on the map information 12.13, and the direction of the light source that illuminates the object 10 is indicated on the map information 12.13 at the position of the cursor 16. The brightness on the curved surface constituting the object 10 is set according to the direction of the light source specified by the cursor 16, and the object 10 is shaded and displayed on the display screen 5. I decided to do so.

The direction of the light source in three-dimensional space is determined according to the longitude φ and latitude θ specified with the cursor 16 on the F-effect map information 12.13, and based on the direction of the light source, the direction on the curved surface constituting the object 10 is determined. By setting the brightness and adding shading to the object 10, it is possible to easily and freely perform shading processing on the object 10 from a desired direction.

G example An embodiment of the present invention will be described in detail below with reference to the drawings.

In FIG. 1, reference numeral 1 indicates a CAD system that executes the three-dimensional shape display method according to the present invention as a whole, and includes a three-dimensional shape display device 2 having a computer configuration including a central processing unit (CPU), and a display device for displaying images. 3 and a mouse 4 as a two-dimensional coordinate input device.

Three-dimensional shape data Do representing a three-dimensional object generated by a three-dimensional shape generating device (not shown) is input to the three-dimensional shape display device 2, and is sent to the display device 3 as display data D1. , an object 10 having a three-dimensional shape is displayed on a display screen 5 of a display device 3 shown in FIG.

Furthermore, when the user uses the mouse 4 to specify "shading processing J6A" on the menu icon 6 of the display screen 5, the CPU of the three-dimensional shape display device 2 executes the three-dimensional shape display program RTO shown in FIG. Run and display screen 5
A shading is added to the three-dimensional object 1O projected in the image according to the direction of the light source input.

That is, the CPU of the three-dimensional shape display device 2 enters the three-dimensional shape display program RTO, and first displays the work menu 11 in a window on the right side of the display screen 5 in step SPI.

This work menu 11 includes graphic information for setting and inputting the direction of the light source when adding shadows to the object 10.
Map information 12 in a world coordinate system centered on an object 10 in three-dimensional space, map information 13 in a screen coordinate system, a sphere 14 in a world coordinate system, a sphere 15 in a screen coordinate system, and a cursor 16 are displayed.

In reality, when projecting an object 10 having a three-dimensional shape on the display screen 5 which is a two-dimensional plane, a right-handed XYZ coordinate system (so-called world coordinate system) representing the three-dimensional space in which the object 10 is defined is used. , it is known that a left-handed UVW coordinate system (so-called screen coordinate system) representing the secondary forward plane onto which the object 10 is projected is required.

In the case of this example, a celestial sphere is assumed in which the object 10 is placed at the center of the world coordinate system and the screen coordinate system, respectively, and the direction of this celestial sphere in three-dimensional space is expressed as longitude and latitude using the conformal cylindrical projection (Mercator projection). The map information 12 and 13 obtained are displayed on the display screen 5.

Map information 1 of this world coordinate system and screen coordinate system
2 and 13, the horizontal axis is 0° from the left as shown in Figure 4.
The longitude is ~360°, and the vertical axis is centered at Q II,
It is formed using the Mercator projection, which has latitudes with the upper end at +90'' and the lower end at 190°.

In fact, for example, in the map information 12 of the world coordinate system, latitude 0° and longitude 0° are assumed to be the transverse direction of the X axis, and latitude 0° and longitude 90° are assumed to be the transverse direction of the Y axis.

A cursor 16 is displayed superimposed on the world coordinate system map information 12, and a desired position on the map can be specified and input using the cursor 16. As shown in the figure, the cursor 16 is, for example, a cross cursor, and vertical lines and horizontal lines are displayed parallel to meridian lines and latitude lines, respectively, so that the position can be specified accurately.

Next, the CPU of the three-dimensional shape display device 2 executes step SP2.
, the light source whose position is to be specified and the light intensity of that light source are entered.

That is, in the case of this embodiment, although not displayed on the work menu 11, a plurality of light sources can be irradiated onto the object 10, and the user uses the mouse 4 to specify the light source and its position. If you input the light intensity of the light source, C
The PU moves to the next step SP3.

In this step SP3, the user operates the mouse 4 to change the direction of the light source to, for example, map information 1 in the world coordinate system.
2 with the cursor 16 and the trigger button is turned on, the X-Y coordinates representing the position of the cursor 16 at this time are input to the three-dimensional shape display device 2.

Next, the CPU of the three-dimensional shape display device 2 executes step 7'SP.
Move to step 4 and place star marker 7 at the specified cursor position.
After displaying A, the CPU converts the X-Y coordinates of the cursor position into longitude and latitude on the map information 12 in step SP5.

Here, the position of the cursor 16 is input as X-Y coordinates on the screen, and is converted into longitude and latitude using a conversion table within the three-dimensional shape display device 2.

In practice, this conversion table is as follows, where r is the radius of the celestial sphere: π r (φ: longitude, d: distance from longitude 0°) π r (θ: latitude, L: distance from latitude 0°) The Mercator projection conversion formula expressed as is used.

Therefore, as shown in FIG. 4, by inputting the values of the X-Y coordinates specified by the cursor 16 as distances d and L from longitude 0° and latitude O°, longitude φ and latitude θ can be obtained. can.

The longitude φ and latitude θ of the world coordinate system obtained in this way are the world coordinates/
Using a screen coordinate conversion table (not shown), the coordinates are converted into longitude and latitude in the screen coordinate system for display on the display screen 5.

Next, the CPU of the three-dimensional shape display device 2 executes step SP6.
Then, three-dimensional coordinates XYZ corresponding to the position designated by the cursor 16 are determined based on the determined longitude φ and latitude θ.

Note that when determining the three-dimensional coordinates XYZ from the longitude φ and the latitude θ, the coordinate value Z can first be determined using the latitude θ of equation (2) as shown in the following equation, π r .

Letting the radius of the cross section of the celestial sphere at this coordinate value Z be R, this radius R is calculated by the following formula, R= r cos θ −−−−−・
It can be expressed as (4), and this radius R is also the maximum value that the coordinate values X and Y can take in the coordinate value Z.

Using this radius R and the longitude φ in equation (1), the coordinate value
and Y is the following formula, X=-Rcos φ (5
)Y=-Rsinφ-old- It can be obtained as in (6).

After this, the CPU of the three-dimensional shape display device 2 performs step SP7.
, the three-dimensional coordinates XYZ obtained as described above
Using the fact that corresponds to a three-dimensional direction vector,
In this direction, a bright spot 8A is placed on the sphere 14 representing the world coordinate system.
Display as .

Here, the sphere 14 representing the world coordinate system is formed in a spherical shape centered on the intersection of the XYZ axes, and similarly the sphere 15 representing the screen coordinate system is formed in a spherical shape centered on the intersection of the U and W axes. It is formed.

In this embodiment, a sphere 14 representing the world coordinate system
In addition, the direction of the light source specified on the world coordinate system map information 12 is displayed as a bright spot 8A, so that the direction of the light source specified by the user can be easily confirmed.

The surfaces of these spheres 14 and 15 are formed of minute mesh,
Displayed as if it were a translucent sphere, the coordinate axes passing through the center can be easily seen, and the back sides of the spheres 14 and 15 (
Even when the light source moves from 0° to 90° and from 270° to 360° longitude, the direction of the light source can be visually observed.

Furthermore, cylindrical models 9A and 9B are displayed inside the spheres 14 and 15, and shading is added to the cylindrical models 9A and 9B according to the light source from the specified direction. This makes it easy to understand the irradiation status.

In addition to this, at the center of these spheres 14 and 15,
The XYZ axes and UVW axes are displayed in red, green, and blue, respectively, and the colors of the spheres 14 and 15 themselves change stepwise for every ⅛ sphere.

In addition, in the case of this embodiment, the above-mentioned map information 12 and 13
The celestial sphere is also displayed in such a way that the color tone changes stepwise according to the position of the celestial sphere, so that the user can easily understand the position of the celestial sphere as a whole.

Next, the CPU of the three-dimensional shape display device 2 moves to step SP8, and the three-dimensional shape object 10 projected on the display screen 5 of the display device 3 is shaded by irradiating the light source from the specified direction. The process is started, and as a result, the object 0 that has been subjected to the shading process is displayed on the display screen 5.

Subsequently, the CPU of the three-dimensional shape display device 2 moves to step SP9 and waits for the user to judge the shading processing result. For example, if the user uses the mouse 4 to point to the area rQUITJ6B indicating termination on the menu icon, , the CPU moves to step 5P10 and ends the three-dimensional shape display program RTO.

Further, in this step SP9, if the user instructs to continue the process using the mouse 4, for example, the CPU moves to step SP9.
Step 5P3-3P4-3P5-3P6-
3P7 to 3P8 are executed, and the direction of the light source is again specified and the shading process using the light source in the specified direction is performed.

Note that in the three-dimensional shape display program RTO described above, the user specifies the direction of the light source on the map information 12 of the world coordinate system, but the direction of the light source is specified on the map information 1 of the screen coordinate system.
Even if you specify above 3, it will be processed in the same way, and at this time cursor 1
Map information 13 in the screen coordinate system according to the position specification in 6
A marker 7B is displayed above, and a bright spot 8B corresponding to the direction of the light source specified on the sphere 15 of the screen coordinate system is displayed.

Therefore, the user can specify the direction of the light source in an easy-to-use coordinate system among the map information 12 or 13 of the world coordinate system or the screen coordinate system, and the usability for the user can be improved.

In the above method, for example, if the user moves the cursor 16 to specify one point on the upper end of the map information system 2 of the world coordinate system, the Z-axis stop direction, that is, the north pole of the celestial sphere, is specified due to the properties of the Mercator projection. That means that.

Generally, this is the direction directly above when viewed from the object 10, and in the world coordinate system, a light source can be specified from a fixed direction with respect to the object IO.

On the other hand, when specifying a light source using the map information 13 in the screen coordinate system, it is possible to specify a light source from a fixed direction with respect to the screen.

In other words, if you specify the light source in the world coordinate system, even if the light source is directly above the object 10, if you change the viewpoint position, it will no longer be directly above the object 10, whereas if you specify the light source in the screen coordinate system, the light source will not be directly above the object 10. Even if you change the position, the light source remains directly above you.

In other words, once you specify the light source in the world coordinate system,
Even if the viewpoint position is changed, the shadow on the object 10 remains unchanged, whereas if the light source is specified in the screen coordinate system, the direction of the light source toward the object 10 changes according to the change in the viewpoint position, and the shadow appears unchanged. is displayed differently.

Therefore, for example, if it is desired to always illuminate the light source from the front of the display screen 5 (that is, from the user side), it is sufficient to specify a position of latitude 0° and longitude 180° in the map information 13 of the screen coordinate system.

For example, if it is desired to always illuminate the object 10 with the light source from above, it is sufficient to specify one point at the upper end of the map information 12 in the world coordinate system as described above.

According to the above method, the map information 12 and 13 representing the direction in the three-dimensional space in terms of longitude and latitude are displayed on the display screen 5, the cursor 16 is superimposed on the map information 12 and 13, and the cursor 16 is By setting the brightness on the curved surface constituting the object 10 based on the direction of the light source according to the longitude and latitude specified in step 16, and adding shadows to the object 10, it is possible to easily and freely adjust the object 10. A three-dimensional shape display method that can perform shading processing from a desired direction can be realized.

Furthermore, according to the above method, the map information 12 and 13 of the world coordinate system and the screen coordinate system are prepared, and by making it possible to specify the direction of the light source with respect to the object 10 using either of them, it is possible to specify the direction of the light source with respect to the object 10 depending on the purpose of shading processing. It is possible to use different coordinate systems, thereby realizing a three-dimensional shape display method that can significantly improve usability for the user.

Further, according to the above method, the sphere 14 corresponding to the map information 12 and 13 in the world coordinate system and the screen coordinate system
and 15 are displayed, and the direction of the light source specified on the spheres 14 and 15 is displayed with bright spots 8A and 8B, and shading processing is also performed on the cylindrical models 9A and 9B displayed in the spheres 14 and 15. As a result, even when the object 10 has a complicated shape, it is possible to easily understand the direction of the light source and the effect of shading processing, and thus the three-dimensional shape display method can further improve usability for the user. can be realized.

In the above-described embodiment, the direction of the light source is specified using map information of the world coordinate system and the screen coordinate system, but the present invention is not limited to this, and the present invention is not limited to this. The direction of the light source may also be specified by

Furthermore, in the above embodiment, when specifying the direction of the light source on the map information of the world coordinate system or the screen coordinate system, markers and bright spots are displayed on the map information of the world coordinate system or the screen coordinate system and on the celestial sphere, respectively. However, the present invention is not limited to this, and markers and bright spots may also be displayed on the map information and the celestial sphere in the screen coordinate system or the world coordinate system, respectively.

Furthermore, in the above embodiment, a case was described in which the celestial sphere was expressed using the Mercator projection as map information.
The same effects as those of the above-mentioned embodiments can be achieved even if various projection projection methods are used.

Further, in the above-described embodiment, a case was described in which two-dimensional coordinates were input using a mouse, but the present invention is not limited to this, and various two-dimensional coordinate input devices may be used.

Furthermore, in the above-described embodiment, the present invention is applied to the case where shading is performed on a three-dimensional object in a CAD system, but the present invention is not limited to this, for example, when shading is performed in a computer graphics system, etc. It is also widely applicable and suitable.

H Effects of the Invention As described above, according to the present invention, map information representing the direction of an object in three-dimensional space in terms of longitude and latitude is displayed, and the direction of the light source is specified on the map information. It is possible to realize a three-dimensional shape display method that can easily and freely perform shading processing on an object from a desired direction.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a CAD system that executes an embodiment of the three-dimensional shape display method according to the present invention, FIG. 2 is a route map for explaining the display screen, and FIG. FIG. 4 is a flowchart for explanation and a route map for explanation of map information. 1...CAD system, 2...three-dimensional shape display device, 3...display device, 4.
...Mouse, 5...Display screen, 6...
...Cursor, 7...Marker, 8...
・Bright spot, 9... Cylinder model, 10...
Object, 11... Work menu, 12.13...
...Map information, 14.15...Celestial sphere.

Claims (1)

[Claims] Displaying an object having a three-dimensional shape on a display screen,
Display map information representing the direction in a three-dimensional space centered on the object in longitude and latitude, display a cursor superimposed on the map information, and determine the direction of the light source that illuminates the object at the position of the cursor. Specify the above longitude and latitude on the above map information, set the brightness on the curved surface that constitutes the above object according to the direction of the above light source specified with the above cursor, add shading to the above object, and display the above. A three-dimensional shape display method characterized by displaying on a screen.