JPH06301792A - Texture mapping device - Google Patents

Abstract

(57) [Summary] [Structure] When a texture image is pasted on polygons forming an object to be displayed as an image, the screen of each vertex of the polygon obtained by the screen coordinate calculation function unit 21 in the graphic processor 16 is displayed. The polygon division number determination function unit 22 determines the number of divisions based on the coordinates, the polygon division function unit 23 divides the polygons, and the texture mapping function unit 24 performs texture mapping for each of these divided small polygons. To do. [Effect] It is possible to effectively prevent the image quality deterioration on the diagonal line of the polygon without increasing the calculation amount.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a texture mapping device for creating an image using a texture mapping technique in a graphic computer, a special effect device, a video game machine or the like which is a video device using a computer. is there.

[0002]

2. Description of the Related Art For example, in a home TV game machine, a personal computer device, a graphic computer device, or the like, image data (display output) output and displayed on a television receiver, a monitor receiver, a CRT display device, or the like. So-called textures (fabric, ground pattern) when generating or creating image data)
A texture mapping method may be adopted in which the image is attached to a desired surface such as a polyhedron to be displayed (a polygonal area that is a unit forming an object to be displayed as an image, a so-called polygon).

FIG. 6 is a block diagram showing an example of the configuration of a conventional image creating apparatus having a texture mapping function. In FIG. 6, a CPU 101 including a microprocessor is connected to a bus line 109,
The bus line 109 includes a main memory 102 for storing programs and data, a video memory 103 for storing data of an image (texture source image) which is a source of the texture, and a display output image generated or created. Video memory 104 in which data is stored
Is at least connected. The CPU 101 reads the data of the texture source image from the video memory 103, modifies it as necessary, and adds it to the video memory 104.
Write in. The data of the display output image written in the display area of the video memory 104 is the D / A converter 10.
At 5, it is converted into an analog signal and taken out as a video output.

When a texture mapping process is performed using the image forming apparatus having the structure shown in FIG. 6, any one so-called polygon (a polygonal area which is a unit forming an object to be displayed as an image) is used. When a predetermined texture image is to be attached to, the following method is used, for example. This method will be described with reference to the flowchart of FIG.

In FIG. 7, the three-dimensional coordinates (local coordinate system) of each vertex of a polygon, for example, three vertices of a triangle are multiplied by a coordinate conversion matrix (step S9).
1) and the translation vector addition (step S92)
3 in a fixed coordinate system on the screen for display
Find the dimensional coordinates.

Next, the three-dimensional coordinates in the screen coordinate system are perspective-transformed (step S93), and the screen (display surface) is displayed.
Find the two-dimensional coordinates above.

As described above, since the correspondence between the texture image and the polygon on the screen at the three vertices of each triangle has been established, the primary conversion equation is created based on this (step S94).
be able to. Using this linear conversion formula, a point on the texture image corresponding to a pixel included in the polygon is obtained, and the pixel value is written to the pixel in the polygon (step S9).
5).

When texture mapping is performed on a polygon composed of a plurality of triangles by such a method, for example, when the polygon is a quadrangle, the quadrangle 81 is divided into two triangles 82 and 83 as shown in FIG. 8B. Then, the mapping operation is performed for each triangle 82, 83. 8A shows a corresponding quadrangle 81t and two divided triangles 82t and 83t on the texture image side, respectively.

FIG. 9 shows a quadrangle 8 on the texture image side when a lattice pattern (grid) is used as a concrete example of the texture.
1t and two division triangles 82t and 83t, and a quadrangle 81 on the display (screen) image side to which this is mapped
And two divided triangles 82 and 83, respectively.

Here, when the size of the polygon is large and distorted as compared with the parallelogram, in the texture mapping by the above-described method, for example, as shown in FIG. At that point, the refraction of the texture occurs and the quality of the displayed image is impaired.

Therefore, in order to prevent the deterioration of image quality due to such refraction of texture, a method shown in the flowchart of FIG. 10 has been considered.

That is, first, in step S71,
The polygon is divided into small polygons, which are some (for example, four) divided areas, as shown in FIG. 11B. In the next step S72, the texture image is also divided so as to correspond to each of the small polygons (A in FIG. 11).

After the next step S73, the processing from step S91 to step S95 in FIG. 7 is performed for each of the divided small polygons. That is, steps S73, S74, S75, S76, and S77 in FIG.
Steps S91, S92, S93, S9 in FIG. 7 described above.
4 and S95, respectively, the same processing is performed on the small polygon. In step S78, it is determined whether or not the processes of steps S91 to S95 have been performed for all the small polygons. If NO, the process returns to step S73, and if YES, the process is terminated, and the whole process is completed. Texture mapping is completed.

By performing the texture mapping process for each small polygon obtained by dividing such a polygon, the image distortion occurs only in each small polygon, and the deterioration of the image quality as a whole is reduced. Become.

In FIG. 12, the texture image side when a grid pattern (grid) is used as a concrete example of the texture is A.
Each of the rectangular polygons on the display (screen) image side to which this is mapped is shown in B. This FIG.
12 is compared with B of FIG. 9 above, the bending of the texture on the diagonal line of the polygon (quadrangle) is shown in FIG.
B is less (less noticeable)
I understand.

[0016]

By the way, the above-mentioned FIG.
According to the method described in (1), since the number of polygon vertices increases in proportion to the number of divisions, the total calculation amount also increases. That is, when a quadrangle is assumed as a polygon, and when texture mapping is applied to this quadrilateral polygon, (1) unless the polygon is subdivided, the image quality deteriorates on the diagonal line. (2) When the polygon is subdivided, the calculation amount increases by the number of divisions. (3) If the number of divisions is increased in advance, the calculation becomes useless when the polygons before division are small. There is a problem.

The present invention has been made in view of such a situation, and it is possible to effectively improve image quality deterioration such as bending of a texture on a diagonal of a polygon without significantly increasing the amount of calculation. An object of the present invention is to provide a simple texture mapping device.

[0018]

A texture mapping device according to the present invention is a texture mapping device for pasting a desired texture image onto a polygonal area (so-called polygon) which is a unit constituting an object to be image-displayed. , Means for determining the number of divisions of the polygonal area in accordance with information on the shape of the polygonal area obtained from the screen coordinates of the respective vertices of the polygonal area, and from the screen coordinates of the respective vertices of the polygonal area Means for dividing into a plurality of divided polygonal areas (so-called small polygons) by interpolation according to the number of divisions, and each divided polygonal area using the screen coordinates of each vertex of each divided polygonal area. Means for performing texture mapping of a region is provided to solve the above-mentioned problems.

Here, as the information on the above-mentioned shape,
The strain amount and / or area (size) of the polygonal region can be used.

[0020]

The deterioration of the image quality such as the refraction of the texture on the diagonal line of the polygon (unit polygon area) on the screen is improved by dividing the polygon, and the number of divisions at this time is adjusted by the distortion amount and area (largeness) of the polygon. Therefore, the necessary minimum division is performed, and it is possible to prevent an unnecessary increase in the calculation amount. Since the vertex coordinates of the small polygon (divided polygonal areas) in the screen coordinate system are interpolated from the vertex coordinates of the original polygon in the screen coordinate system, the vertex coordinates of each small polygon. Does not have to be obtained by coordinate conversion, and the increase in calculation amount is small.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block circuit diagram showing a schematic configuration of a main part of an embodiment of a texture mapping device according to the present invention.

In FIG. 1, a CPU 11 including a microprocessor or the like is connected to a bus line 19, and the bus line 19 includes a main memory 12 for storing programs and data and an input device 14 such as an input pad.
Interface 1 for importing operation data from
3 and a graphic processor 1 for generating an image
6 is connected, and a video memory 15 for storing the generated image is connected to the graphic processor 16. Here, in the main memory 12, not only the program, but also the three-dimensional vertex coordinates (local coordinates or object coordinates) of the object to be drawn, the coordinate conversion matrix, and the units forming each surface of the displayed object. Various information such as information indicating a storage location of a so-called texture image to be attached to the polygon area (so-called polygon) is stored. The CPU 11 takes out the information required according to the execution of the program stored in the main memory 12 from the main memory 12 and transfers it to the graphic processor 16.

The graphic processor 16 performs processing such as creation and drawing of an image to be displayed. Especially, regarding the main processing relating to texture mapping,
The function blocks will be described. These functional blocks represent each function realized by software as hardware.

The screen coordinate calculation function unit 21 uses a three-dimensional coordinate system (screen coordinate system) fixed on the screen based on the vertex coordinates (local coordinates) and coordinate conversion matrix of the object stored in the main memory 12. The coordinates are calculated, and the two-dimensional coordinates on the screen that are actually displayed are calculated.

The polygon division number determination function unit 22 responds to information regarding the shape of the polygon (unit polygon area), which is obtained from the screen coordinates of the vertices of the polygon.
The number of divisions of the polygon is determined. Specifically, when the polygon is a quadrangle, the number of divisions of the polygon is determined according to the “distortion” or “size (or area)” of the two-dimensional coordinate on the screen with four vertices. For example, the "distortion" increases as the shape deviates from the parallelogram. The "size" is the size (area) in the screen coordinate system, that is, the apparent size.

The polygon division function unit 23 divides the polygon into a plurality of division areas (small polygons) by interpolation from the screen coordinates of the vertices of the polygon according to the division number. In this case, the bisection point of the side may be determined by the average of both end points, and the center point of the polygon may be determined by the average of four vertices.

The texture mapping function unit 24 performs the texture mapping of each small polygon by using the screen coordinates of each vertex of each divided area (small polygon). Specifically, if the polygon is a quadrangle and the small polygon that divides it is also a quadrangle,
Triangulation is performed on each small polygon, a primary conversion formula is calculated for each triangle, and a point on the texture image corresponding to the pixel included in each small polygon is calculated using this linear conversion formula, and the pixel value is It suffices to write to the pixels in the small polygon.

Next, a specific example of the processing flow of the embodiment of the present invention will be described with reference to the flowchart of FIG. In this specific example, for simplification of description, it is assumed that, for example, a quadrangle is used as the polygon, which is a polygonal area serving as a unit constituent element of an object for image display.

The three-dimensional coordinates (local coordinate system) of the four vertices of a quadrangle, which is a specific example of the polygon described above, are multiplied by the coordinate conversion matrix in step S31, and the translation vector is added in step S32. By performing the above, three-dimensional coordinates in a coordinate system fixed on the screen (screen coordinate system) are obtained. In the next step S33, the three-dimensional coordinates in the screen coordinate system are perspective-transformed to obtain the two-dimensional coordinates on the screen.

In the next step S34, "strain" and "size (or area)" are obtained from the screen coordinates of the four vertices obtained in the above process, and at least these "strain" and "size" are obtained. According to one of them, the number of divisions of the quadrangle that is the polygon is determined. here,
FIG. 3 is a diagram for explaining the definitions of the above “strain” and “size”. As shown in FIGS. 3A and 3B, the “strain” increases as the shape deviates from the parallelogram. As shown in C and D of 3, the size of the “size” is determined by the apparent size (area) in the screen coordinate system. The number of divisions of the quadrangle is determined according to the magnitude of these “distortion” and “size”.

An example of an evaluation formula for determining the number of divisions according to the "distortion" and "size" will be described with reference to FIG. The four vertices of the polygon (quadrangle) shown in FIG. 4 are A, B, C, and D, and the vector of side AB is a and side A is
Let a vector b of D, a vector of a side DC be c, a vector d of a side BC, and mutually orthogonal x and y components of the vector a (a ₀ , a ₁ ), and each component of the vector b be (b ₀ , b ₁ ), and each component of the vector c is (c ₀ , c
₁ ) and each component of the vector d is (d ₀ , d ₁ ), the amount of “strain” (strain amount) H is H = (a ₀ −c ₀ ) ² + (a ₁ −c _{1 ^{) 2 + (b 0 -d 0}} ) 2 + (b 1 -d 1) 2 ··· (1) Further, the amount E representing the _{"size", E = | a 0 b 1} -a 1 b ₀ | + | c ₀ d ₁ −c ₁ d ₀ | It is defined as (2). Then, by using these values H and E, the division number D _iv can be determined as follows: D _iv = kEH (where k is a constant) (3) This division number is required to be a natural number, but it is preferable to set it to a multiple of 2 or a power of 2 in order to facilitate division. The strain amount H shown in the above equation (1) represents the parallelism between the vectors a and c and the parallelism between the vectors b and d, but since the area component is also included, only the pure strain component is included. If it is desired to obtain, normalization may be performed by dividing by, for example, an area component. As a factor for determining the number of divisions, in addition to the above-mentioned distortion and size, the "thinness" of a polygon (quadrangle) and the like can be considered.

After the number of polygons (quadrangles) to be divided is determined as described above, in step S35, the polygon is divided into some small polygons, for example, as shown in FIG. FIG. 5 shows an example of four divisions, and B of FIG.
When the four vertices of the polygon (quadrangle) shown in FIG. 3 are A, B, C, and D, a division point M that divides the side AB, a division point N of the side BC, a division point P of the side CD, and a division of the side DA. For the point Q, the average of the respective end points, that is, M = (A + B) / 2 N = (B + C) / 2 P = (D + C) / 2 Q = (A + D) / 2 Can be calculated easily by obtaining the average of four vertices, that is, O = (A + B + C + D) / 4.

In step S36, similar division is performed on the texture image side as shown in FIG.

After the fine division is completed in this way,
As shown in FIG. 5, triangulation is performed on each small polygon, and in step S37, a primary conversion formula is obtained for each small triangle. This linear conversion formula is for obtaining the coordinates of each point of the texture image corresponding to the position of the pixel inside the above-mentioned minute triangle based on the coordinates of the texture image corresponding to each vertex of the minute triangle on the screen image side. By using this linear conversion equation, in step S38, a point on the texture image corresponding to a pixel included in the small polygon is obtained, and the pixel data is written in the pixel position in the small polygon to perform drawing. .

At the next step S39, the above step S
It is determined whether or not the processes of 37 and S38 have been executed for all the small polygons. If NO, step S3.
Returning to step 7, a primary conversion formula is created for the small polygons that have not been subjected to the above processing, and the drawing processing is performed in step S38. If YES is determined in the step S39, this texture mapping process is ended.

According to such an embodiment, in the polygon before division, the bending of the texture which is conspicuous on the diagonal line becomes inconspicuous, and moreover, the number of divisions of the polygon is adaptive according to the "distortion", "size", etc. of the polygon. Since it is understood, the amount of calculation does not increase unnecessarily. Further, since the calculation increased by the division is the calculation after the coordinate conversion, the calculation amount can be significantly reduced as compared with the case where the polygon is divided from the beginning and the coordinate calculation is performed for all the vertices.

[0037]

As is apparent from the above description, according to the present invention, the screen coordinates obtained from the vertices of each polygonal area (so-called polygon) which is a unit forming an object to be displayed as an image are calculated. The number of divisions of the polygonal area is determined according to the information on the shape of the polygonal area (strain amount or size), and a plurality of divided polygons are interpolated from the screen coordinates of these vertices according to the number of divisions. The area is divided into areas (so-called small polygons), and the texture mapping of each divided polygonal area is performed using the screen coordinates of each vertex of each divided polygonal area. Therefore, it is possible to prevent the image quality deterioration such as the refraction of the texture on the diagonal line of the polygon and to adaptively change the division number according to the distortion amount and size of the polygon. When the size is small, the number of divisions is also small, and there is no unnecessary increase in the amount of calculation. Further, even if the number of divisions increases, the number of coordinate conversions does not increase, but only the number of interpolations increases, so the increase in the amount of calculation can be small.

[Brief description of drawings]

FIG. 1 is a block circuit diagram showing an example of an image creating apparatus to which an embodiment of a texture mapping apparatus according to the present invention is applied.

FIG. 2 is a flowchart for explaining the operation of the embodiment.

FIG. 3 is a diagram for explaining the distortion and size of a polygon used in the one embodiment.

FIG. 4 is a diagram for explaining an example of an evaluation formula for evaluating the distortion and size of a polygon used in the embodiment.

FIG. 5 is a diagram for explaining texture mapping of the embodiment.

FIG. 6 is a block circuit diagram showing an example of a conventional image creating apparatus to which texture mapping is applied.

FIG. 7 is a flowchart for explaining the flow of conventional texture mapping processing.

FIG. 8 is a diagram for explaining a conventional texture mapping process.

FIG. 9 is a diagram for explaining a conventional texture mapping process.

FIG. 10 is a flow chart for explaining a flow of processing involving polygon division of conventional texture mapping.

FIG. 11 is a diagram for explaining a conventional texture mapping process involving polygon division.

FIG. 12 is a diagram for explaining a conventional texture mapping process involving polygon division.

[Explanation of symbols]

 11-CPU 12-main memory 14-video memory 16-graphic processor 21-screen coordinate calculation function unit 22-polygon division Number determination function part 23 ... Polygon division function part 24 ... Texture mapping function part

Claims (4)

[Claims] 1. A texture mapping device for pasting a desired texture image onto a polygonal area, which is a unit constituting an object to be displayed as an image, wherein the multiplicity of pixels obtained from the screen coordinates of each vertex of the polygonal area. A means for determining the number of divisions of the polygonal area according to information on the shape of the polygonal area; and dividing into a plurality of divisional polygonal areas by interpolation from the screen coordinates of each vertex of the polygonal area according to the number of divisions. And a means for performing texture mapping of each divided polygonal area using the screen coordinates of each vertex of each divided polygonal area. 2. The texture mapping apparatus according to claim 1, wherein a strain amount of the polygonal area is used as the information on the shape. 3. The texture mapping device according to claim 1, wherein the area of the polygonal region is used as the information on the shape. 4. The texture mapping apparatus according to claim 1, wherein a strain amount and an area of the polygonal region are used as the information on the shape.