JP4617501B2 - Texture mapping method, program and apparatus - Google Patents

Description

  The present invention relates to a data structure of texture data, and more particularly to a data structure suitable for cell shading.

Conventionally, a technique called cell shading is known as a texture mapping technique using multiple textures in the field of computer graphics. Cell shading is also called toon shading, and the texture data UV coordinates (reading address) are determined from the distance between the object (model) to be texture mapped and the light source, the angle between the normal vector of the object surface and the light vector, etc. This is a technique for performing shading by mapping the texture on the object surface by appropriately filtering luminance, color, and the like. FIG. 8 is an explanatory diagram of texture data used for conventional cell shading. The texture data 70 shown in the figure is for shading processing from white to black when the brightness of the object surface exceeds a certain threshold, and is normalized UV coordinate system (0.0 ≦ U ≦ 1.0 and 0.0 ≦ V ≦ 1.0), a data area 71 (0.0 ≦ U ≦ 0.5 and 0.0 ≦ V ≦ 1.0) in which white data is arranged, and black And a data area 72 (0.5 ≦ U ≦ 1.0 and 0.0 ≦ V ≦ 1.0) in which data is arranged. The UV coordinates referred to in the texture mapping can be obtained by the following two formulas.
U = a * I + b (1)
V = c * I + d (2)
Here, I is a luminance value obtained from the inner product of the normalized normal vector of the object surface and the normalized ray vector, and a, b, c, and d are constants. Since the cell shading technique is known, the details of a, b, c, and d are omitted. If the luminance I can be obtained, the UV coordinates on the texture data can be obtained from the equations (1) and (2). The movement locus of the UV coordinates when the value of the luminance I is changed becomes a straight line 73. As is clear from the figure, as a result of light source calculation, when setting the UV value of each vertex of the object, the angle formed by the normal vector and the ray vector on the object surface is small and small in the portion where the light hits well. A U value is specified and texture mapping is performed in white. On the other hand, a large U value is specified and texture mapping is performed in black at a portion where the angle between the normal vector and the light vector on the object surface is large and light does not hit much. The That is, when the U value exceeds 0.5, the pixels on the object surface are shaded from white to black. In this way, by performing the binary processing of white and black on the shading process, the difference between the exposed surface and the non-exposed surface on the object surface can be clarified, and so-called animated shading can be performed.

  However, in the conventional cell shading method, it is necessary to prepare texture data for shading according to various exposure conditions such as the color of the light source, the distance between the light source and the object, the light intensity of the light source, etc. In addition, there is a problem of wasting hardware resources. Originally, texture mapping expresses the details of an object by pasting a two-dimensional pattern or pattern on a two-dimensional plane. However, when texture mapping is used for shading as described above, shadow mapping is used. Since the texture data for use is only required in the one-dimensional direction, use of the two-dimensional texture data as the texture data for shading wastes memory. Such a problem will be described with reference to FIGS.

  FIG. 9 is an explanatory diagram for switching texture data to be used corresponding to the color of the light source. A red light source 41, a green light source 42, and a blue light source 43 are arranged in a virtual space as light sources for illuminating the object 50. Yes. Three types of texture data for binarized shading processing are prepared for each color light source. In the state shown in the figure, since the object 50 is at the position of the green light source 42, texture mapping may be performed using texture data for performing green shading processing. However, when the object 50 moves to the red light source 41 side beyond the boundary 61 between the red light source 41 and the green light source 42, it can no longer be shaded using the texture data for the green light source 42. Shading must be performed using the texture data for the red light source 41. When the texture data used at the boundary line 61 is suddenly switched, the shadow displayed on the surface of the object 50 is suddenly switched, which is extremely unnatural in graphics display. The same applies when the object 50 moves to the blue light source 43 side beyond the boundary 62 between the green light source 42 and the blue light source 43.

  FIG. 10 is an explanatory diagram of switching texture data to be used according to the positional relationship between the camera (virtual viewpoint) and the object. The light source 40, the object 50, and the camera 60 are arranged at predetermined positions. In 3D computer graphics, each polygon constituting the object 50 is modeled and converted to the world coordinate system, the field of view from the camera 60 to the camera viewpoint, 3D clipping processing, hidden surface processing, texture mapping processing, shading processing , Display priority processing, etc., and display on the video display. Since the shading applied to the object 50 differs in appearance depending on the distance between the camera 60 and the object 50, texture data for a plurality of types of shading processing is prepared in advance, and the distance between the object 50 and the camera 60 is constant. The texture used for shading is switched when the distance is exceeded. In the example shown in the figure, the texture to be used is switched when the object 50 moves farther than the camera 60 beyond the boundary 63. However, when the texture used at the boundary 63 is suddenly switched, the shadow displayed on the surface of the object 50 is suddenly switched, which is extremely unnatural in graphics display.

  Moreover, among the texture data 70 shown in FIG. 8, only the data on the straight line 73 is actually used, and other data areas are not used. ing.

  Therefore, the present invention solves the above-described problems, enables smooth shading, and also provides a data structure of texture data suitable for saving memory resources, a program for causing a computer system to execute texture mapping, and a texture mapping method And a texture mapping device.

  In order to solve the above-described problem, in the present invention, texture mapping is performed in order to access texture data including a computer-readable data area in which color data in which a gray scale is formed in two orthogonal directions is arranged. Based on a predetermined calculation formula from the luminance information of the object surface, the coordinates for accessing the data area in any one of the two directions are calculated, and the other one of the two directions The coordinates for accessing the data area are calculated based on an arbitrary value assigned to the dynamic variable, and the data area is read out by accessing the data area based on the calculated coordinates. Texture mapping to

  In the present invention, a program for causing a computer system to execute the above method can be recorded on a computer-readable recording medium. Examples of such recording media include optical recording media (CD-RAM, CD-ROM, DVD-RAM, DVD-ROM, DVD-R, PD disk, MD disk, MO disk, etc.) Recording medium), a magnetic recording medium (a recording medium capable of magnetically reading data such as a flexible disk, a magnetic card, and a magnetic tape), or a memory having a memory element such as a DRAM, SRAM, MRAM, or FRAM There are portable recording media such as cartridges.

  In addition, the above program is a client device (personal computer, game device, mobile phone equipped with a Web browser, PDA, palm-type personal computer, etc.) connected to an open network such as the Internet network or a packet communication network. In response to a request from a network server such as a Web server, it can be distributed on demand.

  According to the present invention, since texture mapping is performed using texture data including a computer-readable data area in which color data having gradations formed in two directions orthogonal to each other are arranged, predetermined information is obtained from luminance information on the object surface. Coordinates for accessing texture data can be obtained from the value obtained from the above formula and the value calculated from any value assigned to the dynamic variable, depending on the value assigned to the dynamic variable. Thus, the color tone, shading, etc. of the texture data to be read can be changed as appropriate. For this reason, shading with different shade colors can be seen to change naturally. Also, a plurality of texture data can be aggregated into a single texture data, and texture memory can be saved.

  Hereinafter, the present embodiment will be described with reference to the drawings.

  FIG. 7 is a functional block diagram for performing texture mapping on an object using texture data for shading and outputting a video signal to a video display. In the figure, 11 is a texture memory for storing texture data, 12 is a filter, 13 is a frame memory for writing image data for one screen, and 14 is a video signal generator for outputting a video signal to a video display. As a result of light source calculation corresponding to each pixel on the object surface or the vertex of the polygon constituting the object, luminance data, color data, etc. corresponding to each pixel or the vertex of the polygon are read from the texture memory 11, and then in the filter 12. The filter operation is performed with reference to the luminance data and color data of the surrounding pixels, and the processing result is written in the frame memory 13. The video signal generator 14 generates a video signal based on the image data written in the frame memory 13 and outputs it to a video display (not shown).

  FIG. 1 is an explanatory diagram of texture data according to the present embodiment. The texture data 20 shown in the figure shows a state in which the texture is expanded on the two-dimensional plane for convenience of explanation, but is not necessarily expanded on the two-dimensional plane in a state stored in the texture memory 11. The texture data has the same data structure as long as the relationship between the color data at arbitrary coordinates of the texture data satisfies the relationship shown in FIG. In other words, the “data structure” in this specification does not mean the relationship between individual bit data in a state in which the texture data is recorded on a recording medium such as a memory, but the read address of the texture data. This is the relationship between the color data of the defined individual coordinates. The color data includes information on luminance, hue, and saturation in the case of a chromatic color, and information on luminance (brightness) in the case of an achromatic color. Furthermore, in the case of a transparent color, information on transparency is included as color data, and in the case of semi-transparent with color, information on luminance, hue, and saturation is also included in addition to transparency.

As shown in FIG. 3, the texture data 20 is prepared for shading processing on the object surface when the object 50 moves in the horizontal direction in the figure under the red, green, and blue light sources 41, 42, and 43. It has been done. In the texture data 20, white texture data is arranged in the data region C10 where 0.0 ≦ U ≦ 0.5 and 0.0 ≦ V ≦ 1.0, and 0.5 ≦ U ≦ 1.0 and 0 In the data regions C1 to C9 where .0 ≦ V ≦ 1.0, the texture data for shading processing for the light sources 41, 42, and 43 are arranged at substantially equal intervals. More specifically, C1 is dark red, C2 is light red, C3 is light red and light green, C4 is light green, C5 is dark green, C6 is light green, C7 is light green and light blue, C8 is light blue and C9 is dark blue texture data. That is, corresponding to the positions of the light sources 41, 42, and 43, a plurality of shading texture data having different tones are arranged in the V coordinate direction. In the example shown in the figure, for convenience of explanation, nine levels of light and shade gradients are provided, but actually, a finer light and shade gradient of about several tens may be provided. Needless to say, setting the U and V coordinates of the texture in reverse does not change the essence of the invention. By providing an appropriate light / dark gradient according to the application, various shading processes can be realized, from an animation-style shading process for binarizing the shadow to a dramatic-style shading process for converting the shadow into multiple values. In the present embodiment, when shading processing is performed using the texture data 20, the equation (1) is used to obtain the U value by light source calculation, and the following ( 3) Formula is used.
V = d (3)
According to equation (3), regardless of the luminance I, the V value can be set by the value of the variable d. This variable d is a dynamic variable that can be arbitrarily changed on the program. For example, it can be changed in real time according to the distance between the light source and the object, and further, regardless of the positional relationship with the light source, It is also possible to change appropriately according to the game situation (for example, whether the player is in an advantageous situation, whether the score is increased, etc.) developed in the virtual space. How to set the value of d should be set appropriately by the programmer according to the use of various applications such as whether the present invention is used for computer graphics, art, or for games. Is possible.

  For example, in the example of FIG. 1, when the value of d is set to 0.15, a weak contrast can be expressed by the light red shading process, while when the value of d is set to 0.9, a dark blue color A strong contrast can be expressed by the shading process. If the value of d is defined in association with the distance to the light source, the value of d can be changed in real time in conjunction with the positional relationship between the object and the light source. For example, in the example of FIG. 3, coordinate axes are set in the horizontal direction in the drawing, the position of the light source 41 is d = 0.0, the position of the light source 42 is d = 0.5, and the position of the light source 43 is d = 1.0. Then, the d value approaches 0.0 as the object 50 approaches the light source 41, the d value approaches 0.5 as the object 50 approaches the light source 42, and the d value approaches 1.0 as the object 50 approaches the light source 43. In the example shown in the figure, since the object 50 is slightly leftward with respect to the position of the light source 42, if the d value on the coordinate axis is obtained and d = 0.35 is obtained, it is shaded on the surface of the object 50. The shade color is pale green.

  Thus, by using the U value for shading processing and the V value for shading color control, it is possible to realize smooth shading processing with three color light sources. Further, unlike the prior art, the shade color does not change drastically at the boundary set in advance with the positional relationship with the light source, so that smooth shading without a sense of incongruity can be realized. In addition, conventionally, it is necessary to prepare a plurality of texture data corresponding to the number of light sources. However, according to the present embodiment, only one is required, so the trouble of a designer who creates a plurality of texture data is omitted. As well as saving texture memory.

  Another usage example using the texture data of this embodiment will be described. As the value of d increases from 0.0 to 1.0, it is assumed that the gradient gradient is set so that the texture data gradually changes from dark black to light black. The contrast of the shadow can be changed in conjunction with. For example, in FIG. 4, when the coordinate axis is set in the horizontal direction in the drawing and the position of the light source 40 is d = 0.0, the d value changes from d = 0.0 to d = 1.0 as the distance from the light source 40 increases. To do. For example, when d = 0.3, the distance between the light source 40 and the object 50 is relatively short, so that a shadow with a relatively strong contrast is shaded, whereas when d = 0.8, the light source 40 and the object 50 Since the distance is relatively long, shading is performed on a shadow with relatively weak contrast. That is, as the distance from the light source 40 increases, the received light intensity on the object surface decreases in inverse proportion to the square of the distance, and shading processing with weak contrast is gradually performed, so that an effect equivalent to the lighting effect can be obtained.

  FIG. 5 is an explanatory diagram when shading is performed by changing the d value in conjunction with the distance between the camera 60 and the object 50. If the coordinate axis is set in the horizontal direction in the figure and the position of the camera 60 is d = 0.0, the d value changes from d = 0.0 to d = 1.0 as the distance from the camera 60 increases. Here, as the value of d increases from 0.0 to 1.0, it is assumed that the gradient is set so that the texture data gradually changes from dark black to light black. Accordingly, a shading process with a weak contrast is gradually performed, and a fog-like effect can be obtained.

  Note that the present invention is not limited to the case where the d value is changed according to the distance between the light source or the camera and the object and the shading process is performed. For example, the light intensity of the light source can be shaded in association with the d value. For example, the d value is set to 0.0 for a light source having a maximum light intensity, and the d value is gradually increased as the light intensity gradually decreases, so that the d value is increased for a light source having a minimum light intensity. If the value is 1.0, the shadow contrast can be finely adjusted in accordance with the light intensity of the light source. However, in this case, it is assumed that the gradation gradient is set so that the texture data gradually changes from dark black to light black as the value of d increases from 0.0 to 1.0. Further, as an example of setting the d value, the distance between the object and the sea surface can be associated, the distance between the objects can be associated, or other game parameters can be associated.

  FIG. 2 shows another example of texture data. The texture data 30 shown in the figure has a white data area C11, a light gray data area C12, a gray data area C13, and a dark gray color so as to form a curved gray gradient in each of the U coordinate direction and the V coordinate direction. Data area C14 and black data area C15. Equation (1) is used to obtain the U value of the texture data 30 by light source calculation, and Equation (3) is used to obtain the V value. By using the texture data 30, it is possible to adjust the number of shades of shade corresponding to the d value. For example, if the d value is 0.2, the V value takes the value of any one of the data areas C11, C13, and C15, so that the shadow can be ternized, and if the d value is 0.8, Since the V value takes the value of any data area from C11 to C15, the shadow can be converted to five values. FIG. 6 is an explanatory diagram of an application example of shading using the texture data 30. By adjusting the d value in accordance with the points (points) acquired by the player on the game, the shade gradation number is adjusted. ing. In the example shown in the figure, when the number of points is small, the d value is set to 0.2 to set the number of gradations to 3, and when there are many points, the d value is set to 0.8 to set the gradation. The logarithm is 5. Since the number of shades of shadows of game characters, etc. can be adjusted freely in conjunction with the player's acquisition points, the character's atmosphere can be changed freely from anime to dramatic according to the game development. Can be interesting.

  As described above, according to this embodiment, since the color tone of the texture is changed not only in the U coordinate direction but also in the V coordinate direction, for example, it is possible to smoothly paint from a red shade to a blue shade. Therefore, it is possible to change the shade color change naturally without a sense of incongruity. In addition, since the texture for shading is provided in advance as a design, complicated drawing can be easily performed as compared with the conventional continuous change by fog. Conventionally, a plurality of texture data has been prepared corresponding to the number of light sources, etc., but in this embodiment, a plurality of texture data can be aggregated into a single texture data, thereby increasing the cache hit rate. The drawing speed can be increased. Further, since the V value can be specified independently regardless of the luminance I, the data area of the entire texture data can be used effectively, and the texture memory is not wasted.

  In addition, according to the present embodiment, not only the shade tone number and the number of steps, but also highlights appearing in steps, increase / decrease in the amount of reflected light, change in exposure area of the object surface, change in color tone and saturation, change in transparency, etc. Changes can be adjusted freely. In addition, by appropriately changing the d value setting, it is possible to express expressions such as noise, fluctuations in the amount of light that fluctuates when bonfire light strikes, increase or decrease in the area ratio of the shadow part and the exposed part, etc. . Further, by changing the d value for each vertex of the object, it is possible to express a complicated point light source, an expression in which the shadow changes only on a specific part of the object surface, or an expression in which the specific part is glossy. Further, the present invention can be used not only for texture mapping to an object composed of polygons but also for texture mapping for curved surfaces such as NURBS.

It is explanatory drawing of texture data. It is explanatory drawing of texture data. It is explanatory drawing of a texture mapping. It is explanatory drawing of a texture mapping. It is explanatory drawing of a texture mapping. It is explanatory drawing of a texture mapping. It is a functional block diagram for producing | generating a video signal. It is explanatory drawing of texture data. It is explanatory drawing of a texture mapping. It is explanatory drawing of a texture mapping.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Texture memory 12 ... Filter 13 ... Frame memory 14 ... Video signal generation part 20, 30 ... Texture data 40, 41, 42, 43 ... Light source 50 ... Object 60 ... Camera

Claims (3)

In order to access texture data including a computer-readable data area in which different color data is arranged in each of a plurality of areas provided in a two-dimensional plane, a normalized normal vector of an object surface to be texture-mapped, and A coordinate U for accessing the data area in any one of the two directions is calculated based on the luminance value I obtained from the inner product of the standardized ray vectors and the constants a and b. Calculated by the formula U = a * I + b,
The coordinate V for accessing the data area in the other one of the two directions is the distance between the object and the light source, the distance between the object and the virtual viewpoint, the distance between the object and another object, Alternatively, based on the value of the dynamic variable d determined in conjunction with any one of the points obtained by the player in the game performed using the game character having the object surface, the calculation formula V = d Calculate
A texture mapping method in which color data is read out by accessing the data area based on the calculated coordinates U and V, texture mapping is performed on the object surface, and the obtained image data is displayed and output. Computer
In order to access texture data including a computer-readable data area in which different color data is arranged in each of a plurality of areas provided in a two-dimensional plane, a normalized normal vector of an object surface to be texture-mapped, and the value I of intensity obtained from the inner product of the normalized light vector, and, based on the constants a and b, in the one direction of the two directions, the coordinates U for access to the data area, calculated Means for calculating by the formula U = a * I + b ;
Coordinates V for accessing the data area in the other one of the two directions are the distance between the object and the light source, the distance between the object and the virtual viewpoint, the distance between the object and another object, Alternatively, based on the value of the dynamic variable d determined in conjunction with any one of the points obtained by the player in the game performed using the game character having the object surface , the calculation formula V = d Means for calculating,
Means for reading out the color data by accessing the data area based on the calculated coordinates U and V , texture-mapping the object surface, and displaying the obtained image data ;
Program to function as. In order to access texture data including a computer-readable data area in which different color data is arranged in each of a plurality of areas provided in a two-dimensional plane, a normalized normal vector of an object surface to be texture-mapped, and the value I of intensity obtained from the inner product of the normalized light vector, and, based on the constants a and b, in the one direction of the two directions, the coordinates U for access to the data area, calculated Means for calculating by the formula U = a * I + b ;
Coordinates V for accessing the data area in the other one of the two directions are the distance between the object and the light source, the distance between the object and the virtual viewpoint, the distance between the object and another object, Alternatively, based on the value of the dynamic variable d determined in conjunction with any one of the points obtained by the player in the game performed using the game character having the object surface , the calculation formula V = d Means for calculating;
Means for accessing the data area based on the calculated coordinates U and V to read out the color data, texture-mapping the object surface, and displaying and outputting the obtained image data ;
A texture mapping apparatus comprising:

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