JP3652586B2 - Image drawing system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to three-dimensional computer graphics (CG), and more particularly to an image drawing method for displaying a three-dimensional (3D) model in a cell animation style.
[0002]
[Prior art]
With recent improvements in hardware performance, it has become possible for home video game machines to realize 3D CG animation by drawing 3D CG in real time.
[0003]
When drawing such a three-dimensional CG, a method called Gouraud shading is generally used as a method for obtaining the luminance value of the surface of the 3D model.
[0004]
In Gouraud shading, first calculate the luminance value (gradation) of each vertex of the polygon that makes up the 3D model, and then smoothly complement the luminance value of the vertex with the luminance value of the other pixels that make up the polygon. To calculate. Gouraud shading can be executed very fast because it is implemented in hardware on modern drawing chips.
[0005]
FIG. 11 is a diagram illustrating an example of a drawing result by Gouraud shading. As shown in the figure, the luminance values of the pixels constituting the quadrangle are smooth complements of the luminance values of the four vertices, and a shaded image is obtained.
[0006]
[Problems to be solved by the invention]
On the other hand, depending on the contents of the game, etc., there is a case where it is desired to display the 3D CG like a conventional cell animation. In cel animation, since a person draws a line drawing and creates an image by coloring it, it is difficult to realize a smooth gradation, and there are few gradation expressions. Therefore, in order to display a cell animation tone, it is necessary to display a gradation of about 4 gradations instead of a smooth gradation.
[0007]
However, as described above, when Gouraud shading is used, smooth gradations are obtained. Therefore, in order to display gradations like cel animation, smooth gradations are converted into four gradations by some method. It must be dropped to the extent.
[0008]
For this purpose, for example, there is a method of dividing a polygon by calculating the position of a boundary of a desired gradation. However, in this method, the number of polygons increases, so the amount of calculation increases accordingly, and the number of polygons If it becomes the order of thousands or tens of thousands, the processing speed will be in time.
[0009]
An object of the present invention is to provide an image drawing method that enables display such as cell animation without increasing the number of polygons.
[0010]
[Means for Solving the Problems]
The image drawing system according to the present invention includes a luminance value calculating unit that calculates a luminance value of each vertex of a polygon constituting a three-dimensional model, a texture storing unit that stores a texture for gradation expression, and the luminance value calculating unit. Texture position calculating means for calculating the position of the texture for gradation expression corresponding to the calculated luminance value of each vertex, and the texture for gradation expression specified by the calculated position are translucent on the surface of the polygon. And mapping means for pasting.
[0011]
Further, the image drawing method according to the present invention calculates the luminance value of each vertex of the polygon constituting the three-dimensional model, calculates the position of the gradation expression texture corresponding to the calculated luminance value of each vertex, The gradation expression texture defined by the calculated position is pasted on the surface of the polygon in a translucent manner.
[0012]
The recording medium according to the present invention is a recording medium on which an image drawing program is recorded. Then, the image drawing program calculates a luminance value calculation step for calculating the luminance value of each vertex of the polygon constituting the three-dimensional model, and calculates the coordinate value of the gradation expression texture corresponding to the calculated luminance value of each vertex. A texture coordinate value calculating step, and a mapping step for instructing that the texture for gradation expression defined by the calculated coordinate value is pasted on the surface of the polygon in a translucent manner.
[0013]
In this case, the mapping step mixes the first drawing step for instructing normal drawing of the polygon, the texture for gradation expression, and the drawing result drawn in the first drawing step. You may make it provide the 2nd drawing step which instruct | indicates drawing.
[0014]
In the above case, the tone expression texture may have, for example, a predetermined number of tones, or the tone changes discontinuously according to the first parameter. The position where the shading changes discontinuously may change according to the second parameter.
[0015]
In addition, the said program can be distributed via portable recording media, such as CD-ROM, DVD-ROM, and a memory card, and a network, for example.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0017]
First, an entertainment apparatus to which the present invention is applied will be described. This entertainment apparatus executes an application such as a game provided by a recording medium such as a CD / DVD or a network, for example.
[0018]
FIG. 1 is a block diagram showing a configuration of an entertainment apparatus to which the present invention is applied.
[0019]
As shown in the figure, the entertainment apparatus includes an MPU 100, a graphics processor (GP) 110, an I / O processor (IOP) 120, a CD / DVD decoder 130, an SPU 140, an OSROM 150, and a main memory 160. And an IOP memory 170.
[0020]
The MPU 100 and the graphics processor 110 are connected by a bus 101, and the MPU 100 and the IOP 120 are connected by a bus 102. The IOP 120, the CD / DVD decoder 130, the SPU 140, and the OSROM 150 are connected to the bus 103.
[0021]
In addition, a main memory 160 is connected to the MPU 100, and an IOP memory 170 is connected to the IOP 120. Further, a controller (PAD) 180 is connected to the IOP 120.
[0022]
The MPU 100 is the main CPU of the entertainment apparatus. The MPU 100 performs a predetermined process by executing a program stored in the OSROM 150 or a program loaded from the CD or DVD into the main memory 160.
[0023]
The graphics processor 110 is a drawing processor that is responsible for the rendering function of the entertainment apparatus. The graphics processor 110 performs a drawing process in accordance with an instruction from the MPU 100. Details of the graphics processor 110 will be described later.
[0024]
The IOP 120 is an input / output sub-processor that controls data exchange between the MPU 100 and peripheral devices (such as the CD / DVD decoder 130 and the SPU 140).
[0025]
The CD / DVD decoder 130 reads data from a CD or DVD loaded in the drive and transfers it to the main memory 160.
[0026]
The SPU 140 is a sound reproduction processing processor, and reproduces sound data (PCM data or the like) stored in a sound buffer (not shown) at a predetermined sampling frequency based on a sound generation command from the MPU 100.
[0027]
The OSROM 150 is a ROM that stores programs executed by the MPU 100 and the IOP 120 at the time of startup or the like.
[0028]
The main memory 160 is a main memory of the MPU 100, and stores commands executed by the MPU 100, data used by the MPU 100, and the like.
[0029]
The IOP memory 170 is a main memory of the IOP 120 and stores instructions executed by the IOP 120, data used by the IOP 120, and the like.
[0030]
The controller (PAD) 180 is an interface for transmitting a player's intention to an application or the like during execution of a game or the like.
[0031]
Next, the internal configuration of the graphics processor 110 will be described.
[0032]
FIG. 2 is a diagram illustrating an internal configuration of the graphics processor 110. As shown in the figure, the graphics processor 110 includes a host interface unit 200, a drawing function block 210, a local memory 220, and a CRTC unit 230.
[0033]
The host interface unit 200 is an interface unit for exchanging data with the MPU 100.
[0034]
The drawing function block 210 is a logic circuit unit that performs rendering processing based on an instruction from the MPU 100. The drawing function block 210 includes 16 digital differential analyzers (DDA) and 16 pixel engines, respectively, and processes up to 16 pieces of pixel data of 64 bits (color information 32 bits, Z value 32 bits) in parallel. The DDA calculates RGB values, Z values, texture values, etc. based on the vertex information received from the MPU 100. Based on these data, the pixel engine performs processes such as texture mapping and α blending to generate final pixel data.
[0035]
The local memory 220 stores pixel data generated by the drawing function block 210, texture data transferred from the MPU 100, and the like.
[0036]
The CRTC unit 230 outputs the contents of the frame buffer area of the local memory 220 as a video signal in accordance with a designated output format (NTSC, PAL, VESA format, etc.).
[0037]
FIG. 3 is a diagram illustrating a configuration of the local memory 220. As shown in the figure, the local memory 220 has a frame buffer area 250, a Z buffer area 260, a texture buffer area 270, and a texture CLUT area 280.
[0038]
The frame buffer area 250 and the Z buffer area 260 are drawing target areas. The frame buffer area 250 stores pixels of the drawing result, and the Z buffer area 260 stores the Z value of the drawing result.
[0039]
The texture buffer area 270 stores texture image data, and the texture CLUT area 280 stores a color look-up table (CLUT) used when the texture is an index color.
[0040]
The regions 250 to 280 can be freely arranged in any order in any address on the local memory 220 by setting an appropriate value in a predetermined control register.
[0041]
Next, 3D model drawing processing executed by the entertainment apparatus having the above-described configuration will be described. The application draws an image based on the 3D model stored in the CD / DVD as necessary. In the following, a case where the drawing method according to the present invention is applied to a polygon model will be described, but the present invention can be applied to a spline model in exactly the same manner.
[0042]
First, the function of the graphic processor 110 used for realizing the drawing method will be described. In this drawing method, the texture mapping function and the α blending function of the graphic processor 110 are used.
[0043]
The texture mapping function refers to a function of drawing an image by pasting the texture (image data) stored in the texture buffer area 270 of the local memory 220 on the surface of the polygon.
[0044]
FIG. 4 is a diagram for explaining the texture mapping function of the graphics processor 110. As shown in the figure, when the texture mapping function is used, all or a part of the texture prepared in the texture buffer area 270 can be appropriately enlarged, reduced or deformed and pasted on the surface of the polygon. When instructing the graphics processor 110 to draw a polygon with a texture, the MPU 100 instructs the drawing by specifying the coordinate value of the texture corresponding to each vertex in addition to the coordinate value of each vertex of the polygon. .
[0045]
When the graphics processor 110 turns on the texture mapping function and is instructed to draw a polygon, the image is placed in the texture buffer area 270 based on the coordinate value of the texture specified for each vertex of the polygon. The data is referred to as a texture, and the texture mapping is performed by appropriately complementing the data.
[0046]
On the other hand, the α blending function of the graphics processor 110 refers to the RGB value and frame of the pixel generated according to the alpha value of the pixel generated according to the instruction from the MPU 100 or the alpha value stored in the frame buffer area 250. A function for rendering an image by blending (mixing) RGB values stored in the buffer area 250.
[0047]
The texture mapping function and the α blending function can be controlled on / off by setting appropriate values in predetermined control registers.
[0048]
In this rendering method, using these functions, a texture with gradations of several gradations is prepared in advance for gradation expression, and this texture is translucent and pasted on the surface of the 3D model. Realize tonal gradation expression.
[0049]
FIG. 5 is a diagram for explaining gradation expression by this drawing method. As shown in the figure, the position of the gradation expression texture 51 corresponding to the luminance value at each vertex of the polygon 50 is calculated, and the gradation expression texture 52 (one-dimensional texture) defined by the calculated position is calculated. Is complemented appropriately, and a gradation display is realized by pasting it semi-transparently.
[0050]
Next, the flow of the drawing process will be described. FIG. 6 is a flowchart showing the flow of the drawing process. This process is executed by the MPU 100.
[0051]
First, the texture for gradation expression is transferred to the texture buffer area 270 of the local memory 220 (S600).
[0052]
Next, the brightness (luminance value) at each vertex is calculated from the positional relationship between each vertex of the polygon constituting the 3D model and the light source (S602).
[0053]
Next, based on the brightness of each vertex, the position (coordinate value) of the gradation expression texture corresponding to the brightness is calculated (S604).
[0054]
FIG. 7 is a diagram for explaining the relationship between the brightness and the position of the texture for gradation expression. As shown in the figure, the tone expression texture 70 has four levels of shading (darkness), and the tone becomes discontinuously darker from left to right. For such a tone expression texture 70, for example, a position P1 is calculated as a position corresponding to 90% brightness in proportion to brightness, and a position P2 is set as a position corresponding to 30% brightness. Is calculated.
[0055]
FIG. 8 is a diagram illustrating another example of the texture for gradation expression. As shown in the drawing, the gradation expressing texture 80 is discontinuously dark as it goes from left to right as in the gradation expressing texture 70 shown in FIG. Furthermore, the gradation expressing texture 80 differs in the position where the gradation changes depending on the position in the vertical direction.
[0056]
When the texture as shown in FIG. 8 is used, the gradation of the surface of each 3D model can be changed without changing the brightness calculation value depending on how the position in the vertical direction is selected. For example, it is possible to control the atmosphere like the skin of a person with a large number of gradations and the metallic expression of the gradations, such as a robot, simply by selecting the texture in the vertical direction.
[0057]
Next, the graphics processor 110 is instructed to normally draw the polygons constituting the 3D model (S606). As a result, the graphics processor 110 renders the 3D model in the frame buffer area 250 without shading.
[0058]
Next, the texture mapping function and the α blending function are turned on, the texture coordinate value corresponding to each vertex of the polygon is designated, and the graphics processor 110 is instructed to draw the polygon constituting the 3D model (S608). As a result, the graphics processor 110 renders an image in which the designated gradation expression texture is translucently pasted on the polygon surface rendered in the frame buffer area 250 in step S606.
[0059]
Through the processing as described above, it is possible to display a cell animation tone.
[0060]
FIG. 9 is a diagram for conceptually explaining a drawing result by the conventional drawing method and a drawing state by the drawing method.
[0061]
FIG. 5A shows a drawing result drawn by performing conventional Gouraud shading. As shown in the figure, the gradation expression is smooth.
[0062]
On the other hand, in this drawing method, first, as shown in FIG. 4B, drawing is performed without shading, and then a texture as shown in FIG. Cut out from the texture buffer area 270 and paste the cut out texture into a drawing result drawn without shading in a translucent manner. By such processing, a cell animation-like drawing result as shown in FIG.
[0063]
FIG. 10 is a diagram showing an example of an image drawn by the drawing method according to the present invention. As shown in the figure, the character is displayed with few gradations and has a display screen like a cell animation.
[0064]
【The invention's effect】
As described above in detail, according to the present invention, display like a cell animation is possible without increasing the number of polygons.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of an entertainment apparatus to which the present invention is applied.
FIG. 2 is a diagram showing an internal configuration of the graphics processor 110. FIG.
3 is a diagram showing a configuration of a local memory 220. FIG.
FIG. 4 is a diagram for explaining a texture mapping function of the graphics processor 110;
FIG. 5 is a diagram for explaining gradation expression according to the present invention.
FIG. 6 is a flowchart showing a flow of a drawing process according to the present invention.
FIG. 7 is a diagram for explaining the relationship between brightness and the position of a texture for gradation expression.
FIG. 8 is a diagram illustrating an example of a texture for gradation expression.
FIG. 9 is a diagram for conceptually explaining a drawing result by a conventional drawing method and a drawing state by the drawing method according to the present invention.
FIG. 10 is a diagram showing an example of an image drawn by the drawing method according to the present invention.
FIG. 11 is a diagram illustrating an example of a drawing result by Gouraud shading.
[Explanation of symbols]
100 MPU
110 Graphics processor (GP)
120 I / O processor (IOP)
130 CD / DVD decoder 140 SPU
150 OSROM
160 Main memory 170 IOP memory 180 Controller (PAD)

Claims (5)

Luminance value calculating means for calculating the luminance value of each vertex of the polygon constituting the three-dimensional model;
Texture storing means for storing a texture for gradation expression in which the gradation changes discontinuously according to the first parameter and the gradation number of the gradation changes discontinuously according to the second parameter ;
Texture position calculating means for calculating the position of the texture for gradation expression corresponding to the luminance value of each vertex calculated by the luminance value calculating means;
Mapping means for pasting the texture for gradation expression specified by the calculated position to the surface of the polygon in a translucent manner;
An image drawing system comprising: Calculate the luminance value of each vertex of the polygon that makes up the 3D model,
Corresponds to the calculated luminance value in the texture for gradation expression in which the gradation changes discontinuously according to the first parameter, and the number of gradation gradations changes discontinuously according to the second parameter. Calculate the position to
An image drawing method, wherein a texture for gradation expression specified by a calculated position is semi-transparently pasted on a surface of a polygon. A recording medium on which an image drawing program is recorded,
The image drawing program includes:
A luminance value calculating step for calculating a luminance value of each vertex of the polygon constituting the three-dimensional model;
The brightness of each vertex calculated in the gradation expression texture in which the shade changes discontinuously according to the first parameter and the number of shades of the shade that change discontinuously changes according to the second parameter. A texture coordinate calculation step for calculating a position corresponding to the value;
A mapping step for instructing to paste the texture for gradation expression defined by the calculated coordinate values on the surface of the polygon in a translucent manner;
A recording medium comprising: The mapping step includes
A first drawing step for instructing normal drawing of the polygon;
A second drawing step instructing to mix and draw the texture for gradation expression and the drawing result drawn in the first drawing step;
The recording medium according to claim 3, further comprising: A luminance value calculating step for calculating a luminance value of each vertex of the polygon constituting the three-dimensional model;
The brightness of each vertex calculated in the gradation expression texture in which the shade changes discontinuously according to the first parameter and the number of shades of the shade that change discontinuously changes according to the second parameter. A texture coordinate calculation step for calculating a coordinate value corresponding to the value;
A mapping step for instructing to render the texture for gradation expression specified by the calculated coordinate value by pasting it on the surface of the polygon in a translucent manner;
An image drawing program comprising:

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