JPH07129795A - Computer graphics system with function of changing image lighting effect - Google Patents

Abstract

(57) [Summary] [Purpose] The lighting effect of the displayed image can be changed easily. [Structure] An input unit 105 for directly setting a lighting position such as a highlight position in a display image and brightness of the highlight position, and a corresponding storage unit 303 for obtaining a condition of a light source satisfying a set lighting request command. A light source condition determining unit 307 for rewriting the light source data is provided. This means 307
In order to satisfy the requirements such as the highlight position and brightness input by the above, the shading equation is inversely solved to obtain conditions such as the direction, position, and brightness of the light source, and the corresponding storage unit 30 is obtained.
Rewrite the light source data of 3. The image generating means 304 generates a two-dimensional image based on the rewritten light source data. This allows the user to easily adjust the image having the desired lighting effect.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to computer graphics systems, and more particularly to image generation including adjusting lighting effects on a three-dimensional object when displaying the object in a two-dimensional image.

[0002]

2. Description of the Related Art Conventionally, when generating an image of a three-dimensional scene in a computer graphics system, first, a user inputs shape data, light source data, viewpoint data, etc. of a display object into a computer, and the computer receives the input data. A display image of the object is generated based on the above and displayed on the screen. Here, the shape data is data representing the shape of an object or the like to be displayed, and the light source data refers to data such as the direction, position, and brightness of a light source that illuminates the object in order to add an illumination effect to the image to be displayed. The viewpoint data is data that specifies the direction, position, etc. of the viewpoint of a person or a camera viewing the object.

When the user wants to change the illumination effect of the display image for the image generated in this way, the user can change the arrangement of the light source and the surface attribute of the object through the input means while looking at the image displayed on the screen. By changing it, a display image having a desired lighting effect is generated.

[0004]

However, according to the above-mentioned conventional technique, in the operation of changing the lighting effect, for example, the lighting position such as the highlight position of the object whose brightness is desired to be the strongest and the brightness thereof are predicted. However, since it is necessary to change the position of the light source by three-dimensional coordinate input and set the brightness, there is a problem that the operation for obtaining a desired lighting effect is complicated.

An object of the present invention is to provide a computer graphics system capable of easily changing the lighting effect of a displayed image.

[0006]

In order to achieve the above object, the present invention sets shape data representing the shape of an object to be displayed and viewpoint conditions of a display image such as a position and a direction at which the object is viewed. Storage means for storing viewpoint data and light source data for setting a condition of a light source for giving a lighting effect to a display image of the object, and an object based on the shape data, the viewpoint data and the light source data stored in the storage means. In a computer graphics system including an image generation unit that generates a display image and a display unit that displays the display image generated by the image generation unit, a lighting request command for directly setting a lighting effect in the display image is input. Input means and light source condition determination for rewriting the light source data of the corresponding storage unit by obtaining the condition of the light source that satisfies the illumination request command input from this input means Characterized in that a stage.

If the object has a three-dimensional shape, the image generating means converts the three-dimensional shape into a two-dimensional image and generates it.

The illumination request command includes a command for designating an arbitrary point as a highlight position for setting the brightness of the surface of the object of the display image (surface brightness of the object), and the light source condition when the command is input. The determining means adjusts the position of the light source according to the highlight position. Further, it is characterized in that it includes a command for designating the value of the surface brightness, and in that case the light source condition determining means adjusts the brightness of the light source or the distance between the light source and the object.

[0009]

By providing such means, according to the present invention, the above object can be achieved by the following operation.

Generally, in a computer graphics system, a three-dimensional shape with a lighting effect is converted into a two-dimensional image based on shape data, viewpoint data, and light source data by a calculation formula called a shading equation described later. Convert. The light source condition determining means of the present invention rewrites the light source data by solving the shading equation in reverse. That is, the user can directly set the lighting effect in the display image, for example, the highlight position, the brightness of the highlight position, etc., via the input unit, and the function of the light source condition determining unit satisfies the set lighting effect. The conditions such as the direction, position, and brightness of the light source are obtained, and the light source data in the corresponding storage unit is rewritten. The image generating means generates a two-dimensional image based on the rewritten light source data. As a result, the lighting effect of the image can be easily adjusted to that desired by the user.

That is, according to the shading equation,
When the light source is located in the direction opposite to the direction of the line of sight with respect to the normal direction of the object surface at an arbitrary position, the brightness at that position becomes the strongest. Therefore, for example, when a highlight position is designated, the light source condition determining means searches the shape data of the portion displayed at the highlight position and finds the normal vector of the shape of that point. Next, according to the three-dimensional coordinate system, a direction vector in the viewpoint direction is obtained from the designated highlight position. Then, the position of the light source is set in a direction opposite to the line-of-sight direction with respect to the normal vector. By generating an image again based on the light source data changed in this way, the brightness at the designated highlight position can be maximized.

Further, the brightness of the light source can be obtained by solving the shading equation based on the brightness of the surface of the shape.

[0013]

EXAMPLES The present invention will be described below based on examples.
FIG. 1 shows a system configuration diagram of a computer graphic system according to an embodiment of the present invention. Broadly speaking, a central processing unit 10 that controls and calculates the processing of this system.
1, a data storage device 103 for storing various data related to processing, a display device 104 for displaying an image of a processing result and necessary information on a screen, and an input device 105 such as a mouse or a keyboard for inputting a user's instruction. It is configured to include.

The central processing unit 101 includes an image generation unit 304,
The image display unit 305, the shape selection / normal vector calculation unit 306, the light source condition determination unit 307, and the input control unit 308 are included. The image generation unit 304 generates a two-dimensional image from the shape data, the viewpoint data, and the light source data. Image display unit 30
Reference numeral 5 controls to display the generated image on the display device 104. The shape selection / normal line calculation unit 306 is used by the input control unit 30.
Based on an instruction input via 8, the shape data of the object corresponding to the pointing point on the screen pointed by the cursor or the like is searched from the data storage device 103, and the normal line of the shape at the point position is calculated. The light source condition determining unit 307
The optimum light source condition is calculated from the calculation condition of the illumination calculation, the shape data of the object corresponding to the designated point on the screen, the normal data obtained by the shape selection / normal calculation unit 306, and the viewpoint data. The input control unit 308 interprets commands and instructions input from the input device 105 and requests each unit to process.

The data storage unit 103 is a shape storage unit 30.
1, viewpoint data storage unit 302, light source data storage unit 30
3. The calculation condition storage unit 309 is included. Shape memory unit 3
As shown in FIG. 2, in 01, shape data composed of coordinate data, which represents a shape element 401 of an object to be displayed by coordinate values in a three-dimensional space, parameters, and the like is stored.

The shape element 401 is, for example, a triangle or a sphere. In the case of a triangle, it is represented by coordinate data of three vertices, and in the case of a sphere, it is represented by data of center coordinates and radius.
As shown in FIG. 3, the parameters include surface data such as surface roughness and reflection coefficient related to the illumination effect of the shape element.

As shown in FIG. 4, the viewpoint data storage unit 302 stores the position of the viewpoint in the three-dimensional space, the direction of the line of sight,
Position data 501 representing the rotation inclination of a rectangular screen in the form of matrix data, view angle data 502 corresponding to a solid angle representing the field of view (for example, the view angle of a camera), and the size of a screen when an image is generated. Screen size 50
Data such as 3 is included.

In the light source data storage unit 303, the light source type 6
02, the light source position 603, the spread angle 604 of the light source in the case of a spot light source, the light source brightness 605, the brightness 606 of the ambient light of the light source, the direction of the light source, and the like. As the light source type 602, for example, a parallel light source assuming that the light source is at an infinite point, a point light source that emits light from one point in all directions,
A spot light source having a light emission direction and a spread with respect to a point light source can be considered. Also, the light source data for each light source is stored in a table 601 so that a plurality of light sources can be used at the same time.
Can be stored in the form of.

As shown in FIG. 6, the calculation condition storage unit 309 stores the calculation conditions necessary to calculate the illumination. That is, as shown in the figure, the light source type 701 and the position data 7 of the designated point of the display image that is the target of illumination calculation
02, a light source direction 703, a light source distance 704 indicating a distance to the light source, a light source brightness 705, a surface brightness 705 that specifies the brightness of the surface of a display object, and whether or not there is a user's instruction regarding these values is stored. A highlight designation flag 707 and an instruction condition flag 708 are included.

The detailed configuration of each unit will be described below along with the operation. First, the general operation will be described with reference to an example of the interactive screen displayed on the display device 104 shown in FIG. The light source in the figure is shown for the sake of explanation, and may not be displayed as an image. The user gives an instruction to the system by using the cursor 201, the menu 203, etc. displayed by the input device 105. Normally, the image generation unit 304 is instructed to first search each data in the shape storage unit 301, the viewpoint data storage unit 302, and the light source data storage unit 303 to generate a desired image. Image generator 30
Reference numeral 4 refers to each data to generate a two-dimensional image based on the three-dimensional shape data of the object to be displayed. The generated image is displayed on the display device 104 via the image display unit 305. The user inputs a change condition to the input control unit 308 via the input device 105 when the highlight position 202 where the brightness is desired to be the strongest and the brightness of the displayed image 204 of the object are desired to be changed. The user can give instructions and commands necessary for image generation using the cursor 201, menu 203, etc. displayed on the screen. An example of the menu is shown in FIG. For example, when the highlight position 202 of the image 204 of the displayed object is specified and the maximum brightness value is to be set at that position, the cursor 201 is moved to indicate that point, and then the highlight instruction on the menu is displayed. ON "
To The input control unit 308 stores the instructed condition in the calculation condition storage unit 309, and then requests the light source condition determination unit 307 to calculate the condition of the light source according to the changed condition. The light source condition determination unit 307 requests the shape selection / normal direction calculation unit 306 to obtain the shape of the object corresponding to the point indicated by the cursor 201 and the normal direction of the object surface at the position of the point. Then, based on the shape and the normal direction obtained by the shape selection / normal direction calculation unit 306, the calculation condition stored in the calculation condition storage unit 309, and the viewpoint data stored in the viewpoint data storage unit 302,
The conditions of the light source are determined by calculation according to the procedure described later. The light source data storage unit 3 indicates the changed conditions of the determined light source.
After storing the data in 03, the input control unit 308 again requests the image generation unit 304 to generate an image, and the image with the changed lighting effect is displayed on the display device 104. Similarly, the brightness (surface brightness) and color of the highlight position 202 and the brightness and color of the other surface of the object image 204 other than the highlight position can be designated by the menu 203. In this way, the user automatically indicates the light source position,
Since the light source data such as the direction and the brightness is calculated and the content of the light source data storage unit 302 is rewritten, the illumination effect desired by the user can be easily added to the image.

Here, the contents of the processing performed by each part of the central processing unit 101 will be described with reference to FIGS. 9 to 14. FIG. 9 shows a processing flow of the input control unit 308. The user uses the input device 105 to request various processes from the system. Here, the process of changing the illumination effect for the display image will be described. When there is an input, the input control unit 308 determines in step 801 whether or not it is the position input of the designated point by the cursor. If it is a position input, step 8
The calculation condition storage unit 309 stores the position data input in 07.
Position data 702. Next, in step 808, it is determined whether the designated point is accompanied by a highlight designation.
If it is a highlight instruction, the highlight designation flag 707 is turned on in step 809. If it is not a highlight instruction, the highlight designation flag is turned off in step 810. The menu 20 is used to judge whether it is a highlight instruction.
Judgment is made by inputting the command of 3.

If the input is not the position input in the determination of step 801, the process proceeds to step 802 and it is determined whether or not the input is the designation of the light source type. If yes, step 81.
Type of light source input in 1 (parallel light source, point light source, etc.)
Is stored in the light source type 701 of the calculation condition storage unit 309 and set. If it is not the designated input of the light source type, step 8
In 03, it is determined whether or not the input is the lightness designation of the designated point. In the affirmative, the lightness input in step 812 is set as the surface lightness 706 of the calculation condition storage unit 309.
If it is not the input for specifying the brightness, it is determined in step 804 whether or not the input is for specifying the brightness of the light source. If the input is to specify the brightness of the light source, the specified light source brightness is calculated in step 813 as the light source brightness 70 of the calculation condition storage unit 309.
Set to 5.

If it is determined in step 804 that the input does not specify the brightness of the light source, the flow advances to step 805 to determine whether the input is an input that specifies the distance from the designated point to the light source. If the distance is designated, the distance to the light source is set in the light source distance 704 of the calculation condition storage unit 309 in step 814. On the other hand, if the input is not to specify the light source distance, it is determined in step 806 whether or not the instruction is to set / cancel calculation conditions. If it is an instruction to set / cancel, in step 815, the flag of the instruction condition flag 708 is set (set) / unset (released). When the instruction condition flag 708 is set, the light source condition determining unit 307 uses the corresponding condition data when determining the condition of the light source.

In this way, when there is any input to the input control unit 308, in step 816, the light source condition determining unit 307 calculates the light source condition according to the instructed condition, and the light source data storage unit 307 calculates the light source condition. Instruct to change the data of 303. Based on this instruction, the light source condition determining unit 30
7 calculates new light source data according to the procedure of FIG. 10 and changes the data of the light source data storage unit 303. When this change is completed, the input control unit 308 requests the image generation unit 304 to generate a new image after the change in step 817.

Next, the processing operation of the light source condition determining unit 307 is shown in FIG. First, a method of calculating light source data in the light source condition determining unit 307 will be described with reference to FIG. The relationship between the brightness of the surface of the object, the viewpoint data, the light source data, and the surface reflection attribute of the object can be represented by the shading equation (Equation 1, Equation 2, Equation 3) shown in the following equation.

[0026]

[Equation 1]

[0027]

[Equation 2]

[0028]

[Equation 3]

In these equations, Ka, Kd, and Ks are the reflection coefficients of the surface, that is, the ambient light reflection coefficient, the diffuse reflection coefficient, and the specular reflection coefficient, respectively, which are constants determined by the surface attributes. n is the surface roughness coefficient, Isorg is the light source luminance, and Ia is the ambient light luminance. N is the normal vector of the pointing point, Is is the direction vector of the light source, V is the direction vector to the viewpoint, and d is the distance between the pointing surface and the light source. Cd0, Cd1 and Cd2 represent coefficients when the intensity of light from the light source is attenuated according to the distance. The value I obtained by Equation 1 is the surface brightness (color) of the object. Each vector is a unit vector. The brightness Ia of ambient light and the light attenuation coefficients Cd0, Cd1, and Cd2 are constants determined by the environment. The light source condition determining unit 307 includes the calculation condition storage unit 30.
The light source data such as the position and brightness of the light source is back-calculated using the above calculation formula so as to match the conditions designated by 9 and the contents of the shape storage unit 301 and the viewpoint data storage unit 302.

The process of the light source condition determining unit 307 is shown in FIG.
Follow along. In step 901, the calculation condition storage unit 3
The conditions necessary for calculation are read from 09. Step 902
Position data 70 to the shape selection / normal calculation unit 306.
The shape at the designated point position designated in 2 is selected, and a request is made to obtain the normal vector of the surface of the shape at the designated point. In response to this, the shape selection / normal vector calculation unit 30
6 executes shape selection and normal vector calculation according to the flowchart shown in FIG. Next, step 903.
Flag 707 as to whether or not the designated point is a highlight designation.
To judge. If it is a highlight instruction, step 90
4 otherwise, proceed to step 915.

In step 904, it is determined by referring to the light source type 701 whether the light source for the change instruction is a parallel light source or a point light source. If it is a parallel light source, the process proceeds to step 905, and if not, the process proceeds to step 908.

At step 905, it is judged whether or not the lightness of the designated point is designated by referring to the designated condition flag 708 corresponding to the surface lightness 706. If the brightness is set, the process proceeds to step 906, and if not set, the process proceeds to step 907.

In step 906, the designated point is set as the highlight position, the light source is a parallel light source, and the surface brightness at the highlight position becomes the value of the specified surface brightness 706.
Calculate the direction and brightness of the light source. For highlighting, the vector Is representing the direction of the light source may be obtained so that the vector H and the vector N of the equation 1 are the same. This condition is satisfied by the following equation (4). In the equation, each vector is a unit vector.

[0034]

[Equation 4]

Next, in order to obtain the brightness of the designated point, Equation 1
Substituting the value of the specified surface brightness 706 into I of, the luminance Isorg of the light source corresponding to this is obtained. Since the light source is a parallel light source, there is no attenuation due to distance, and Cd1 and Cd2
Is 0 in each case. In step 926, the direction and brightness of the light source thus obtained are set in the corresponding area of the light source data storage unit 303.

When the process proceeds to step 907, the lightness is not specified, and therefore the light source direction I is determined by the above-described procedure.
Only s is obtained, and the obtained direction of the light source is set in the corresponding area of the light source data storage unit 303 in step 926.

When the process proceeds to step 908, similarly to step 905, it is determined whether the brightness of the designated point is designated. If it is specified, the process proceeds to step 909, and if not specified, the process proceeds to step 914. Step 90
At 9, it is determined whether or not the brightness of the light source is designated.
This determination is made by the instruction condition flag 708 corresponding to the light source luminance 705 of the calculation condition storage unit 309. If the light source brightness is specified, step 910 is executed, and if not specified, step 911 is executed.

In step 910, the light source is a point light source, the brightness of the value specified in the light source brightness 705 is used to highlight the designated point, and the brightness of the designated point is designated as the surface brightness 70.
The direction of the light source and the distance from the designated point to the light source are obtained using the above calculation formula so that the value becomes 6. in this case,
Since the light source is a point light source, the attenuation coefficients Cd0, Cd1, C
Consider d2.

In step 911, it is determined whether or not the distance from the designated point to the light source is designated. This determination is performed by referring to the instruction condition flag 708 corresponding to the light source distance 704 of the calculation condition storage unit 309. If the distance to the light source is specified, step 912 is executed, and if not specified, step 13 is executed.

In step 912, the light source is a point light source, the distance from the designated point to the light source is the value set in the light source distance 704 of the calculation condition storage unit 309, the designated point is highlighted, and the lightness is designated as the surface lightness 706. The direction and brightness of the light source are calculated by using the above equation so that the values become different. In step 926, the obtained light source data is set in the light source data storage unit 303 as described above.

Step 913 is executed when a plurality of highlight positions are set on the object surface. Therefore, after the indicating conditions for a plurality of indicating points are input and aligned, the mathematical equation 1 is applied to each indicating point to establish a simultaneous equation and perform the calculation. Since the brightness at each highlight position is specified in the calculation, the position of the light source, that is, the direction and distance, and the brightness of the light source are determined so as to satisfy them. Step 91
In 4, the brightness of the highlight position is not specified, so
A simultaneous equation is set up so as to satisfy the highlight position, and the direction and distance of the light source are obtained so as to satisfy the specified conditions for a plurality of designated points.

In step 915, similarly to step 904, it is determined by referring to the light source type 701 whether the light source for the change instruction is a parallel light source or a point light source. If it is a parallel light source, the process proceeds to step 916, and if not, the process proceeds to step 919. In step 916, similarly to step 905, it is determined whether or not the lightness of the designated point is designated by referring to the designated condition flag 708 corresponding to the surface lightness 706. If the brightness is set, the process proceeds to step 917, and if not set, the process proceeds to step 918.

In step 917, the light source is a parallel light source,
The light source luminance is calculated so that the surface brightness of the designated point becomes the specified surface brightness 706. In step 918, an error is displayed because calculation cannot be performed due to insufficient calculation conditions.

In step 919, as in step 905, it is determined whether or not the brightness of the designated point is designated as the surface brightness 7.
The determination is made by referring to the instruction condition flag 708 corresponding to 06. If the brightness is set, the process proceeds to step 920, and if not set, the process proceeds to step 925.

In step 920, similarly to step 909, it is determined whether or not the brightness of the light source is designated.
This determination is made by the instruction condition flag 708 corresponding to the light source luminance 705 of the calculation condition storage unit 309. If the light source brightness is specified, step 921 is executed, and if not specified, step 922 is executed.

In step 921, the distance to the light source is calculated so that the light source is a point light source, the light source brightness is the value of the light source brightness 705, and the brightness of the designated point is the value of the surface brightness 706.
In step 922, similarly to step 911, it is determined whether or not the distance to the light source is designated by referring to the corresponding instruction condition flag 708. If it is designated, step 923 is designated, and if it is not designated. Is step 92
Execute 4 respectively.

In step 923, the light source is a point light source, the distance to the light source is the distance specified by the light source distance 704, and the brightness of the pointing point is the specified surface brightness 706 based on the above equation. The distance to the light source. In step 924, the illumination by a plurality of point light sources is considered and a plurality of point instructions are given to obtain the positions and brightness of those light sources. In step 925, an error is displayed because calculation cannot be performed due to insufficient calculation conditions.

In step 926, the light source condition obtained by the above calculation is set in the light source data storage unit 303.

Next, the processing of the shape selection / normal calculation unit 306 will be described with reference to FIG. This process is called and executed by the light source condition determining unit 307, the shape of the object corresponding to the designated point is selected from the shape storage unit 301, the normal vector at the designated point of the shape is obtained, and the light source condition determining unit 30 is obtained.
It is supposed to return to 7. That is, step 110
In step 3, one piece of shape data at the position corresponding to the designated point is read from the shape storage unit 302. In step 1104, the read shape is converted into a viewpoint coordinate system based on viewpoint data. As a result, it is determined in step 1105 whether or not the shape is drawn at the designated point on the screen. If it is drawn, the process proceeds to step 1106. If not, the process proceeds to step 1108. In step 1106, the normal vector of the surface of the shape corresponding to the designated point is calculated, and the calculation result is returned to the light source condition determining unit 307 in step 1107.
In step 1108, it is determined whether or not there is a shape to be drawn in the shape storage unit 301, and if it exists, the processing returns to step 1103 and is repeated. If it does not exist, it returns to the light source condition determining unit 307 that the shape could not be selected in step 1109.

The processing of the image generator 304 will be described with reference to FIG. First, in step 1201, shape data is read from the shape storage unit 301, viewpoint data is read from the viewpoint data storage unit 302, and light source data is read from the light source data storage unit 303. Next, in step 1202,
The color calculation of the points on each screen is executed using the shading equation of Equation 1 for all the shape elements. The result is transferred to the image display unit 305 in step 1203.

In the image display unit 305, as shown in FIG. 14, the point data of each screen transferred in step 1301 is fetched, and in step 1302 the display device 1 is fetched.
Write the color to the corresponding screen point 04. In this way, the user directly specifies the position on the image and specifies the lighting effect at that position, and the conditions such as the position, direction, and brightness of the light source that realize the lighting effect are automatically calculated. Since the lighting effect of the display image is changed based on the result, a desired image can be easily obtained.

[0052]

As described above, according to the present invention,
In computer graphics, when setting the lighting effect of the display image, the desired lighting effect can be achieved by directly designating the desired highlight position and brightness without designating the position of the light source in the coordinates of the three-dimensional space. Obtainable.

[Brief description of drawings]

FIG. 1 is an overall system configuration diagram of an embodiment of the present invention.

FIG. 2 is a diagram showing an example of data contents of a shape storage unit.

FIG. 3 is a diagram showing an example of surface data of a shape of a shape storage unit.

FIG. 4 is a diagram showing an example of data contents of a viewpoint data storage unit.

FIG. 5 is a diagram showing an example of data contents of a light source data storage unit.

FIG. 6 is a diagram showing an example of data contents of a calculation condition storage unit.

FIG. 7 is a diagram showing an example of a display screen according to an embodiment of the present invention.

FIG. 8 is a diagram showing an example of a menu.

FIG. 9 is a flowchart showing a processing procedure of an input control unit.

FIG. 10 is a flowchart showing a processing procedure of a light source condition determining unit.

FIG. 11 is a diagram illustrating a calculation based on a shading equation.

FIG. 12 is a flowchart showing a processing procedure of a shape selection / normal calculation unit.

FIG. 13 is a flowchart illustrating a processing procedure of an image generation unit.

FIG. 14 is a flowchart illustrating a processing procedure of an image display unit.

[Explanation of symbols]

 101 central processing unit 103 data storage device 104 display device 105 input device 301 shape storage unit 302 viewpoint data storage unit 303 light source data storage unit 304 image generation unit 305 image display unit 306 shape selection / normal calculation unit 307 light source condition determination unit 308 Input control unit 309 Calculation condition storage unit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshifumi Fukuda 7-1, 1-1 Omika-cho, Hitachi-shi, Ibaraki Hitachi Ltd. Hitachi Research Laboratory

Claims (5)

[Claims] 1. Shape data representing a shape of an object to be displayed, viewpoint data for setting a viewpoint condition of a display image such as a viewing position and direction of the object, and an illumination effect on the display image of the object. Storage means for storing light source data for setting conditions of a given light source; and image generation means for generating a display image of the object based on the shape data, viewpoint data and light source data stored in the storage means. A computer graphics system comprising a display unit for displaying the display image generated by the image generating unit, and an input unit for inputting a lighting request command for directly setting a lighting effect on the surface of the object of the display image. And a light source condition determination for rewriting the corresponding light source data of the storage unit by obtaining the condition of the light source satisfying the illumination request command input from the input means. A computer graphics system characterized by having a fixing means. 2. The computer graphics system according to claim 1, wherein the object has a three-dimensional shape, and the image generation means converts the three-dimensional shape into a two-dimensional image to generate the two-dimensional image. 3. The illumination request command according to claim 1, further comprising a command for designating an arbitrary point for setting a high surface brightness of the object of the display image, and the light source condition determination when the command is input. A computer graphics system, wherein the means adjusts the position of the light source. 4. The illumination request command according to claim 1, further comprising a command for designating the value of the surface brightness, wherein the light source condition determining means adjusts the brightness of the light source when the command is input. Computer graphics system characterized by. 5. The illumination request command according to claim 1, further comprising a command for designating a value of the surface luminance, and when the command is input, the light source condition determining means causes the distance between the light source and the object. A computer graphics system characterized by adjusting.