JP3063144B2 - 3D shape display method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described in the following order.

A Industrial field B Outline of the invention C Conventional technology D Problems to be solved by the invention E Means for solving the problem (FIG. 2) F operation (FIG. 2) G embodiment (FIGS. 1 to 4) The present invention relates to a method for displaying a three-dimensional shape, for example, a CAD (com).
This is suitable for applying a shadow to a three-dimensional object formed by a puter aided design system.

B. Summary of the Invention In the three-dimensional shape display method, the present invention displays map information indicating a direction in a three-dimensional space by longitude and latitude on a display screen, and superimposes and displays a cursor on the map information. Based on the direction of the light source corresponding to the longitude and latitude specified in, the brightness on the curved surface constituting the object is set to add a shadow to the object, so that the object can be easily and freely desired. Can be shaded.

C Conventional technology Conventionally, in a CAD system, a shading is added to an object having a three-dimensional shape designed by a designer and displayed, so that it is displayed as if a real object is photographed with a video camera. Some are designed to confirm the design effect.

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

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

Normally, the light amount 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 infinity.In practice, the brightness of the curved surface is the angle between the light source and the object in the three-dimensional space,
That is, there is a method disclosed in JP-A-61-237171, which is determined by the direction of the light source, and for example, a method for displaying a curved surface constituting an object with shading added thereto.

D Problems to be Solved by the Invention By the way, when an object having a three-dimensional shape is displayed with a shadow added thereto, the impression of the displayed object is changed according to the direction of the light source with respect to the object. Because they are different, it is necessary to specify the optimal light source direction.

However, in the three-dimensional shape display method for performing the above-described shadow processing, a direction of a light source when a shadow is added to an object is numerically input as, for example, a coordinate value in a three-dimensional space.

Is what shade because this is added, it is difficult to predict if viewed object displayed are shading, Users can fix the light source in a specific direction in three-dimensional space, vague There is a problem that the coordinate value representing the direction of the light source has to be input numerically.

In addition, if the impression of the object displayed by the shadow processing is not satisfactory, it is necessary to input the numerical value of the direction of the light source again to perform the shadow processing, and a long processing time is required. It was still insufficient.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above points, and provides a three-dimensional shape display method capable of easily and freely irradiating an object with a light source from a desired direction to perform shading processing by solving the conventional problems at once. It is intended to propose.

Means for Solving Problem E In order to solve the problem, in the present invention, an object 10 having a three-dimensional shape is displayed on the display screen 5 and a direction in the three-dimensional space around the object 10 is changed. Display map information 12 and 13 represented by longitude and latitude,
A cursor 16 is superimposed on 13 and the direction of the light source that irradiates the object 10 at the position of the cursor 16 is specified by the longitude φ and the latitude θ on the map information 12 and 13. The brightness on the curved surface constituting the object 10 is set according to the direction, and a shadow is added to the object 10 so that the object 10 is displayed on the display screen 5.

F action The direction of the light source in the three-dimensional space is obtained in accordance with the longitude φ and the latitude θ designated by the cursor 16 on the map information 12 and 13, and based on the direction of the light source, the direction of the curved surface constituting the object 10 is determined. By setting the brightness to add a shadow to the object 10, the shadow processing can be easily and freely performed on the object 10 from a desired direction.

G Example Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

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

The three-dimensional shape display device 2 receives three-dimensional shape data D0 representing a three-dimensional shape object generated by a three-dimensional shape generation device (not shown), and sends it to the display device 3 as display data D1. An object 10 having a three-dimensional shape is projected on the display screen 5 of the display device 3 shown in FIG.

When the user designates “shadow processing” 6A on the menu icon 6 on the display screen 5 using the mouse 4, for example, the CPU of the three-dimensional shape display device 2 displays the three-dimensional shape display program RT0 shown in FIG. To add a shadow corresponding to the direction of the light source set and input to the three-dimensional object 10 projected on the display screen 5.

That is, the CPU of the three-dimensional shape display device 2 enters the three-dimensional shape display program RT0, and first displays a work menu 11 on the right side of the display screen 5 in step SP1.

The work menu 11 includes map information 12 in the world coordinate system centered on the object 10 in a three-dimensional space, System map information 13, sphere 14 in world coordinate system, sphere 15 in screen coordinate system, and cursor 16
Is projected.

When an object 10 having a three-dimensional shape is actually projected on the display screen 5 formed of a two-dimensional plane, a right-handed XYZ coordinate system (so-called world coordinate system) representing a 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 a two-dimensional plane on which the object 10 is projected is required.

In the case of this embodiment, a celestial sphere in which the object 10 is arranged at the center of the world coordinate system and the screen coordinate system is assumed, and the direction of the celestial sphere in the three-dimensional space is determined by longitude and latitude using a conformal cylindrical projection (Mercator projection). Are displayed on the display screen 5.

Map information of this world coordinate system and screen coordinate system
12 and 13, the horizontal axis is 0 ° to
The longitude is 360 °, the vertical axis is 0 ° at the center, and the upper end is +9
It is formed by Mercator projection with latitudes of 0 ° and a lower end of −90 °.

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

A cursor 16 is superimposed on the map information 12 in the world coordinate system, and a desired position on the map can be designated and input by the cursor 16. As the cursor 16, for example, a crosshair cursor is used as shown in the figure, and a vertical line and a horizontal line are displayed in parallel with the meridian and the latitude line, respectively, so that the position can be specified accurately.

Subsequently, the CPU of the three-dimensional shape display device 2 proceeds to step SP2, and has a light source for specifying a position and a setting input of the light amount of the light source.

That is, in the case of this embodiment, although not displayed on the work menu 11, the object 10 can be irradiated with a plurality of light sources. If you set and input the light amount of the light source, the CPU
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 12 in the world coordinate system.
When the cursor 16 is pointed upward and the trigger button is turned on, the XY coordinates representing the position of the cursor 16 at this time are input to the three-dimensional shape display device 2.

Subsequently, the CPU of the three-dimensional shape display device 2 proceeds to step SP4 to display the star-shaped marker 7A at the designated cursor position, and then, at step SP5, the CPU displays the XY coordinates of the cursor position in the map information 12. Convert to above longitude and latitude.

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

In practice, this conversion table is given by the following equation, where the radius of the celestial sphere is r. The conversion formula of the Mercator projection represented by is used.

Therefore, as shown in FIG. 4, if the values of the XY coordinates designated by the cursor 16 are input as the distances d and L from the longitude 0 ° and the latitude 0 °, the longitude φ and the latitude θ can be obtained. Can be.

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

Subsequently, the CPU of the three-dimensional shape display device 2 proceeds to step SP6, where the cursor is set based on the obtained longitude φ and latitude θ.
The three-dimensional coordinates XYZ corresponding to the position specified by 16 are obtained.

When the three-dimensional coordinates XYZ are obtained from the longitude φ and the latitude θ, first, the coordinate value Z is calculated using the latitude θ of the equation (2) as follows: Can be obtained as follows.

Assuming that the radius of the circle of the cross section of the celestial sphere at the coordinate value Z is R, the radius R can be represented by the following equation: R = r cos θ (4), and the radius R is the coordinate value Z Are the maximum values that the coordinate values X and Y can take.

Using the radius R and the longitude φ of the equation (1), the coordinate values X and Y are expressed by the following equation: X = −R cos φ (5) Y = −R sin φ (6) You can ask.

Thereafter, in step SP7, the CPU of the three-dimensional shape display device 2 uses the fact that the three-dimensional coordinates XYZ obtained as described above correspond to the three-dimensional direction vector to represent this direction in the world coordinate system. It is displayed on the sphere 14 as a bright spot 8A.

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 UVW axes. ing.

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

The surfaces of the spheres 14 and 15 are formed of fine meshes, are displayed as if they are semi-transparent spheres, and the coordinate axes passing through the center can be easily viewed.
Even when the light source moves between (゜ -90 ° and 270 ° -360 °), the direction of the light source can be viewed.

Also inside the spheres 14 and 15 are the cylindrical models 9A and 9B
Is displayed, and a shade corresponding to the light source from the designated direction is added to the cylinder models 9A and 9B, so that the user can easily grasp the illumination state of the light source.

In addition to this, at the center of the spheres 14 and 15, the XYZ axis and the UVW axis are displayed in red, green, and blue, respectively, and the spheres 14 and 15 themselves also have a color tone every 1/8 sphere. It is made to change step by step.

Further, in the case of this embodiment, the above-mentioned map information 12 and 13 are also displayed such 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. ing.

Next, the CPU of the three-dimensional shape display device 2 proceeds to step SP8, where the three-dimensional shape object 10 projected on the display screen 5 of the display device 3 is shaded so as to emit a light source from a designated direction. The processing is started, and as a result, the object 10 subjected to the shading processing is displayed on the display screen 5.

Subsequently, the CPU of the three-dimensional shape display device 2 proceeds to step S
Going to P9, wait for the user to judge the shading processing result,
For example, when the user designates the area of “QUIT” 6B indicating the end on the menu icon by using the mouse 4, the CPU proceeds to step SP10 to execute the three-dimensional shape display program RT0.
To end.

In this step SP9, for example, when the user instructs continuation of the processing using the mouse 4, the CPU executes steps SP3-SP4-SP5-SP6-SP7-SP8 over step SP2.
The designation input of the direction of the light source and the shading process by the light source in the designated direction are performed again.

In the above-described three-dimensional shape display program RT0, the user specifies the direction of the light source on the map information 12 in the world coordinate system, but the same processing is performed even if the direction of the light source is specified on the map information 13 in the screen coordinate system. At this time, the marker 7B is displayed on the map information 13 in the screen coordinate system according to the position designation of the cursor 16, and the luminescent spot 8B according to the direction of the light source designated on the sphere 15 in the screen coordinate system is displayed. Is done.

Therefore, the user can specify the direction of the light source in a coordinate system that is easy to use, out of the map information 12 or 13 in the world coordinate system or the screen coordinate system, thereby improving the usability of the user.

In the above method, for example, if the user moves the cursor 16 and designates one point at the upper end on the map information 12 in the world coordinate system, the Z-axis positive direction, that is, the north pole of the celestial sphere is designated according to the characteristics of the Mercator projection. It was done.

This is generally a direction directly above the object 10, and a light source from a fixed direction can be specified for the object 10 in the world coordinate system.

On the other hand, when the light source is specified by the map information 13 in the screen coordinate system, the light source can be specified from a fixed direction with respect to the screen.

That is, if you specify the light source in the world coordinate system,
Even if the light source is directly above the object 10, if the viewpoint position is changed, the light source will not be directly above. On the other hand, if the light source is specified in the screen coordinate system, the light source will be directly above even if the viewpoint position is changed.

In other words, once the light source is specified in the world coordinate system, the shading on the object 10 is displayed without change even if the viewpoint position is changed, whereas if the light source is specified in the screen coordinate system, As a result, the direction of the light source to the object 10 changes, and the shadow changes.

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

Further, for example, when it is desired to always illuminate the light source from above the object 10, one point at the upper end of the map information 12 in the world coordinate system may be specified as described above.

According to the above-described method, map information 12 and 13 representing directions in a three-dimensional space by longitude and latitude are displayed on the display screen 5, and the cursor 16 is superimposed on the map information 12 and 13, and the cursor information is displayed. Based on the direction of the light source corresponding to the longitude and latitude specified in 16, the brightness on the curved surface constituting the object 10 is set to add a shadow to the object 10, so that the object 10 can be easily and freely set. A three-dimensional shape display method capable of performing shading processing from a desired direction.

Further, according to the above-described method, map information 12 and 13 in the world coordinate system and the screen coordinate system are prepared, and the direction of the light source with respect to the object 10 can be designated by either of them. Thus, a coordinate system to be designated can be properly used, and a three-dimensional shape display method can be realized which can significantly improve the user's convenience.

Further, according to the above-described method, the sphere 14 and the sphere 14 corresponding to the map information 12 and 13 in the world coordinate system and the screen coordinate system.
15 is displayed, and the direction of the light source specified on the spheres 14 and 15 is displayed as bright spots 8A and 8B, and the shadow processing is also performed on the cylindrical models 9A and 9B displayed in the spheres 14 and 15. Thereby, even when the object 10 has a complicated shape,
The direction of the light source and the effect of the shading process can be easily grasped, and a three-dimensional shape display method that can further improve the usability of the user can be realized.

In the above-described embodiment, the case where the direction of the light source is designated using the map information of the world coordinate system and the screen coordinate system has been described. However, the present invention is not limited to this, and any one of the map information may be used. Alternatively, the direction of the light source may be designated.

Further, in the above-described embodiment, when the direction of the light source is specified on the map information of the world coordinate system or the screen coordinate system, the marker and the bright spot are displayed on the map information of the world coordinate system or the screen coordinate system and the celestial sphere, respectively. However, the present invention is not limited to this, and a marker and a bright point may be displayed on the map information in the screen coordinate system or the world coordinate system and also on the celestial sphere.

Further, in the above-described embodiment, the case where the celestial sphere is represented by the Mercator projection as the map information has been described. However, the present invention is not limited to this, and the same effect as in the above-described embodiment can be obtained by using various projection projections. realizable.

Furthermore, in the above-described embodiment, a case has been described in which two-dimensional coordinates are input using a mouse. However, 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 shadow processing is performed on a three-dimensional object in a CAD system.However, the present invention is not limited to this. For example, when shadow processing is performed in a computer graphic system. It is also suitable for wide application to the like.

H Effect of the Invention As described above, according to the present invention, by displaying map information representing the direction of an object in three-dimensional space by longitude and latitude, and by specifying the direction of the light source on the map information, A three-dimensional shape display method capable of easily and freely shading an object from a desired direction can be realized.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a CAD system for executing an embodiment of a three-dimensional shape display method according to the present invention, FIG. 2 is a schematic diagram for explaining a display screen thereof, and FIG. FIG. 4 is a schematic diagram for explaining map information. 1 ... CAD system, 2 ... 3D shape display device, 3 ...
… Display device, 4 …… mouse, 5 …… display screen,
6 ... Cursor, 7 ... Marker, 8 ... Bright point, 9 ... Cylinder model, 10 ... Object, 11 ... Work menu, 12, 13 ...
... Map information, 14, 15 ... Spherical sphere.

Claims (1)

(57) [Claims] An object having a three-dimensional shape is displayed on a display screen, and map information indicating a direction in a three-dimensional space centered on the object by longitude and latitude is displayed, and a cursor is displayed on the map information. Is superimposed, and the direction of the light source that irradiates the object at the position of the cursor is specified by the longitude and latitude on the map information. According to the direction of the light source specified by the cursor, the object is displayed. A three-dimensional shape display method, comprising: setting a luminance on a curved surface to be formed; adding a shadow to the object; and displaying the object on the display screen.