JP2007052758A - Ambient light mapping circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To determine reflection luminance distribution, with consideration given to a light-shielding object against ambient light and the distance between a mapping point and a light source, and to determine a diffuse reflection component from the entire rendering space in real time. <P>SOLUTION: A light source distributed in a global space is projected onto six faces of an ambient cube to store the distribution luminance, and a visual line reflection vector is calculated from interpolation of a polygon to determine a point intersecting the cube faces. Then, the luminance is read from the cube memory and an object in a space in the cube is projected onto each of the six faces of the cube. There is provided a cube shadow polygon buffer for storing the distance of the object from the cube faces by using a hidden surface removal method. Presence of a light-shielding object between the interpolation point and the cube faces is determined, luminance from the cube faces is masked, cube face luminance is scaled by using the distance from the cube faces and the light-shielding object to the interpolation point, a plurality of reference points are defined on the cube faces, and a diffused light component is determined by totalizing the luminance from the reference points at the interpolation point. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to computer graphics video technology, and belongs to the field of an algorithm for rendering the reflected luminance of an object surface by irradiation of ambient light, and a circuit technology and apparatus for implementing the algorithm.

  In computer graphics, the implementation of a global lighting model that takes into account the reflection characteristics unique to an object is an important issue in expressing highly realistic images. The big factor that often impairs the reality of computer graphics images compared to live-action images today is the principle of global interpolation (reflection by ambient light), which is the mainstream of real-time rendering. Because it is not suitable. The only process for obtaining the global lighting effect in the polygon rendering method is the environment mapping method, which sets an environment cube (hexahedron) surrounding the object for an object having specular reflection characteristics. With the center as the projection center, peripheral images outside the cube are projected onto each of the six surfaces, the projection view is converted into a texture pattern, and then this pattern is mapped to an object. In the real world, there are, for example, ceiling fluorescent lamps, wall windows, and walls with indirect reflected light, and these direct or indirect lights affect the luminance of all object surfaces in the room. As a means for expressing this, there is a method in which the conventional environment cube mapping method is applied, a light source (luminance) distribution pattern is drawn on the environment cube instead of a peripheral object image, and this is mapped to a drawing object. However, this method has two fatal problems. One is a part of the light reflected by the object in which the reflection position moves with the viewpoint direction. In the conventional environment mapping algorithm, since the projection centers are all the cube centers and the position of the line-of-sight reflection point is not considered, it is impossible to maintain the geometric accuracy with respect to the mapping position. The second problem is that the influence of global lighting is not on specific objects but on all objects, and the conventional method of defining an environmental cube for each object has a small memory capacity for storing cube patterns. Realistic size. As a means to deal with the latter problem, it is conceivable to define one environment cube in the entire space and apply it to all objects. The problem in this case is that the light shielding relationship between objects cannot be determined from only one environmental cube. From this background, to date, environmental light is considered as well, and all objects have reflection characteristics with respect to some ambient light. Can't see.

  The present invention defines a global environmental light cube having a luminance distribution as an environmental cube pattern, and uses the means for mapping the cube to an object in the space in the cube.

In order to solve each of the problems described above, the light-shielding object determination means for the interpolation point (also referred to as a drawing point or a rendering point) and the illumination luminance from the cube plane taking into account the position of the interpolation point are determined. It is an object of the present invention to realize the means.

  In the present invention, the brightness in the global space is projected onto the six surfaces of the ambient light cube, and the pattern is stored in a memory (hereinafter referred to as cube memory). The difference in the expression between the ambient light mapping or ambient light cube in the present invention and the conventional environment mapping or environment cube is that the information stored in the environment cube is not the object shape but the luminance distribution. . The distribution pattern of light sources in the global space is mainly targeted for indoor fluorescent lamps and lighting from windows, and the luminance distribution illuminated by these is stored in cube memory. Outside the room, the brightness is due to the sky or streetlight. In the present invention using the polygon rendering method, an object is drawn as a set of a large number of polygonal surfaces, and vertex coordinates, texture coordinate values, light source incident vectors, surface normals, and line-of-sight vectors (viewpoints and multipoints) are assigned to each polygon vertex. Define the direction that connects the corner vertices). By interpolating these vertex definition variables, each of the vertex definition variables is obtained at each point inside the polygon, and the reflection vector of the line of sight is obtained from the surface normal and the line-of-sight vector, and the reflection point (interpolation) The point where the reflection vector intersects the cube surface is obtained from the coordinate value of the point) and the size of the side of the cube (or indoor space in the case of indoors), and the luminance is read from the cube memory, and this luminance is used as the interpolation point. Ambient light can be obtained by mapping. When mapping, it is possible to adjust the degree of illumination by ambient light on the object surface by linearly synthesizing the brightness of the pattern and the object brightness using the surface attribute of the object, or by scaling the brightness of the cube memory it can.

  On the other hand, with the above method alone,

It does not solve the problem caused by the light shielding object described in. When the light-shielding object exists between the interpolation point and the cube plane intersection of the viewpoint reflection vector, the illumination from the cube surface to the interpolation point should be attenuated as the distance decreases. In the present invention, in order to make it possible to determine the presence or absence of a light-shielding object, each cube plane is projected on the projection plane (the viewpoint is on an axis outside the cube space perpendicular to the cube plane in the first pass, as in the case of generating a two-pass shadow. ), The object in the cube space is drawn using the hidden surface elimination method, and the distance (hereinafter referred to as the depth value) to the cube surface of the object closest to the cube surface is stored in the shadow polygon buffer. As a result, six sets of shadow polygon buffers are required for six cube surfaces. In the present invention, this shadow polygon buffer is called a cube shadow polygon buffer (hereinafter referred to as CSPB). In the actual implementation, the relationship between the global light source and the object is usually considered that the majority of the object has little geometrical movement in its position and shape. Even if it is known, it does not have a big influence on drawing performance practically. The same applies to the cube memory. If the object moves dynamically, it is necessary to refresh the CSPB for each movement in order to accurately determine the light-shielding relationship. Since the shadow generation by is processed in parallel, there is also a method in which the update of the global illumination is pending during that period and is resumed after being stationary. Such a response is sufficient for many applications.

When drawing on the CSPB is completed, an object in the environment cube space is drawn in the viewpoint coordinate system in the second pass. At this time, the reflection vector R is obtained by the equation (1) from the surface normal N of the polygon vertex, the viewpoint vector V, and the coordinate value P ₀ of the line-of-sight reflection point, and the intersection Pcross with the cube is obtained by the equation (2). . These equations can be implemented with four arithmetic units. The linear parameter t in equation (2) is determined from the intersection plane, the reflection point coordinate value, and the size of the cube. The intersection calculation between the cube surface and the reflection vector is a general intersection calculation between a plane and a straight line, and various high-speed algorithms can be considered, but the intersection calculation algorithm itself is not within the scope of the present invention.
R = 2N (N · V) −V (1)
Pcross = P ₀ + Rt (2)

  Rendering the object in the viewpoint coordinate system in the second pass, and using the interpolated interpolation value, the cube surface where the line-of-sight reflection vector intersects by the equations (1) and (2), and the intersection coordinate value in the surface are obtained. When the intersecting cube plane is determined, the interpolation point (X, Y, Z) coordinates are converted into the coordinate system (Xl, Yl, Zl) of the plane. Next, the distance Zd is read from the coordinate (Xl, Yl) and the CSPB of the corresponding surface, and this is compared with Zl. If Zl is closer to the surface than Zd (and Zd = Zl), then from the cube memory When the luminance is read out and mapped to the interpolation point, and Zl is located far away, the interpolation point is masked (not mapped) as being located behind the light-shielding object. Note that the conversion of the interpolation points into cube plane coordinate values (Xl, Yl, Zl) can be omitted by defining six cube plane coordinate values together with the viewpoint coordinate values at the vertices in the second pass. It is.

When mapping the luminance of the intersection to the interpolation point, the present invention combines the luminance of the intersection with the luminance of the object to be mapped. The brightness of the object is the brightness of the object surface obtained by an illumination model (for example, BRDF model) based on a process different from environment mapping. If this is I _b, and the brightness read from the cube memory is I _c , The luminance I _{p according} to the equation (3) is determined using the uniquely defined synthesis coefficient α.

  In the present invention, since the distance (Zl−Zd) between the interpolation point and the light shielding object can be calculated for each interpolation interpolation of the polygon, when this distance exceeds a predetermined value,

A distance scale function (for example, a function that approaches 0 when the distance approaches zero and moves toward 1 when the distance approaches zero, but is regarded as the same object when Zl = Zd, and is set to 1). And the cube memory brightness is multiplied by this function value. Means for making this multiplication value the luminance from the cube plane of the interpolation point is also provided. This distance scale function expresses a wraparound characteristic of ambient light that is assumed to be a shadow if the interpolation point is located immediately after the light-shielding object and is not affected by the light-shielding object if it is far away.

（４）式のｋは係数である。この結果、本発明ではキューブ面からの距離が遠い視線反射点では、近い点に比較し輝度分布がボケて広がる表現が可能となる。（４）式のβは１例を示したものであるが、１／（１＋ｋ_０ｘＤ＋ｋ_１ｘＤ^２）など現実の環境光の影響に類似した関数（ｋ_０，_１はそれぞれ係数）を設定することもできる。On the other hand, as the distance between the interpolation point and the cube luminance surface becomes larger, there is usually a phenomenon in the real world where the luminance pattern distribution at the interpolation point is thinly diffused depending on the area and shape of the light source. As a means for expressing this, one creates a relatively clear representation of the light source shape of the ceiling or wall, and the other creates two blurred patterns by filtering this and stores them in the cube memory. . That is, in the present invention, two light distribution patterns I _c0, one that clearly expresses the presence or shape (locality) of the light source (one that is close to the surface) and one that is blurred (one that is away from the surface). And I _c1 as cube plane patterns, respectively, and when drawing an object, these two patterns are read simultaneously, and the weight D between the two patterns is calculated using the distance D between the interpolation point and the cube plane intersection (4 ) And the luminance I _c is set as cube luminance.

In equation (4), k is a coefficient. As a result, in the present invention, it is possible to express that the luminance distribution is blurred and widened at the line-of-sight reflection point that is far from the cube surface as compared to the near point. Β in Equation (4) shows an example, but a function (k ₀ , ₁ is a coefficient) similar to the effect of actual ambient light such as 1 / (1 + k ₀ xD + k ₁ xD ² ) is set. You can also.

The means for interpolating the luminance between the two patterns described in 1) is different from the mip mapping method of texture mapping that is generally performed. The mipmap prepares multiple patterns of the same size but with the same size, selects two optimal sizes for the scaling of the object, and interpolates between them using the scaling ratio to improve the image quality. It is a guarantee. In the present invention, instead of interpolating between patterns having different sizes as in a mipmap, different patterns of video are prepared and interpolated using distances from a light source (cube surface).

  Each of the means of the present invention generates a specular reflection component whose mapping position changes depending on the line-of-sight direction, but the present invention also implements a means for obtaining a reflection component that does not depend on the line-of-sight. As a means for this, the present invention defines a plurality of reference points and the luminance at each reference point on the cube 6 surface. In the second pass, the

The interpolated point is converted into a cube plane coordinate system by the same processing as in Fig. 6, and is compared with Zd of each CSPB of the cube 6 plane. If the interpolation point Zl is far from the CSPB Zd value, it is considered that there is no influence from the cube surface, and if it is close to the cube surface, the reference point luminance Li and the reference point Using the distance (S _i −P ₀ ) from S _i to the interpolation point P ₀ , the luminance at the interpolation point is determined from the relationship of equation (5). Here, the function D is a first-order or second-order attenuation function of the distance, which is generally inversely proportional to the distance. Multiplication of the luminance Li and the attenuation function D is performed on all six reference points (for i points), and the multiplication results are added and mapped to the interpolation point as diffused light Id in the cube space. Here, the reference point coordinate value S _i and the luminance L _i are stored in advance in a register or the like, and when the interpolation point P ₀ is obtained, the reference point coordinate value is read from this register and the distance between the two points is calculated. Ask.

  The depth value stored in CSPB is drawn with the axis perpendicular to the center of the cube plane as the projection center, so the silhouette boundary of the shading object around the line connecting each reference point and the interpolation point is accurate. Cannot judge. However, since what is being sought is the surface brightness of the cube surface, it is not necessary to strictly determine the polygon boundary of the light shielding object.

  In the present invention

As with the ambient light sneaking process defined in (5), when there is a light-shielding object, not only a means for masking the brightness of the surface but also the formula (5) above is multiplied by the distance scale function value as to the brightness from the reference point. Then, it is set as the luminance of the interpolation point.

  In the present invention, the processing with a large load is the generation of cubes and shadow polygons in the first pass. However, if geometric changes do not occur frequently in each object in the cube, the calculation of the shadow polygon need only be performed when the object changes. With this method, the first pass does not necessarily become a major obstacle to real-time drawing in a normal scene. Furthermore, in the present invention, when the objects in the cube space are small relative to the size of the cube space, the influence of the ambient light is stronger than the direct influence of the light-shielding object. It is also possible to select a method that omits. Thus, in the first pass, it is possible to increase the speed by performing selective processing according to the object shape.

  Regarding the process of obtaining the distance from the interpolation point to the cube reference point by the number of reference points for each interpolation point, in the present invention, each irradiation light obtained from the distance connecting the vertex and the reference point and the reference point luminance is previously set. It is possible to select a means for directly obtaining reflected light at the interpolation point by linearly interpolating the irradiation light inside the polygon. Six irradiation lights obtained for each cube surface are defined for each vertex. Interpolated irradiation light is applied to each cue surface.

The means for determining whether or not there is a light-shielding object is masked on the surface with the light-shielding object, and is added for each surface on the surface without the light-shielding object. It is also possible to define only one irradiation light component that is the sum of the irradiation light from all surfaces, not the six irradiation light at the apex, based on the size of the object in the cube space (the object is smaller than the space) May be small). In this case, the determination by the light shielding object is not performed. In the present invention, any of the above methods can be selectively applied from the relationship between the realism of the video and the real time property.

  As described above, in the present invention, one ambient light cube is defined in the scene, the luminance distribution of the environment space is patterned and stored on each surface, and the object in the cube space projected on each surface of the cube. Means for storing the distance from the projection plane in the cube / shadow polygon buffer through hidden surface elimination processing, and for each of the polygon vertices defining the object in the second pass, vertex coordinate values, normals, line-of-sight vectors, etc. A line-of-sight reflection vector is obtained from the normal and line-of-sight vector at a point inside the polygon by interpolation interpolation of the polygon, and the surface intersecting the cube is determined from the interpolation point and the line-of-sight reflection vector, and on the cube plane A means for determining the brightness of the point at the point, and the coordinate value in the polygon obtained by polygon interpolation in the second pass is changed to a predetermined cube plane coordinate system. Then, the distance from the light source stored in the cube / shadow polygon buffer is read, and the read distance is compared with the converted distance. The interpolation point is obstructed by a light-shielding object, masking the luminance from the cube surface, and if near, means for mapping the luminance from the corresponding surface, and the luminance of the interpolation point is the polygon The ambient light is mapped to each of the objects by using respective means for combining the luminance of the polygon itself and the luminance read from the cube surface by using a preset combination coefficient. In the present invention, a brightness pattern distributed on the cube plane is prepared in a clear pattern and a pattern blurred by a filter or the like, and the two patterns are interpolated using the distance between the interpolation point and the cube plane. The luminance obtained in this way is used as the luminance read from the cube memory, and the surface irradiation light that the luminance of the cube surface exerts on the interpolation point defines one or more reference points on the cube 6 surface. The reference point brightness is set for each point, and the distance to the interpolation point and the distance to each reference point are used to determine the brightness on the interpolation point, and further compared with the cube shadow polygon buffer depth value. Then, the means for selecting the irradiation light component from the surface of the cube 6 and the irradiation light component taking into account the distance from the reference point are defined as vertex variables in advance at the vertices of the polygon, and this is directly interpolated and interpolated. Determining the luminance of the interpolation point, it is to map the ambient light on the object with the respective means.

  The hexahedron defined in the present invention is described with the same name in order to correspond to the environment cube defined by a general environment mapping method. However, the hexahedron defined in the present invention is not limited to the rectangular parallelepiped including the cube.

Applicable to all means described in.
From the above, by the means of the present invention, not only the local light emitted from the ceiling or window, but also the global light is applied to the object surface included in the scene, including the spatial and geometrical relationship due to the light shielding object. Can be drawn as ambient light.

  According to the present invention, it is possible to draw an image having a light reflection effect with a realistic feeling close to nature in real time.

  The technique of the present invention is implemented in an LSI, a programmable logic circuit or the like or in the form of IP (Intelligent Property), and is applied to a computer graphics processor.

An embodiment of the ambient light mapping circuit of the present invention is shown in FIG. In the polygon rendering method, the shape of an object is expressed by an aggregate of polygons (polygons, mainly triangles). First, an ambient light cube is defined in the drawing space, and a cube memory 14 corresponding to each of the six cube faces is provided. In this memory 14, a light source distribution pattern (brightness) obtained by projecting light sources inside and outside the drawing space onto the face is provided. ) In advance. Here, the ambient light cube is assumed to have a rectangular parallelepiped shape including a cube. In the first pass (pass route of Pass 1 in FIG. 1), all polygons in the space are drawn with their cube planes as projection planes, and the distance (depth value) from the projection plane to the polygon interpolation point is cube-shadow polygon Store in the buffer (CSPB) 15. In the conventional environment cube, the projection center is set as the center point in the cube. On the contrary, in the CSPB of the present invention, the projection center is placed on the axis perpendicular to the center of each surface outside the cube. In the second pass, the vertex coordinates of the viewpoint coordinate system, the surface normal, the line-of-sight vector, etc. are defined for the vertices of the polygon, and these vertex variables are linearly interpolated by the polygon interpolation circuit 10, and the polygon interior Find the vertex definition variables at each point. Among these, the surface normal N, the line-of-sight vector V, and the coordinate value P ₀ are respectively added to the reflection vector calculation circuit 11,

The line-of-sight reflection vector R is obtained based on the equation (1). In addition, the cube plane intersection calculation circuit 12 calculates the intersection cube plane F (5 ≧ F ≧ 0) and the intersection (U, V) in the plane from the coordinate values P ₀ and R by the sign of the vector R,

The luminance Ic is read from the corresponding cube memory 14 using F and (U, V). On the other hand, the coordinate value P ₀ obtained by the polygon interpolation circuit 10 is converted from the viewpoint system coordinate value to the cube surface coordinate value (Xl, Yl, Zl) by the cube surface coordinate conversion circuit 13, and the corresponding CSPB (described above) is converted. The depth value Zd is read out from CSPB 15 corresponding to the F plane. The depth value comparison circuit 16 compares Zd and Zl. When Zl is closer to the cube surface, the point P ₀ maps the luminance Ic of the cube intersection to the interpolation point, and when Zl is far away. , Ic is masked. When mapping the cube intersection Ic to the interpolation point, from the luminance Ib of the object (this luminance is specific to the object in consideration of shading and shadows) and the synthesis coefficient α defined as the surface characteristics of the object,

Based on the equation (3), the luminance synthesis circuit 17 performs synthesis. The synthesized luminance becomes the luminance of the interpolation point, that is, the line-of-sight reflection point.

  FIG. 2 shows an ambient light mapping circuit for obtaining luminance to be mapped to an object in consideration of the distance from the cube surface according to the present invention. In FIG. 2, a cube plane coordinate conversion circuit 20 and a cube memory 21 are the same circuits as 13 and 14 in FIG. 1, respectively. However, the cube memory 21 is composed of two memories having a luminance distribution pattern. In the second pass, the interpolation point of the polygon is converted into cube surface coordinates 僵 (Xl, Yl, Zl) by the cube surface coordinate conversion circuit 20 and the coordinate values (Xl, Yl) are given to the CSPB 22. The depth value Zd is read from the CSPB, and this value and Zl are determined by the depth value comparison circuit 23 to determine the presence or absence of a light shielding object. The determination value ON is given to the luminance synthesis circuit 25. The ON signal indicates the front-rear relationship between Zd and Zl. The luminances Ic0 and Ic1 from 1 and 2 of the cube memory 21 are

Based on the equation (4), the luminance distribution pattern interpolation circuit 24 obtains the interpolated luminance Ic. D in equation (4) is Zl in FIG. From each of the interpolated luminance Ic, the object luminance Ib, and the object synthesis coefficient α, the luminance synthesis circuit

Based on the equation (3), the luminance of the interpolation point of the object is determined.

In the above embodiments, the mapping to the interpolation point handled the specular reflection related to the line-of-sight vector, but there is irradiation light whose cube plane luminance affects the interpolation point independently of the line-of-sight direction. . The ambient light is centered on this irradiated light component. FIG. 3 shows the reference points for obtaining the environmental cube and surface illumination of the present invention. In FIG. 3, the distances connecting the points S _i on the respective surfaces of the environment cube 30 and the interpolation point P ₀ of the object 31 are obtained, and the diffused light component is calculated from the luminance L _i on the cube surface based on the equation (5). Id is obtained. In FIG. 3, the reference point S _i on the cube surface is shown as one point per cube surface for convenience, but it is preferable to set a larger number of reference points in order to obtain surface luminance.

FIG. 4 shows the relationship with the interpolation point when there is a light-shielding object of the present invention. FIG. 4 shows the reference points S ₀ and S ₁ of the two surfaces 40 and 41 of the cube 6 surface, and shows the interpolation point P ₀ on the object 42 and between the cube surface 41 and the interpolation point P _0. The relationship between the positions of the light shielding objects 43 is shown in FIG. The presence / absence of the light shielding object is determined for each of the six surfaces. In FIG. 4, the case where the irradiation light component from the cube surface 41 is not added as being shielded and the depth value (distance from S ₁ to Q) of the light shielding object stored in the CSPB and the interpolation point P ₀ are formed. Using distance

The wraparound process can be selected by the distance scale function.

  FIG. 5 shows polygon vertex definition variables of the present invention. Using the distance from each cube surface to each polygon vertex and each reference point luminance, the luminance Ii0-5 (0-5 is the cube) in advance for each vertex C0-C2 of the polygon 50 (triangle in the figure). (Representing 6 planes) is calculated in advance, and these luminance values are defined together with other polygon vertex variables, and then the interpolation light is directly obtained to obtain the irradiation light at the interpolation point. In FIG. 5, a vertex coordinate value Pi (X, Y, Z) surface normal line Ni (Nx, Ny, Nz) and a line-of-sight vector Vi (Vx, Vy, Vz) are defined for the polygon vertex C0-C2. Any number i means vertex numbers 0-2). Pj represents an interpolation point. If the irradiation light component Ij0-5 at the interpolation point is obtained, the above-described surface is obtained for each surface.

The light-shielding object is determined, and it is determined whether or not to add. On the other hand, when a light-shielding object is not taken into account, a method of defining one luminance, which is the sum of all luminances from the six surfaces of Ii0-5, at each vertex is also possible.

  By mounting the circuit of the present invention as an IP (Intelligent Property) or a graphics processor LSI chip, real-time drawing can be performed in a system such as video production or CG game.

“Ambient light mapping circuit of the present invention is shown.” “Ambient light distribution interpolation circuit of the present invention is shown.” “The diffused light definition diagram from the cube surface of the present invention is shown.” “The relationship between the light shielding object of the present invention and the surface luminance is shown.” “Shows polygon vertex definition variables of the present invention.”

Explanation of symbols

FIG.
DESCRIPTION OF SYMBOLS 10 Polygon interpolation circuit 11 Reflection vector calculation circuit 12 Cube surface intersection calculation circuit 13 Cube surface coordinate conversion circuit 14 Cube memory 15 Cube shadow polygon buffer 16 Depth comparison circuit 17 Luminance synthesis circuit FIG.
DESCRIPTION OF SYMBOLS 20 Light source coordinate system conversion circuit 21 Cube memory 22 Cube shadow polygon buffer 23 Depth value comparison circuit 24 Light source distribution pattern interpolation circuit 25 Luminance synthesis circuit FIG.
30 Cube 31 Rendering object figure 4
40 Cube Surface 41 Cube Surface 42 Rendering Object 43 Shading Object Figure 5
50 Triangular vertex running variable

Claims (8)

  A computer graphics rendering circuit for obtaining reflected light of an object by irradiation of ambient light. An environment cube consisting of six faces including a rectangular parallelepiped is defined in a region surrounding a drawing space, and the cube corresponding to each face of the environment cube. A memory is provided, and the cube memory stores means for storing light source luminances projected on the respective surfaces that irradiate the space in the cube, and the objects in the cube space are hidden surfaces by using the respective cube surfaces as projection surfaces. Means for providing a cube / shadow polygon buffer for storing the distance between the object and the cube surface using an erasure method; and at least vertex coordinate values, surface normals and line-of-sight vectors for each vertex of the polygon representing the object And define the vertex definition value linearly in the polygon, and the normal at each polygon interpolation point. A line-of-sight vector from the line-of-sight vector, a cube plane and a coordinate point where the line-of-sight reflection vector intersects the cube plane, and means for reading the luminance stored in the cube memory; and the polygon interpolation point coordinates The value is converted into the projected coordinate system of the surface where the line-of-sight reflection vector intersects, and the cube / shadow polygon buffer corresponding to the corresponding surface is selected and stored in the cube / shadow polygon buffer from the converted coordinate value. If the depth value is farther than the distance of the cube / shadow polygon buffer, this distance is compared with the distance from the projection plane of the converted coordinate value (hereinafter referred to as the depth value). The interpolation point of the polygon is read from the cube memory assuming that it is obstructed by the light shielding object. On the other hand, means having a means for mapping to the interpolation point when it is close, and the rendering luminance of the interpolation point is a luminance set in advance for the object itself with the luminance of the polygon itself and the luminance of the light source distribution pattern. An ambient light mapping circuit that determines ambient light on the surface of an object with each means for linearly synthesizing using a synthesis coefficient.   2. The circuit according to claim 1, wherein when there is a light-shielding object between a polygon interpolation point and a cube surface where the line-of-sight reflection vector intersects, means for obtaining a distance between the interpolation point and the light-shielding object, and this distance is zero. The distance scale function is defined as the minimum value as it approaches and the maximum value as it moves away, and the function value is multiplied by the readout luminance from the cube memory that is the intersection plane, and the resulting luminance is the luminance from the intersection plane. Ambient light mapping circuit.   2. The circuit according to claim 1, wherein a brightness distribution pattern stored in the cube memory is provided with a sharp distribution shape, means for preparing two patterns obtained by filtering the distribution shape by filtering, a polygon interpolation point, and the line-of-sight reflection vector. An ambient light mapping circuit having respective means for regarding a luminance obtained by interpolating between the two patterns as a luminance of a corresponding cube surface by using a distance formed between intersecting cube surfaces.   2. The circuit according to claim 1, wherein one or more reference points are defined on each of the six surfaces of the cube with respect to the surface reflected light that the photon distribution pattern luminance of each cube surface exerts on the interpolation point. Each distance attenuation function value using the distance to the variable as a variable, and means for adding the value obtained by multiplying the function value by the luminance of the reference point of each corresponding surface for each cube surface; and As a means for determining whether or not the interpolation point is affected, the result of the presence / absence determination of the light shielding object according to claim 1 is performed on each cube surface, and if there is a light shielding object, the corresponding cube surface In the case where there is no light-shielding object, the ambient light mapping circuit that accumulates the addition value of each corresponding surface for each surface and uses this accumulated value as the surface luminance from the cube surface of the interpolation point is masked. .   5. The circuit according to claim 1, wherein a value obtained by multiplying a distance attenuation function value and luminance for each reference point is summed for each cube surface, and the sum value is defined as a vertex variable at a polygon vertex and interpolated. An ambient light mapping circuit that obtains surface brightness for each cube surface.   5. The circuit according to claim 1 or 4, wherein a value obtained by multiplying a distance attenuation function value and luminance for each reference point is added for all six planes, and the added value is defined as a vertex variable at a polygon vertex and interpolated directly. Ambient light mapping circuit that obtains surface brightness from all cube surfaces. 6. The circuit according to claim 1, 2 and 5, wherein a value obtained by multiplying the interpolated point luminance of the reference point added luminance for each cube plane obtained in claim 5 by the distance scale function value of claim 2 is calculated for each cube plane. Ambient light mapping circuit for surface brightness.   A computer graphics image device using the ambient light mapping circuit according to claim 1.

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