JP3327986B2 - Image creation device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[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 to a television receiver, a monitor receiver, a CRT display device, or the like and displayed. When generating or creating image data, so-called textures (fabrics, ground patterns)
In some cases, a texture mapping technique is used in which the image is pasted on a desired surface (polygonal area serving as a unit constituting an object to be displayed, a so-called polygon) such as a polyhedron to be displayed.

FIG. 6 is a block diagram showing an example of the configuration of a conventional image forming apparatus having a texture mapping function. In FIG. 6, a CPU 101 including a microprocessor or the like 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) serving as a source of the texture, and a display / output image generated or created. Video memory 104 where data is stored
Are at least connected. The CPU 101 reads the data of the texture source image from the video memory 103, modifies the data if necessary,
Write to. The data of the display output image written in the display area of the video memory 104 is stored in the D / A converter 10.
In step 5, it is converted into an analog signal and taken out as a video output.

When a texture mapping process is performed by using an image forming apparatus having a configuration as shown in FIG. 6, an arbitrary one so-called polygon (polygon area serving as a unit constituting an object to be displayed) is used. For example, the following method is used to paste a predetermined texture image into the image. This method will be described with reference to the flowchart in 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 transformation matrix (step S9).
1) and addition of the translation vector (step S92)
In the coordinate system fixed on the screen for display.
Find dimensional coordinates.

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

[0007] Since the correspondence between the texture image and the polygon on the screen at the three vertices of each triangle has been established, a primary conversion equation is created based on the correspondence (step S94).
be able to. A point on the texture image corresponding to a pixel included in the polygon is obtained by using this linear conversion formula, and the pixel value is written to a 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. Then, the above-described mapping operation is performed on each of the triangles 82 and 83. FIG. 8A shows a corresponding square 81t and two divided triangles 82t and 83t on the texture image side.

FIG. 9 shows a square 8 on the texture image side when a lattice pattern (grid ground) is used as a specific example of the texture.
1t and two divided triangles 82t and 83t, and a rectangle 81 on the display (screen) image side on which the divided triangles 82t and 83t are 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, the texture mapping by the above-described method, for example, as shown in FIG. At this point, refraction of the texture occurs, which impairs the quality of the displayed image.

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

That is, first, in step S71,
The polygon is divided into several (for example, four) small polygons 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).

From the next step S73, the processing from the above-mentioned steps S91 to S95 in FIG. 7 is performed for each divided small polygon. That is, steps S73, S74, S75, S76, and S77 in FIG.
Steps S91, S92, S93, S9 in FIG.
4 and S95, and a similar process is performed on the small polygon. In step S78, it is determined whether or not the processing in steps S91 to S95 has been performed for all the small polygons. If NO, the process returns to step S73. If YES, the process ends. Completed texture mapping.

By performing texture mapping processing for each of the small polygons obtained by dividing such polygons, image distortion occurs only in each of the small polygons, and overall image quality degradation is reduced. Become.

FIG. 12 shows a texture image side when a lattice pattern (grid grid) is used as a specific example of the texture, and FIG.
B indicates a quadrangular polygon on the display (screen) image side to which this is mapped. This FIG.
9B and B in FIG. 9 described above, the texture bend on the diagonal line of the polygon (quadrilateral) is shown in FIG.
B is less (less noticeable)
You can see that.

[0016]

The above-mentioned FIG.
According to the method described in (1), since the number of vertices of the polygon increases in proportion to the number of divisions, the total calculation amount also increases. That is, when a quadrilateral is assumed as a polygon, when texture mapping is performed on the quadrilateral polygon, (1) the image quality deteriorates diagonally unless the polygon is re-divided. (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, calculation becomes useless when the polygon before division is small. There is a problem.

The present invention has been made in view of such circumstances, and can effectively improve image quality deterioration such as bending of a texture on a diagonal line of a polygon without greatly increasing the amount of calculation. It is an object of the present invention to provide a simple image creating apparatus and an image creating method.

[0018]

An image forming apparatus according to the present invention is an image forming apparatus for forming an output image by pasting a desired texture image to a polygon which is a unit constituting a shape to be displayed. A screen coordinate calculation function unit that calculates screen coordinates of each vertex of the polygon; and a division number of the polygon according to information on the shape of the polygon obtained from the screen coordinates of each vertex of the polygon. A polygon division number determining function unit to be determined;
A polygon division function section that divides the polygon into a plurality of small polygons by interpolation according to the screen coordinates of each vertex of the polygon and the number of divisions, and screen coordinates of each vertex of the divided small polygon. And a texture mapping function unit for performing texture mapping for each small polygon. Here, the polygon division number determination function unit may determine the polygon division number using the distortion amount and / or area of the polygon in screen coordinates as information on the polygon shape. Further, the polygon division number determining function unit may determine the polygon division number using the distortion amount and area of the polygon in the screen coordinates as information on the polygon shape. Further, the polygon division number determining function unit may determine the polygon division number based on the parallelism of the opposite side of the polygon in screen coordinates when the polygon is a quadrangle. Further, when the polygon division number determination function unit described above, when the polygon in the screen coordinates is represented by a square ABCD, as the information on the shape of the polygon, the distortion amount H of the polygon defined by the following equation H, H = ( a ₀ -c ₀ ) ² + (a ₁ -c ₁ ) ² + (b ₀ -d ₀ ) ² + (b ₁ -d ₁ ) ² (where a ₀ and a ₁ are components of the vector a of the side AB , B ₀ and b ₁ are sides A
Components of vector b of D, c ₀ and c ₁ are components of vector c of side DC,
d ₀ and d ₁ may be determined on the basis of the vector BC of the side BC). Further, the polygon division number determining function unit may determine the polygon division number based on the fineness of the polygon in the screen coordinates when the polygon is a quadrangle. Further, the texture mapping function unit may divide the texture image according to the number of polygon divisions, and perform texture mapping for each small polygon using the divided texture image. .

The image forming method according to the present invention is an image forming method for forming an output image by pasting a desired texture image to a polygon, which is a unit constituting a shape to be displayed, wherein each vertex of the polygon is The process of calculating the screen coordinates of the polygon, the process of determining the number of divisions of the polygon in accordance with the information on the shape of the polygon obtained from the screen coordinates of each vertex of the polygon, and the process of determining the number of divisions of the polygon in accordance with the screen coordinates and the number of divisions And a process of dividing a polygon into a plurality of small polygons by interpolation, and a process of performing texture mapping for each small polygon using the screen coordinates of each vertex of the divided small polygon. Further, another image creation method according to the present invention includes a method of forming a shape to be displayed as an image by using polygons,
An output image is created by performing the following processes (a) to (d) for all polygons to which the texture image is to be pasted. (a) Processing for calculating the screen coordinates of each vertex of a polygon. (b) a process of determining the number of divisions of the polygon according to information on the shape of the polygon obtained from the screen coordinates of each vertex of the polygon. (c) a process of dividing the polygon into a plurality of small polygons by interpolation according to the screen coordinates of each vertex of the polygon and the number of divisions.
(d) A process of performing texture mapping for each small polygon using the screen coordinates of each vertex of the divided small polygon. Here, the process of determining the number of divisions of the polygon may include a process of determining the number of divisions of the polygon using the distortion amount or area of the polygon as information on the shape of the polygon. Further, the process of determining the number of divisions of the polygon may include a process of determining the number of divisions of the polygon using the distortion amount and area of the polygon in screen coordinates as information on the shape of the polygon. Further, the process of determining the number of divisions of the polygon may include a process of determining the number of divisions of the polygon based on the parallelism of the opposite side of the polygon in screen coordinates when the polygon is a quadrangle. .

[0020]

The image quality deterioration 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 determined by the distortion amount and area (size) of the polygon. ), The necessary minimum division is performed, and an unnecessary increase in the amount of calculation can be prevented. The vertex coordinates of each small polygon in the screen coordinate system (each divided polygon area) are obtained by interpolation from the vertex coordinates of the original polygon in the screen coordinate system. Need not be obtained by coordinate transformation, and the increase in the amount of calculation is small.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments according to the present invention will be described below with reference to the drawings. FIG. 1 is a functional block diagram showing a schematic configuration of a main part of an embodiment of an image forming apparatus according to the present invention.

In FIG. 1, a CPU 11 composed of a microprocessor or the like is connected to a bus line 19, which is connected to 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 graphics processor 1 for generating an image
6, and a video memory 15 for storing the generated image is connected to the graphic processor 16. Here, the main memory 12 stores not only programs but also three-dimensional vertex coordinates (local coordinates or object coordinates) of the object to be drawn, a coordinate conversion matrix, and units constituting each surface of the displayed object. Various information such as information indicating a storage location of a so-called texture image to be pasted on a polygonal area (a so-called polygon) is stored. The CPU 11 extracts necessary information from the main memory 12 according to the execution of the program stored in the main memory 12 and transfers the information to the graphic processor 16.

The graphic processor 16 performs processing such as creation and drawing of an image to be displayed. In particular, for main processing related to texture mapping,
This will be described using functional blocks. These functional blocks represent each function realized in software as hardware.

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

The polygon division number determining function unit 22 calculates the polygon division number in accordance with information on the shape of the polygon (unit polygon area) obtained from the screen coordinates of each vertex of the polygon.
The number of divisions of the polygon is determined. Specifically, when the polygon is a quadrangle, the number of polygon divisions is determined according to the “distortion” and “size (or area)” of the two-dimensional coordinates on the screen at the four vertices. For example, the “strain” increases as the shape shifts from the parallelogram. The “size” is a size (area) in the screen coordinate system, that is, an apparent size.

The polygon division function unit 23 divides the polygon into a plurality of divided areas (small polygons) by interpolation according to the number of divisions based on the screen coordinates of each vertex of the polygon. In this case, the half 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 texture mapping of each small polygon using the screen coordinates of each vertex of each divided area (small polygon). Specifically, if the polygon is a quadrangle, and the small polygon obtained by dividing the polygon is also a quadrangle,
Triangle division is performed for each small polygon, a primary conversion formula is determined for each triangle, and a point on the texture image corresponding to the pixel included in each small polygon is determined using the primary conversion formula. What is necessary is just to write in the pixel in a 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 the sake of simplicity, it is assumed that, for example, a quadrangle is used as the polygon, which is a polygonal area serving as a unit component of an object for image display.

The three-dimensional coordinates (local coordinate system) of the four vertices of the quadrangle as a specific example of the above-described polygon are multiplied by the coordinate transformation matrix in step S31, and the parallel movement vector is added in step S32. To obtain three-dimensional coordinates in a coordinate system fixed to the screen (screen coordinate system). In the next step S33, the three-dimensional coordinates in the screen coordinate system are perspective-transformed to obtain 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-described process, and at least these "strain" and "size" are obtained. According to one of them, the number of divisions of the quadrangle which is the polygon is determined. here,
FIG. 3 is a diagram for explaining the definitions of the “strain” and “magnitude”. As shown in FIGS. 3A and 3B, as the shape is shifted from the parallelogram, the “strain” increases. As shown in 3C and 3D, the magnitude of “size” is determined by the apparent size (area) in the screen coordinate system. The number of divisions of the square is determined according to the magnitude of the “strain” and “size”.

An example of an evaluation formula for determining the number of divisions according to the "strain" and "magnitude" will be described with reference to FIG. The four vertices of the polygon (square) shown in FIG. 4 are A, B, C, and D, the vector of the side AB is a, and the side A is
The vector b of D, the vector of side DC is c, the vector d of side BC is x, and the x and y components of vector a orthogonal to each other are (a ₀ , a ₁ ), and each component of vector b is (b ₀ , b ₁ ), and each component of the vector c by (c ₀ , c
₁ ) and when each component of the vector d is (d ₀ , d ₁ ), the amount (strain amount) H of the “strain” is represented by H = (a ₀ −c ₀ ) ² + (a ₁ −c ₁₎ ) ² + (b ₀ −d ₀ ) ² + (b ₁ −d ₁ ) ² (1) Further, the quantity E representing the “size” is represented by E = | a ₀ b ₁ −a ₁ b ₀ | + | c ₀ d ₁ −c ₁ d ₀ | (2) Then, using these values H and E, the number of divisions D _iv, D _iv = kEH (where k is a constant) can be determined as (3). The number of divisions is required to be a natural number, but is preferably 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 includes an area component. When it is desired to calculate the normalization by, for example, dividing by the area component. As an element for determining the number of divisions, “thinness” of a polygon (quadrangle) and the like can be considered in addition to the distortion and the size.

When the number of polygons (squares) to be divided is determined as described above, in step S35, the polygon is divided into several small polygons as shown in FIG. 5, for example. FIG. 5 shows an example of four divisions, and FIG.
When the four vertices of the polygon (square) shown in (1) are A, B, C, and D, the division point M that divides the side AB into two, the division point N of the side BC, the division point P of the side CD, and the division of the side DA For the point Q, the average of both end points, that is, M = (A + B) / 2 N = (B + C) / 2 P = (D + C) / 2 Q = (A + D) / 2 Can be easily calculated by calculating 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 division has been made sufficiently fine,
As shown in FIG. 5, triangulation is performed on each small polygon, and a primary conversion formula is obtained for each minute triangle in step S37. This primary conversion formula is for obtaining the coordinates of each point of the texture image corresponding to the position of the pixel inside the small triangle based on the coordinates of the texture image corresponding to each vertex of the small triangle on the screen image side. In step S38, a point on the texture image corresponding to the pixel included in the small polygon is obtained by using the linear conversion formula, and the pixel data is written to a pixel position in the small polygon to perform drawing. .

In the next step S39, the above step S
It is determined whether or not the processing of steps S37 and S38 has been performed for all the small polygons.
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. When YES is determined in the step S39, the texture mapping process ends.

According to such an embodiment, in the polygon before division, the bending of the texture conspicuous on the diagonal line becomes inconspicuous, and the number of divisions of the polygon is adaptively determined according to the "distortion", "size", etc. of the polygon. Therefore, the amount of calculation does not needlessly increase. Furthermore, since the calculation that is increased by the division is a calculation after the coordinate conversion, the amount of calculation can be significantly reduced as compared with the case where the polygon is divided from the beginning and the coordinates are calculated for all vertices.

[0037]

As is clear from the above description, according to the present invention, according to the present invention, a polygonal area (a so-called polygon) which is a unit constituting an object to be displayed as an image is obtained from the screen coordinates of each vertex of the polygon. The number of divisions of the polygonal area is determined according to information (distortion amount and size) on the shape of the polygonal area, and a plurality of divided polygons are interpolated from the screen coordinates of these vertices according to the number of divisions. The divided polygon regions are divided into regions (so-called small polygons), and texture mapping of each divided polygon region is performed using the screen coordinates of each vertex of each divided polygon region. Therefore, image quality deterioration such as refraction of texture on the diagonal line of the polygon can be prevented, and the number of divisions is adaptively changed according to the distortion amount and size of the polygon. If the size is small, the number of divisions is also small, and there is no unnecessary increase in the calculation amount. Further, even if the number of divisions increases, the number of coordinate transformations does not increase, and only the number of interpolations increases, so that the amount of calculation can be reduced.

[Brief description of the drawings]

FIG. 1 is a block circuit diagram showing an embodiment of an image forming apparatus according to the present invention.

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

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

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

FIG. 5 is a diagram for explaining texture mapping according to the embodiment;

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

FIG. 7 is a flowchart illustrating a flow of a conventional texture mapping process.

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 flowchart for explaining a flow of processing involving polygon division in 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 CPU 12 Main memory 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

Continuation of front page (56) References JP-A-63-83871 (JP, A) JP-A-58-219664 (JP, A) JP-A-4-116690 (JP, A) JP-A-4-152390 (JP) JP-A-2-105979 (JP, A) JP-A-2-71384 (JP, A) JP-A-4-15772 (JP, A) JP-A-5-46775 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G06T 15/00

Claims (2)

(57) [Claims] 1. An image creating apparatus for creating an output image by pasting a desired texture image to a polygon which is a unit constituting a shape to be image-displayed, and calculating a screen coordinate of each vertex of the polygon. A screen coordinate calculation function unit that determines the number of divisions of the polygon according to information about the shape of the polygon obtained from the screen coordinates of each vertex of the polygon; and a polygon division number determination function unit that determines the number of divisions of the polygon. A polygon division function unit that divides the polygon into a plurality of small polygons by interpolation according to the screen coordinates and the number of divisions, and uses the screen coordinates of each vertex of the divided small polygons for each small polygon. and a texture mapping function unit for performing texture mapping, before
The polygon division number determination function unit determines that the polygon is a quadrangle.
, The polygon in screen coordinates
The division number of the polygon is determined based on the parallelism of the opposite side.
Image creation device to decide . 2. An image creating apparatus for creating an output image by pasting a desired texture image to a polygon which is a unit constituting a shape to be displayed, and calculating screen coordinates of each vertex of the polygon. A screen coordinate calculation function unit that determines the number of divisions of the polygon according to information about the shape of the polygon obtained from the screen coordinates of each vertex of the polygon; and a polygon division number determination function unit that determines the number of divisions of the polygon. A polygon division function unit that divides the polygon into a plurality of small polygons by interpolation according to the screen coordinates and the number of divisions, and uses the screen coordinates of each vertex of the divided small polygons for each small polygon. and a texture mapping function unit for performing texture mapping, before
The polygon division number determination function unit
When the polygon is represented by a square ABCD,
As information on the shape of rigon, it is defined by the following equation.
The distortion amount H of the polygon, H = (a ₀ -c ₀ ) ² + (a ₁ -c ₁ ) ² + (b ₀ -d ₀ ) ² + (b ₁ -d ₁ ) ² (where a ₀ , a ₁ are the components of the vector a of the side AB, and b ₀ , b ₁ are the sides A
Components of vector b of D, c ₀ and c ₁ are components of vector c of side DC,
d ₀ and d ₁ are components of the vector d of the side BC)
An image creation device that determines the number of divisions of the image.