JP2000207576A - Method and device for processing image and recording medium recording image processing program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize rendering by voxel division by which aliasing does not occur with a small amount of required memory capacity in an image processing using a rendering method such as rate racing. SOLUTION: The three axes of a three-dimensional space V to be a display object are adopted as an X-axis, a Y-axis and a Z-axis with a viewpoint as an original point and a screen S or displaying is vertically positioned as against the Z-axis. When it is assumed, the three-dimensional space V is divided into D (a certain integer) in parallel with a screen plane. Besides, it is divided by a plane passing the view point and the boundary of a pixel on the screen S to generate truncated pyramids. The truncated pyramids are assigned to a three-dimensional arrayal memory M, the intersection point of a light beam from the viewpoint with an object is located on the memory M and intersection is judged.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for calculating intersections of rendering techniques such as ray tracing and the like, and to an image processing technique using the processing, which is used in a three-dimensional rendering system.

[0002]

2. Description of the Related Art As a rendering technique for creating a three-dimensional image, there is a ray tracing method. FIG. 7 is a diagram for explaining a ray tracing method. In the ray tracing method, as shown in FIG. 7, a ray passing from a viewpoint to a pixel on a screen is generated, and rendering is performed by examining intersections of all objects. In this method, there is a problem that the number of times of intersection determination between the object and the light beam becomes enormous, and the processing time becomes long. As a method of reducing the processing time, as shown in FIG. 8, a method of dividing a three-dimensional space into small cubes (voxels) and associating them with a memory space in which a three-dimensional array is defined, and performing intersection determination. is there. If all the objects are written in the memory and the memory space is searched along the light rays, the processing time required for the intersection determination can be reduced.

However, in this conventional voxel division method, a ray does not always pass through the center of a voxel, and there is a problem that aliasing occurs and image quality deteriorates.
FIG. 9 is a diagram for explaining the problem that the image quality is deteriorated, and is a diagram showing a conventional voxel dividing method viewed from the YZ plane. As shown in FIG. 9, a ray 1 passing from the viewpoint to the center of the pixel of the screen S intersects with the voxel A, and rendering is performed using the data of the voxel A. However, the drawing data of voxel A and voxel B are actually continuous, and the actual drawing data of the intersection with ray 1 is the data between voxel A and voxel B. Become. As a method of avoiding this, there is a method of calculating a plurality of light rays such as the light rays 2 and the light rays 3 and performing rendering. According to this method, the image quality is improved, but there is a problem that the processing time becomes longer.

In the above method, the further away from the viewpoint, the greater the number of voxels in the X-axis direction and the Y-axis direction. For this reason, there is a problem that the memory capacity for defining the required three-dimensional array also increases.

[0005]

As described above, the ray tracing method using voxels can reduce the amount of arithmetic processing, but causes aliasing to degrade the image quality.
The memory capacity required for processing is also large. An object of the present invention is to realize a rendering by a voxel division method which requires a small memory capacity and does not cause aliasing.

[0006]

SUMMARY OF THE INVENTION The present invention relates to an image processing using a rendering technique such as ray tracing.
Assume that the viewpoint is the origin, the three axes of the three-dimensional space V to be displayed are the X axis, the Y axis, the Z axis, and the screen S to be displayed is perpendicular to the Z axis of the three-dimensional space V. It is divided into an integer D parallel to the screen plane, and further divided by a plane passing through the viewpoint and passing through the boundary of the pixel of the screen to generate a truncated pyramid. This is an image processing method in which an intersection of a light ray from a viewpoint and an object is searched in the memory M to determine an intersection.

According to the present invention, in a rendering technique such as ray tracing, a ray passing from the viewpoint to the center of a pixel on the screen is divided so that the ray always passes through the center of a voxel, and the intersection of the polygon to be displayed and the ray is determined. Since determination and drawing are performed, aliasing does not occur and an image with little distortion can be generated at high speed. In addition, the number of voxels in the X-axis and Y-axis directions is equal to the number of pixels on the screen even at a location far from the viewpoint, so that the memory capacity required for processing can be reduced.

[0008]

[First Embodiment] FIG. 1 shows an example of an image processing method according to the first embodiment. In image processing using a rendering technique such as ray tracing, the viewpoint is set as the origin, the three axes of the three-dimensional space V to be displayed are the X axis, the Y axis, the Z axis, and the screen S to be displayed is the Z axis of the three-dimensional space V. Suppose it is perpendicular to the axis.

As shown in FIG. 1A, a three-dimensional space V is divided into a certain number D of integers parallel to the screen S, and further divided by a plane passing through the viewpoint and passing through the boundaries of the pixels of the screen S. Generate a truncated quadrangular pyramid. These quadrangular truncated pyramids are respectively allocated to memories M defining a three-dimensional array as shown in FIG. Then, the memory M is used for determining the intersection between the light ray from the viewpoint and the object in the three-dimensional space V, which is performed in processing such as ray tracing. Since all the objects to be displayed in the three-dimensional space V are developed on the memory M, if the memory M is searched along the rays,
The intersection with the object in the three-dimensional space V can be determined at high speed.

The three-dimensional space V is divided by a plane passing through the boundary between the viewpoint and the pixels of the screen S to form voxels. Therefore, if the three-dimensional space V to be displayed is voxelized by the present method, the screen S can be viewed from the viewpoint.
A ray passing through the center of the pixel passes through the center of the voxel.

FIG. 2 shows an example of division into voxels by the present voxel conversion method viewed from the YZ plane. As is clear from FIG. 2, it can be seen that the light ray passing through the center of the screen passes through the center of the voxel. As described above, since the light beam passes through the center of the voxel, aliasing does not occur even if rendering is performed only with information on the voxel that intersects the light beam. In the conventional method based on voxel division, it was necessary to search a plurality of optical paths to obtain a high-quality image.
By searching for two optical paths, a high-quality image can be obtained.

[Embodiment 2] FIG. 3 shows an example of an image processing method according to the second embodiment. In FIG. 3, the three-dimensional space V
The minimum value of the Z axis is z _s , the maximum value is z _l ,
Assuming that an integer up to 1 is n,

[0013]

(Equation 1)

FIG. 2 shows a state viewed from the YZ plane when divided by a plane that satisfies.

FIG. 4 is a view showing a voxel when the Z-axis direction is equally divided as viewed from the YZ plane. As in FIG. 4, the memory M is divided equally from z _s in D number in the section z _l
, The path of the reflected light and the like in the three-dimensional space V becomes a curve in the memory M, and the optical path calculation becomes complicated. On the other hand, when the data is divided by a plane satisfying (Equation 1) as shown in FIG. 3, a straight line in the three-dimensional space V is also a straight line in the corresponding memory M.

Hereinafter, it will be proved that a straight line is obtained by using a mathematical expression.

The length of the X axis of the screen S is s _w , the number of pixels is p _w , the length of the Y axis is s _h , the number of pixels is _ph , and the distance from the viewpoint is L. One point v on
(X _v , y _v , z _v ) is one point m (x _m , y
_m , z _m ), the following relationship holds between v and m.

[0018]

(Equation 2)

Here, three points v in a three-dimensional space V
_{1 (x v1, y v1,} z v1), v 2 (x v2, y v2, z v2),
When v ₃ (x _v3 , y _v3 , z _v3 ) is on a straight line,

[0020]

(Equation 3)

The following holds. First, expanding the terms y and z,

[0022]

(Equation 4)

## EQU1 ## Substituting (Equation 2) for the terms y _v1 , y _v2 , y _v3 in (Equation 4) gives

[0024]

(Equation 5)

## EQU1 ## Substituting (Equation 2) into the terms of z _v1 , z _v2 , z _v3 in (Equation 5),

[0026]

(Equation 6)

Is obtained. Similarly, when calculating with respect to x and z in (Equation 3),

[0028]

(Equation 7)

It can be seen that the straight line is maintained even if the straight line in the three-dimensional space V is converted into coordinates on the memory M using (Equation 2).

Therefore, if the present conversion technique is used, the intersection between the reflected light, the refracted light and the like and the object can be determined using the straight line on the memory M, and the determination can be made at high speed.

[Embodiment 3] FIG. 5 is a processing flowchart for realizing a rendering method using the voxel conversion method according to the third aspect.

First, geometry processing (conversion to the camera coordinate system) of the polygon P to be displayed is performed (step S1), and one or a plurality of polygons P defined in the three-dimensional camera coordinate system to be displayed are processed. The vertices are converted to the coordinate system of the memory M in which the three-dimensional array is defined by using the above (Equation 2) (Step S2). The drawing information of the polygon P is written to the coordinates of the memory M corresponding to the outer periphery and the inner surface of the polygon P expressed by the coordinate system of the memory M (step S3). When all polygons have been written into the memory (step S
4) Perform drawing processing by ray tracing.

A ray for each pixel on the screen S
As the initial setting of the tracing process,
Let the coordinates of one pixel c be (x_c, Y_c) And memory coordinates
(X _c, Y_c, 0) to the starting point E of the ray, (0, 0, 1)
Is the direction vector V of the light ray (step S5). Pic
The color information of the cell c is the direction vector V of the ray from the viewpoint.
Is searched in the memory space based on the polygon P to be displayed.
Is obtained (steps S6 to S7). And that
Calculates color information based on the drawing information of polygon P at the intersection of
Then, writing to the screen is performed (step S8).
In some cases, the reflected or refracted light from the intersection is also calculated.
(Steps S9 to S1)
2). For all pixels in the screen,
Do the same calculation until the clean drawing is completed.
(Step S13), a three-dimensional image can be generated.
Wear.

[Embodiment 4] FIG. 6 is a diagram showing an example of a block configuration of an image processing apparatus according to a fourth aspect. This apparatus comprises a polygon information writing circuit 10, a three-dimensional array memory 20 defining a three-dimensional array, a ray tracing processing circuit 3,
Consists of zero.

The polygon information writing circuit 10 converts the vertex information of the polygon into a memory coordinate system in accordance with the above (Equation 2), calculates the memory coordinates in the given polygon, and And writes the drawing information of the polygon into the three-dimensional array memory 20. The coordinate conversion circuit 11 is composed of four arithmetic operators, and the drawing area calculation circuit 12 can be realized by using a scan line method or the like.

When the writing into the three-dimensional array memory 20 is completed, a three-dimensional image is generated by the ray tracing method from the information in the three-dimensional array memory 20 by the ray tracing processing circuit 30 and written into the video memory 40. The ray tracing processing circuit 30 includes an optical path operation circuit 31
, A memory address along the optical path is generated, and the intersection determination circuit 32 determines whether there is a polygon on the light beam. If they intersect, the color data calculation circuit 33 calculates the color data to be written to the video memory 40 based on the drawing information in the three-dimensional array memory 20. Further, based on the data of the reflectance and the refractive index at the intersection, the reflected light / refractive light arithmetic circuit 34 is used.
To obtain a light vector and give it to the light path operation circuit 31.
Similarly, color data of reflected light and refracted light is obtained. Note that these arithmetic circuits can be realized by an integrated circuit or the like in which logic circuits are combined.

A general-purpose CPU or DSP (Digital Si
These processes can be performed by a computer such as a gnal processor. Programs for performing these processes can be stored in an appropriate recording medium such as a computer-readable portable medium memory, semiconductor memory, or hard disk.

[0038]

As described above, by using the present invention, in a rendering method such as ray tracing, a ray passing from the viewpoint to the center of a pixel on the screen is divided so as to always pass through the center of a voxel. , To determine the intersection between the polygon to be displayed and the ray,
Aliasing does not occur, and an image with little distortion can be generated at high speed. In addition, the number of voxels in the X-axis and Y-axis directions is equal to the number of pixels on the screen even at a location far from the viewpoint, so that the memory capacity required for processing can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram for describing a first embodiment of an image processing method.

FIG. 2 is a diagram illustrating a voxel conversion method according to the first embodiment as viewed from a YZ plane.

FIG. 3 is a diagram for explaining a second embodiment of the image processing method.

FIG. 4 shows a voxel obtained by equally dividing the Z-axis direction into Y.
It is the figure seen from the Z plane.

FIG. 5 is a processing flowchart for realizing a rendering method using a voxel conversion method according to the third embodiment.

FIG. 6 is a diagram illustrating an example of a block configuration of an image processing apparatus.

FIG. 7 is an explanatory diagram of a ray tracing technique.

FIG. 8 is a diagram showing a conventional voxel division technique.

FIG. 9 is a diagram showing a conventional voxel dividing method viewed from the YZ plane.

[Explanation of symbols]

S of the X-axis of the integer s _w screen with the distance D between the screen V 3 dimensional space memory L viewpoint and the screen that defines the M 3-dimensional array of length s _h Screen Y-axis length p _w Screen X-axis direction the maximum value of the minimum values z _l Z-axis of the number z _s Z-axis of the number p _h screen Y-axis direction of the pixels of the pixel

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Hitoshi Kitazawa 3-19-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo F-term in Nippon Telegraph and Telephone Corporation (reference) 5B050 BA04 BA09 BA10 EA27 EA28 FA06 5B080 BA03 BA04 BA05 CA08 GA06

Claims (9)

[Claims] In an image processing method using a rendering technique such as ray tracing, a viewpoint is set as an origin, and three axes of a three-dimensional space V to be displayed are X-axis, Y-axis, and Z-axis.
It is assumed that the axis and the screen S to be displayed are perpendicular to the Z axis of the three-dimensional space V, and the three-dimensional space V is parallel to the screen plane.
A memory M that divides into a certain integer D and further generates a truncated quadrangular pyramid by dividing by a plane passing through the viewpoint and passing through the boundary of the pixel of the screen S, and defining these truncated pyramids in a three-dimensional array
An image processing method for searching for an intersection between a light ray from a viewpoint and an object in the memory M and performing intersection determination. 2. The image processing method according to claim 1, wherein
When the minimum value of the Z axis of the three-dimensional space V is z _s , the maximum value is z _l, and an integer from 1 to (D−1) is n, the three-dimensional space V is represented by the following equation: z = z _s ÷ image processing method characterized by dividing by _{(1- (1-z s ÷} z l) ÷ D × n) plane satisfying. 3. The image processing method according to claim 1, wherein a length of the X axis of the screen S is s _w , a number of pixels is p _w , a length of the Y axis is s _h , and a number of pixels is To p
_h, and the distance between the viewpoint is L, one defined by three-dimensional camera coordinate system to be displayed or a plurality of vertices of the polygon _{P (x v, y v,} z v) and the following equation x _{m = p w ÷ s w × L} × x v ÷ z v y m = p h ÷ s h × L × y v ÷ z v z m = (1-z s ÷ z v) ÷ (1-z s ÷ z _l ) × D (where x _m , y _m , and z _m are converted to integers).
The coordinates (x _m , y _m ,
z _m ), the drawing information of the polygon P is written on the outer periphery and the inner surface of the polygon P in the coordinate system of the memory M obtained by the conversion into the coordinates (x _C , y _C ) of an arbitrary pixel c on the screen S. Of the drawing data at the memory coordinates (x _C , y _C , 0) and the direction vector (0, 0,
1) is searched in the memory space as a ray from the viewpoint, the intersection with the polygon P to be displayed is obtained, the color data of the pixel is obtained, and the calculation is similarly performed for all the pixels in the screen S. An image processing method for generating a three-dimensional image. 4. An image processing apparatus comprising a memory writing circuit, a memory, and a ray tracing circuit for generating a three-dimensional image to be displayed on a screen plane, wherein the memory writing circuit has a screen plane perpendicular to the Z axis. As described above, the XYZ coordinate system of the three-dimensional space V to be displayed is taken, the three-dimensional space V is divided by D planes (D is an integer) parallel to the screen plane, and further passes through the boundary between the viewpoint and the screen pixel. Generate a truncated quadrangular pyramid by dividing the plane
A drawing area calculation circuit for allocating the truncated pyramids to the memory defining a three-dimensional array, wherein the ray tracing circuit searches the memory for an intersection between a light ray from a viewpoint and an object to be displayed, and determines an intersection. An image processing apparatus comprising an intersection determination circuit for performing 5. The image processing apparatus according to claim 4, wherein
When the minimum value of the Z coordinate value of the three-dimensional space V is z _s , the maximum value is z _l, and an integer from 1 to D−1 is n, the drawing area calculation circuit converts the three-dimensional space V into following formula z = z _s ÷ image processing apparatus, characterized in that the split _{(1- (1-z s ÷} z l) ÷ D × n) D number of planes satisfying. 6. The image processing according to claim 4 or claim 5.
In the apparatus, the X in the three-dimensional space V is set with the viewpoint as the origin
Take the YZ coordinate system and set the length of the X axis of the screen to s_w, Pi
The number of cells_w, Y axis length is s_h, The number of pixels
p_h, When the distance from the viewpoint is L,
The circuit is composed of points (x_v, Y_v, Z_v)
Is given by x_m= P_w÷ s_w× Lxx_v÷ z_v y_m= P_h÷ s_h× L × y_v÷ z_v z_m= (1-z_s÷ z_v) ÷ (1-z_s÷ z_l) × D (where x_m, Y_m, Z_mIs converted to an integer).
Memory coordinate system (x_m, Y_m, Z
_m) And one of the display objects
Is based on the coordinate transformation results for the vertices of the polygon P
And the outer and inner surfaces of the polygon P in the memory coordinate system
Drawing area calculation circuit for writing the drawing data of polygon P to
And the ray tracing circuit comprises a screen
One pixel (x_C, Y_C) Optical path against memory
Mark (x _C, Y_C, 0) as the starting point and the direction vector (0, 0,
The optical path arithmetic circuit calculated as 1) and the calculated optical path
Therefore, the memory is searched, and the intersection with the polygon P to be displayed is obtained.
Intersection calculation circuit for calculating the intersection, and the calculated intersection and memory
Color for calculating the color data of the pixel from the drawing information of
Image processing apparatus, comprising: a color data calculation circuit.
Place. 7. A recording medium in which a program for performing image processing using a rendering technique such as ray tracing by a computer is recorded, wherein a viewpoint is set as an origin, and three axes of a three-dimensional space V to be displayed are set as X. It is assumed that the axis S, the Y axis, the Z axis, and the screen S to be displayed are perpendicular to the Z axis of the three-dimensional space V, and the three-dimensional space V is divided into an integer D parallel to the plane of the screen S. A quadrangular truncated pyramid is generated by dividing by a plane passing through the boundary of the pixel of S, and these quadrangular truncated pyramids are respectively allocated to a memory M defining a three-dimensional array, and an intersection of a light ray from a viewpoint and an object on the memory M A recording medium on which an image processing program is recorded, wherein a program for causing a computer to execute a process of searching for and determining an intersection is recorded. 8. A recording medium on which the image processing program according to claim 7 is recorded, wherein the image processing program comprises:
When the minimum value of the Z axis of the three-dimensional space V is z _s , the maximum value is z _l, and an integer from 1 to (D−1) is n, the three-dimensional space V is represented by the following equation: z = z _s ÷ processing for dividing a plane satisfying _{(1- (1-z s ÷} z l) ÷ D × n), the recording medium recording an image processing program characterized by including a program to be executed by the computer. 9. A recording medium on which the image processing program according to claim 7 or 8 is recorded, wherein said image processing program sets the length of the X axis of the screen S to s _w , and the number of pixels to p _w , Y the length of the shaft s _h, the number of pixels p
_h, and the distance between the viewpoint is L, one defined by three-dimensional camera coordinate system to be displayed or a plurality of vertices of the polygon _{P (x v, y v,} z v) and the following equation x _{m = p w ÷ s w × L} × x v ÷ z v y m = p h ÷ s h × L × y v ÷ z v z m = (1-z s ÷ z v) ÷ (1-z s ÷ z _l ) × D (where x _m , y _m , z _m are converted to integers)
Coordinates (x _m , y _m , z) of the memory M defining the three-dimensional array
_m ), the drawing information of the polygon P is written on the outer and inner surfaces of the polygon P in the coordinate system of the memory M obtained by the conversion into the coordinates (x _C , y _C ) of an arbitrary pixel c on the screen S. The drawing data is stored in memory coordinates (x _C ,
y _C , 0) as a starting point, and a direction vector (0, 0, 1) as a light ray from a viewpoint, search in the memory space, find an intersection with a polygon P to be displayed, and obtain color data of a pixel,
A recording medium storing an image processing program characterized by including a program for causing a computer to execute a process of generating a three-dimensional image by similarly calculating all pixels in the screen S.