JP2728312B2 - Computer graphic system and object display attribute setting method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to a computer graphic system for performing graphic processing and image processing, and in particular, when displaying an object on a screen, a material such as a metal or a plastic. The present invention relates to a method for setting an object display attribute suitable for easily designating an object.

[Related Art] When displaying a three-dimensional object using a three-dimensional computer graphic system or the like, the display is performed so that the user can know what the material of the object to be displayed is, for example, whether the object is metal or plastic. There is a need to. Conventionally, when the material texture is specified by the operator, see page 390 of "Basic Procedures and Practices of Practical Computer Graphics" published by Nikkan Kogyo Shimbun, translated by David F. Rogers, Electronics Division of Seiko Electronic Industry Co., Ltd. As described, the intrinsic color of the object and the reflected light component are specified without distinction. When specifying the color of an object with the ambient light component, the diffuse reflection light component, and the specular reflection light component,
Red (R), green (G), blue (B) or hue (H), lightness (L), and saturation (S) are designated. This is the same in the prior art described in JP-A-64-6998, in which the ambient light component is designated by a combination of R, G, and B, and the diffuse reflected light component is designated by a combination of R, G, and B. , The specular reflected light component is also R,
It is specified by the combination of G and B.

[Problems to be Solved by the Invention] The above-described prior art includes an ambient light component, a diffuse reflected light component,
Since the specular reflected light component is specified by combining R, G, B (or H, L, S, etc.), the number of parameters to be used is as many as 9, so that the material appearance of the object can be displayed accurately. It is possible. However, on the other hand, it is difficult to appropriately set the value of each parameter, and there is a problem that an accurate material appearance cannot be displayed unless a skilled expert is used.

In recent years, the demand of general users for CAD systems for designing designs and generating images for presentation of designed products has been increasing. However, conventional systems require skill in specifying the texture of an object, so to spread computer graphic systems in general,
This needs to be resolved.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a computer graphic system and an object display attribute setting method for easily specifying a material appearance of an object.

[Means for Solving the Problems] The object of the present invention is to display the material texture of an object illuminated by a light source on a screen, as ambient light components, diffuse reflection light components, and specular reflection light components as reflection attributes of the object surface. In a computer graphic system for designating a color tone, a designating means is provided as a user interface for interpolating the specular reflected light component between an object specific color and a light source color, and an interpolation command of the specular reflected light component is taken in from the designating means. Is achieved.

[Action]

Skill is required to make the specular reflected light the target specular reflected light by specifying each color component of RGB. However, in the present invention, the provision of the above-mentioned designation means makes it easy to perform interpolation adjustment to obtain the target specular reflection light by this designation means. The texture can be easily adjusted whether the reflected light is closer to the intrinsic color of the object or non-metallic (specular reflected light is closer to the light source color).

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

In the real world, the characteristics of light reflected from the surface of an object depend not only on the properties of the light source but also on the properties of the object surface. When expressing the texture of an object with a computer graphic system, a desired result is intended to be obtained by expressing the properties of the surface of the object. by the way,
Light reflected on the object surface is classified into diffuse reflected light and specular reflected light. Diffusely reflected light indicates a component in which light once enters an object and is re-emitted from its surface in all directions. Specularly reflected light reflects light off the surface of the object like a mirror.

In a computer graphic system, when determining the brightness or luminance of the surface of an object, the following equation is generally used.

I = Ia * Ka + Id * Kd * cos (A) + Is * Ks * W (B)
(1) I; determined brightness of object surface Ia, Ib, Is; parameters indicating characteristics of light source Ka; ambient light intensity Kd; diffuse reflected light intensity Ks; specular reflected light intensity Component) indicates a component illuminated from the surroundings other than the light source, and is a term for preventing a portion of the object not directly illuminated by the light source from being darkened.

The second term of the first equation (diffuse reflected light component) is expressed by Lambert (La
mbert) is a term indicating the cosine law, and is applied when light from a light source is reflected by perfect diffusion. cos
“A” in (A) is the angle between the normal to the object surface and the light source direction as viewed from the object surface. This term is a component indicating a color unique to the object such as plastic or gypsum.

The third term of the first equation is a term indicating a specular reflected light component, and W
“B” in (B) is the angle between the line of sight and the specular reflection direction on the mirror surface, and W (B) is a function indicating the attenuation rate when the line of sight deviates from the specular reflection direction. The specular reflected light component plays a large role in expressing the texture of the object. For example, for an object such as plastic, the specular reflected light component has the same color as the light source. That is, if the light source is white light, the specular reflection light of the plastic becomes white, and if the light source is red light, it becomes red. On the other hand, in the case of a metal, a solid dye, or the like, the specular reflected light has a color different from the color of the light source. For example, when copper is illuminated with white light, the specularly reflected light becomes the intrinsic color of copper, that is, red.

Ka, Kd, and Ks are vector information indicating color information, and each is represented by a combination of R, G, and B. By combining such Ka, Kd, and ks, various textures can be expressed. However, if Ka, Kd, and ks are designated by a combination of R, G, and B, respectively, as in the prior art, this designation requires considerable skill. Therefore, in the present embodiment, instead of specifying this Ka by the combination of R, G, and B, when the object color is represented by the (H, L, S) color system, Ka is represented by (H, α _a L , S) as 0 ≦ α _a ≦ 1. Similarly, specifying a _{Kd (H, α d, S} ) as 0 ≦ α _d ≦ 1 in. And Ks is 0 ≦ α of (H, α _s L, β _s S)
Specify as _s ≦ 1,0 ≦ β _s ≦ 1. Here, “no luster” is expressed as α _s = 0. Further, plastic is represented by β _s = 0, and metal is represented by β _s = 1. Then, the designated Ka, Kd, and Ks are each converted into a combination of R, G, and B by a computer. Where K
a and Kd are set to colors based on the intrinsic color of the object, and the reflection intensity can be set independently for each parameter. Further Ks
Is set to the intrinsic color of the object, white, or an intermediate color, and the reflection intensity can be set.

FIG. 1 is a configuration diagram of a main part of a computer graphic system according to an embodiment of the present invention. The object-specific color determination device 1 determines a unique color of an object. For example, when expressing the material feeling of red plastic or copper, “red” is set as the object-specific color. The object-specific color determination device uses the three primary colors of R, G, and B to determine a hue expressed by a “color” designated by an operator and its “intensity”. In this specification, in the present embodiment, as shown in FIG. 5, which will be described later, continuous specification can be performed in a sliding manner. May be used as the object-specific color.

FIG. 2 shows details of the surface reflection attribute device 2 shown in FIG.
The surface reflection attribute specifying device 2 includes an ambient light intensity determining device 3
Diffused light intensity determining device 4 and metallic texture adjusting device 5
And a specular reflected light intensity determination device 6.

The ambient light intensity (Ka) determination device 3 receives the RGB data indicating the object-specific color from the object-specific color determination device 1 and
Converts data to HLS color system data. Then, as described above, using α _a specified by the operator, (H, α _a L,
S) is obtained, and this is converted into data of the RGB color system, and Ka is calculated.

The diffuse reflection light intensity (Kd) determination device 4 also converts RGB data into HLS data, obtains (H, α _d L, S) from α _d specified by the operator, and converts this into RGB color system data. Convert and calculate Kd.

The metal texture adjusting device 5 also receives the RGB data, converts it into HLS data, and outputs the β data designated by the operator.
(H, L, β _s S) is obtained using _s . The next specular reflection light intensity (Kd) determination device 6 obtains (H, α _s L, β _s S) using α _s specified by the operator, converts this into RGB color system data, and calculates Ks. calculate.

FIG. 3 shows a state in which a sphere is illuminated by one light source. The above-mentioned Ka, Kd, and Ks determine the spread and brightness of each part of the sphere. In FIG. 3, the ambient light component is determined by the parameter Ka and represents the part not directly illuminated by the light source. The diffuse reflected light component is determined by the parameter Kd, and represents the part directly illuminated by the light source. The specular reflected light component is determined by Ks, and represents a portion where light from the light source is specularly reflected by the object surface and enters the viewpoint.

Next, a case where the unique color of the object is determined will be described. In general, when determining a color, a hue is represented by its intensity using three primary colors of RGB. However, in this embodiment, the intrinsic color of the color is determined using the HLS color system. FIG. 4 is an explanatory diagram of the HLS color system. H (hue), L (lightness), S (saturation)
When the three parameters are input, one color is determined. Here, the hue H takes a value of 0 to 360 degrees, where 0 degree is “red”, 60 degrees is “yellow”, 120 degrees is “green”, 180 degrees is “cyan”, and 240 degrees is “blue”. , 300 degrees is "magenta". Lightness L takes a value from 0.0 to 1.0, where 0.0 is "black" and 1.0 is "white"
In other cases, a color corresponding to the hue and saturation S is shown. Saturation S takes a value from 0.0 to 1.0, where 0.0 is "achromatic"
That is, “gray” is indicated, and 1.0 indicates “pure color”. Saturation S
Can be changed continuously to “gray” or “pure color” while maintaining “brightness” and “color”. With an appropriate combination of HLS, the operator can specify his intended color.

FIG. 5 is a configuration diagram of a user feeler face for material appearance setting. Each knob shown in FIG. 5 may use an actual slide volume or may simulately display it on a computer screen. The hue knob, the brightness knob, and the saturation knob are a set of three, and designate a unique color of the object. Red knob, green knob, blue knob,
In the same manner, the intrinsic color of the object is designated as a set of three. The set of the hue knob, the lightness knob, and the saturation knob and the set of the red, green, and blue knobs are related to each other, so that when one of the knobs is changed, the other knob is changed. Also change so as to be consistent. The operator specifies the unique color of the object by using the set of knobs that are easy to use.

Knobs for specifying the reflection attribute include an ambient light knob, a diffuse reflection light knob, a specular reflection light knob, and a metal texture knob.
In this embodiment, a surface roughness knob is provided. FIG.
FIG. 5 is a sectional view of the color solid shown in FIG. 4. The colors on this cross section all have the same saturation and include the intrinsic color of the object. When the brightness component of the object-specific color is changed by changing the ambient light knob, the value of Ka continuously changes from the object's own color to the black point as shown by the thick line. Diffuse light knob
Again, Kd is determined by changing the lightness component of the object-specific color.
The surface roughness knob is a knob that determines the spread of the specular reflection component (see FIG. 3). As shown in FIG. 7, the metal texture knob is a knob for changing the saturation component of the intrinsic color of the object, and the result continuously changes from the intrinsic color to the achromatic color (gray). When the metal texture knob is moved to the metal side, it approaches the object-specific color side, and when it is moved to the plastic side, it approaches the achromatic color side. As shown in FIG. 7, the specular reflection light knob changes the lightness component of the color determined by the metal texture knob and determines Ks.

FIG. 8 is a block diagram of a user interface different from that of FIG. In this embodiment, the operator specifies the object-specific color and the reflection attribute from the menu displayed on the screen. In the embodiment of FIG. 5, each parameter can be specified continuously, but in this embodiment, the value of each parameter is specified as a discrete value. When an operator is designated, object-specific colors and reflection attribute data corresponding to the designated menu are read out from the storage device, and Ka, Kd, and Ks are determined by the devices shown in FIG.

Note that the user interface shown in FIG. 5 and the user interface shown in FIG. 8 can be combined. For example, the operator selects an object-specific color using the user interface shown in FIG. 5, and uses the user interface shown in FIG. 8 or the reverse as the reflection attribute.
Further, it is also possible to adopt a configuration in which a rough selection of the object-specific color and the reflection attribute is selected by the operator in a menu format, and detailed settings are selected by the user interface shown in FIG.

Next, using the user interface shown in FIG. 5,
A method of obtaining a material appearance of a typical object will be described.

When expressing an object that emits light by itself, first, a set of a hue knob, a brightness knob, and a saturation knob, or a red knob,
The emission color of the object is designated using a pair of a green knob and a blue knob. Next, the ambient light knob is set to a sufficiently large value. The sufficiently large ambient light component expresses the material feeling of the light emitting object. The knobs for specifying the reflection attribute (the knobs for diffuse reflection, specular reflection, surface roughness, and metallic texture)
Set appropriately according to your preference.

Even when expressing a matte object such as gypsum, first, the intrinsic color of the object is determined. The specular reflection knob is set to the lowest value to suppress the gloss display. The diffuse reflection light knob is set appropriately to adjust the brightness of the illuminated part. Then, the brightness of the non-illuminated portion is adjusted using the ambient light knob.

When expressing a glossy plastic object, first specify the unique color of the object. Adjust the Ambient Light Knob and Diffuse Reflection Light Knob in the same way as for gypsum, set the metal material knob to the plastic side, set the color of the specular reflected light component to achromatic, and set the specular reflected light knob appropriately. Adjust the brightness of the glossy part. Further, the spread of the glossy portion is adjusted using the surface roughness knob. In this case, since Ks is set to an achromatic color, the specular reflection component becomes the same color as that of the light source, regardless of the specific color of the object.

When expressing a glossy metal object, first, the intrinsic color of the object is determined. The diffuse reflection light knob is normally set to the lowest value to suppress the diffuse reflection light. The ambient light knob is appropriately set in consideration of the image effect. The metal texture knob is set to the metal side to make the specular reflected light component an object-specific color, and the specular reflected light knob is appropriately set to adjust the brightness of the glossy portion.
Further, the spread of the glossy portion is adjusted using the surface roughness knob. In this case, since Ks is set to the object-specific color, for example, when illuminated with white light, the specular reflected light component becomes the object-specific color.

In the embodiment described above, in order to adjust the ambient light component intensity, the diffuse reflected light component intensity, and the specular reflected light component intensity, the HLS
Although the lightness L component of the color system was changed, the present invention is not limited to this embodiment, and any method of changing any component of any color system may be used as long as the method changes the light intensity. Good. For example, in FIG. 6, the same effect can be obtained by changing the straight line connecting the object-specific color and the black point. Further, although the embodiment in which the saturation component of the HLS color system is changed to adjust the color of specular reflection by the metal texture knob has been described, the present invention is not limited to the embodiment, and the achromatic color Any method may be used as long as the method interpolates between the object and the object-specific color. For example, in FIG. 7, the same effect can be obtained by changing the straight line connecting the object-specific color and the white point.

[Effects of the Invention] According to the present invention, if the intrinsic color of an object and the light source color are determined, it is metallic (specularly reflected light is closer to the intrinsic color of the object) or non-metallic (specularly reflected non is closer to the non-source color). The texture can be easily adjusted.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a main part of a computer graphic system according to an embodiment of the present invention, FIG. 2 is a detailed configuration diagram of a surface reflection attribute designation device shown in FIG. 1, and FIG. 3 is illuminated by a light source. FIG. 4 is a diagram showing the state of a sphere, FIG. 4 is an explanatory diagram of an HLS color system, FIG. 5 is an explanatory diagram of a user interface, FIG. 6 is an explanatory diagram of effects of an ambient light knob and a diffuse reflection light knob, and FIG. FIG. 8 is an explanatory view of the effect of the metal texture knob and the specular reflection knob, and FIG. 8 is an explanatory view of a user interface according to another embodiment. DESCRIPTION OF SYMBOLS 1 ... Object specific color determination device, 2 ... Surface reflection attribute designation device, 3 ... Ambient light intensity determination device, 4 ... Diffuse reflection light intensity determination device, 5 ... Metal texture adjustment device, 6 ... Specular reflection Light intensity determination device.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Toshio Sakai 4026 Kuji-cho, Hitachi City, Ibaraki Prefecture Inside Hitachi, Ltd.Hitachi Research Laboratory (72) Inventor Akihiro Sakamoto 4026 Kuji-cho, Hitachi City, Ibaraki Prefecture Hitachi Research, Ltd. Office (72) Inventor Kenjiro Sato 4026 Kuji-cho, Hitachi City, Ibaraki Prefecture Inside Hitachi Research Laboratory, Hitachi, Ltd. (72) Inventor Tsugio Tomita 4026 Kuji-cho, Hitachi City, Ibaraki Prefecture, Hitachi Research Laboratory, Hitachi, Ltd. (56) References JP-A-1-263886 (JP, A) JP-A-62-14270 (JP, A) Full-color 3D graphics StrataVision3D made by Macintosh, monthly ASCII May 1990, P.A. 321-328 Shibamoto, Yasuda 'Development of high quality CG software TRIMAGEINE running on a personal computer', PIXEL (No. 84), September 1989, p. 103-109

Claims (2)

(57) [Claims] When a material appearance of an object illuminated by a light source is displayed on a screen, an ambient light component,
A computer graphic system for designating a color tone of a diffuse reflection light component and a specular reflection light component, comprising a designation means for interpolating the specular reflection light component between an object-specific color and a light source color. 2. The method according to claim 1, further comprising the steps of: displaying a material texture of the object illuminated by the light source on a screen;
In the object display attribute setting method for designating the color tone of the diffuse reflected light component and the specular reflected light component, the method comprises the steps of: interpolating the specular reflected light component between an object-specific color and a light source color based on an interpolation command input from a user interface. An object display attribute setting method, comprising: setting a specular reflected light component.