KR20060073814A - Lightmap processing method in 3 dimensional graphics environment and apparatus therefor - Google Patents

Abstract

Disclosed are a light map processing method and apparatus in a three-dimensional graphics environment. A light map processing method according to the present invention comprises the steps of obtaining information about a light source and an object disposed in a three-dimensional graphics environment, generating a light map for an object based on such information, and displaying the generated light map. Mapping to the phase. Before navigation on the 3D environment, the lightmap, which is a collection of textures corresponding to each side of the object, is created in advance, and when the navigation is performed in real time, the lightmap is mapped to the screen, thereby creating a high quality real-time 3D graphics screen. You can get it.

Description

Lightmap processing method in 3 dimensional graphics environment and apparatus therefor}

1 is a diagram illustrating ray tracing.

2 is a diagram illustrating a process of processing a dynamic light map.

3 is a diagram illustrating a process of processing a static light map.

4 is a diagram illustrating each step of a method of generating a light map.

5 is a diagram illustrating packing of a light map triangle.

6 is a diagram illustrating a bounding box.

7 is a diagram illustrating a texel configuration of a bounding box.

8A and 8B illustrate a method of packing a bounding box.

TECHNICAL FIELD The present invention relates to the processing of image data, and more particularly, to a method and apparatus for processing a light map for an object in a three-dimensional graphics environment.

In order to reproduce high quality 3D graphics data in a general computing environment, various techniques for expressing the effects of light are required. How the light from the light source enters, reflects and looks in the plane of the object depends on the technique of expressing the effect of the light.

Graphics techniques that represent the effects of light, ie lighting operations, include Gouraud shading, Phong shading, ray tracing, and radiosity.

1 shows ray tracing as one of the lighting operations. Referring to FIG. 1, general lighting operations such as pong shading, ray tracing, and illuminance calculation are methods of calculating color values for all pixels on a screen, which is complicated and time-consuming. Although they express the effects of light well, the number of operations required increases exponentially as the number of polygons increases. Therefore, it is difficult to use a 3D graphics environment in real time and is used for non real time applications such as animated movies.

The lighting operation used in the real-time three-dimensional graphics environment is Gouraud shading. Sphere shading is a method of smooth shading, in which the lighting operation is performed directly on the polygon's vertices using the normal vector of the vertices, and then the surface color inside the polygon is calculated. This is obtained by interpolating the color change from the color of. It's the simplest and fastest of the smooth shading methods, so it's often used as a shading method that shows the shape of the object you're working in. On high-end graphics workstations, the guillo-shading algorithm can be implemented in hardware to improve speed. The disadvantage is that the edge borders of each polygon are visible. It is especially softer and awkward in areas where highlights on the surface of the object form. Therefore, there is a demand for a method that can obtain a high quality screen while realizing a 3D graphics environment in real time.

An object of the present invention is to provide a method and apparatus for processing a light map, which is a kind of texture, in order to realize a high quality 3D graphics environment in real time.

In order to achieve the above technical problem, a light map processing method in a three-dimensional graphics environment according to the present invention comprises the steps of: obtaining information about a light source and an object disposed in the three-dimensional graphics environment; Generating a light map for the object based on the information; And mapping the generated light map onto a screen.

In order to achieve the above technical problem, the light map processing apparatus in the three-dimensional graphics environment according to the present invention, the light map generation information processing unit for obtaining information about the light source and the object disposed in the three-dimensional graphics environment; A light map generator configured to generate a light map for the object based on the information; And a light map mapping unit for mapping the generated light map onto the screen.

Hereinafter, a light map processing method and apparatus in a 3D graphics environment according to the present invention will be described in detail with reference to the accompanying drawings.

2 and 3 are views illustrating a light map processing process according to the present invention. FIG. 2 illustrates a process of processing a dynamic light map, and FIG. 3 illustrates a process of processing a static light map.

A lightmap is a collection of textures generated by performing a lighting operation on each triangle constituting an object. The present invention provides a method of generating a light map for each object in order to implement a high quality 3D graphics environment in real time and displaying the light map on the screen when the navigation is performed in the actual 3D graphics environment.

The dynamic light map refers to generating such a light map in preparation for navigation and displaying it on the screen during navigation. Referring to FIG. 2, the dynamic light map processing includes executing a navigation program 10, parsing a scene file including information about a three-dimensional graphics environment to be navigated (20). ), Generating a lightmap for the object based on the information about the 3D graphics environment (30), storing the generated lightmap in memory (40), and mapping the generated lightmap on the screen. Step 50 is performed.

The static light map means that the light map is generated before the real-time navigation program is executed, and only the generated light map is displayed on the screen when the actual navigation program is executed. Although static light maps and dynamic light maps have a time difference between when the light map is generated before the execution of the navigation program and the preparation phase of the navigation program, the light map is generated in real time before the actual navigation is performed. When performing navigation, it has a common technical feature in that it only maps a light map to the screen.

Referring to FIG. 3, a process of processing a static lightmap may include applying a light effect using an external graphics tool (100), and generating a lightmap for an object using the light effect. Step 110, generating a scene file including information about the object and the light map corresponding to it (120), starting a navigation program (130), parsing the scene file and information about the object and light map Obtaining 140, reading the lightmap stored in the memory 150, and mapping the lightmap onto the screen 160.

The static lightmap is a method used when the position of the light source and the object does not change in the 3D graphics environment, for example, when a player navigates the 3D environment and performs a mission.

If the relative positions of objects and light sources in the three-dimensional environment change each time the program is run, dynamic lightmaps should be used. When creating a dynamic light map, the light map is generated and stored only when the first navigation program is executed, that is, when the object is loaded. In a subsequent navigation process, the object is created on the screen using the generated light map. Because of the display, it is possible to provide a high quality three-dimensional graphics screen in real time.

Instead of repeating the lighting operation each time the object is displayed on the screen, the lighting operation is performed only once based on the information about the light source and the object placed in the 3D graphics environment before the scene file is generated or when the program is loaded. Since it is performed, general lighting operations such as pong shading, ray tracing, and illuminance calculation can be used for all the pixels on the screen.

One of the methods used to define a 3D graphics environment such as navigation is to implement a scene file using the Virtual Reality Modeling Language (VRML). The present invention proposes a method of defining information related to a light map on a scene file in order to use the light map in a 3D graphics environment.

In order to use lightmap in 3D graphics environment, we define lightmap node. An embodiment of defining a light map node is shown in Equation 1.

Referring to Equation 1, in order to define a light map, information about a light source (affecting light field) to be used when generating a light map, an actual texture memory to store a light map for representing an object It contains information such as the size (textureSize field), the size of a texel in the lightmap in the actual three-dimensional graphics space (texelSize field), the minimum value of the lightmap image (minNumTexels), and the maximum value of the lightmap image (maxNumTexels). It is preferable.

In the embodiment of Equation 1, the affectingLight field defines a list of light sources to be used when generating the light map. If this field has a value of NULL as in the embodiment of Equation 1, all light sources defined in the current scene file affect the generation of the light map of the object.

The textureSize field indicating the size of the actual texture in which the light map is to be stored is defined to have a value between 8 and 2048 in the example shown in Equation 1. For example, when the value is 256, as in the example of Equation 1, the light map for the object is stored in a texture having a size of 256 X 256 pixels.

A texelSize field indicating a size occupied by a texel of the light map in the 3D graphics space has a value in meters in the example of Equation 1. In the case of 0.5, as in Equation 1, one texel occupies 0.5 meter in the real space. This is related to the precision of the lighting operation. In other words, if the value of the texelSize field is large for the same object, a small light map of sparse shape is generated. If the value of the texelSize field is small, a large light map of dense type is generated. In general, the smaller the value of the texelSize field is, the more accurate texture can be obtained. However, if the value of the texelSize field is smaller than necessary, the waste of memory can be increased. Therefore, it is required to set the value of the texelSize field appropriately. The texelSize field may be set for each object or globally for the entire scene. If the texelSize field for each object is not set separately, the texelSize value for the entire scene is used.

The minNumTexels field, which represents the minimum value of the lightmap image, limits the size of the smallest image as a result of the lightmap calculation. As a result, the image generated as a result of the calculation of the light map should be at least larger than the value of the minNumTexels field. This is to prevent the image quality if the lightmap calculation results in a texture space that is too small. If the calculation result of the lightmap is smaller than the value of this field, the value of one texel occupies in the 3D graphics space is reduced to less than the value given in the texelSize field so that the lightmap is larger than the value of the minNumTexels field.

The maxNumTexels field, which represents the maximum value of the lightmap image, limits the size of the largest image generated as a result of the lightmap calculation. As a result, the image generated as a result of the calculation of the light map should be at least smaller than the value of the maxNumTexels field. This is to prevent the image quality when the result of calculation of the light map occupies too much texture space, but the memory efficiency is reduced by occupying too much memory. If the calculation result of the lightmap is larger than the value of this field, the value of one given texel in the 3D graphics space is increased by the value given in the texelSize field so that the size of the lightmap is less than or equal to the value of the maxNumTexels field.

4 is a diagram illustrating each step of a method of generating a light map.

Referring to FIG. 4, in the method of generating a light map, first, a triangle constituting one side of an object is selected (200), and a light map triangle is generated for each side (210). Check whether the size of the generated lightmap triangle is larger than the value of the minNumTexels field (220), and if the size of the lightmap triangle is smaller than the value of the maxNumTexels field (230). If both conditions are satisfied, the lightmap triangle is stored (250). . If the size of the lightmap triangle is less than the value of the minNumTexels field or greater than the value of the maxNumTexels field, the value that the texel occupies in three-dimensional graphics space is increased or decreased above the value given in the texelSize field to satisfy the given condition. 240). After you have created and saved the lightmap triangles, you need to pack them.

5 is a diagram illustrating packing of a light map triangle. In the state where the light map triangles are stored in the memory as shown in FIG. 5A, the memory is inefficiently used. Therefore, it is necessary to efficiently use the memory by packing the light map triangles as shown in B of FIG. 5.

A bounding box is created to pack the lightmap triangle (260). 6 shows a bounding box for packing light map triangles.

Referring to FIG. 6, the bounding box refers to a rectangle that circumscribes the light map triangle and occupies the smallest area. To create a bounding box, create a bounding box with the longest side of the lightmap triangle. In the example of FIG. 6, the triangle is rotated and the bounding box is generated so that the longest side of the triangle is disposed in the v axis direction from the origin.

Note that when creating a bounding box, the bounding box should be designated as 2 to 3 pixels wider than the actual lightmap triangle. An embodiment of a texel configuration of the bounding box is shown in FIG. 7.

Referring to FIG. 7, the bounding box corresponding to the light map triangle includes a temporary texel portion and a useful texel portion. Temporary texels do not perform lighting operations and are not used for texture mapping. A useful texel is a texel that obtains a color value through a writing operation.

Setting the useful texel for a wider area than the actual lightmap triangle and getting its color value is due to the way we map textures. When calculating color values, only the pixel at the center of each texel is calculated. When mapping a texture, the color values of the pixels constituting each texel are displayed by interpolating the color values of the center pixels of the texels around the pixel. However, if there is no color value for the area outside the boundary of the triangle, it is impossible to interpolate the color value. Therefore, in order to calculate the color value of the boundary part, the useful texel is designated wider than the boundary of the original triangle.

The use of bounding boxes in packing lightmap triangles is to apply an algorithm that divides the space into rectangles. This is illustrated in FIGS. 8A and 8B.

8A is a diagram illustrating the allocation of the bounding box 1 to a memory. First, the upper portion is divided by the length of the vertical side of the bounding box 1, and each divided portion is placed as a child node of the dividing line A. The left end is divided by the length of the horizontal side of the bounding box 1 at the upper end of the divided parts, and each divided part is placed as a child node of the dividing line B. At this time, the dividing line B becomes a child node of the dividing line A. Bounding box 1 is also placed as a child node of the dividing line B. Each blank area is leaf nodes, shown as dots in FIG. 8A, which store the lengths of the horizontal and vertical sides of the corresponding blank area. Having all the partitioning process in a binary tree structure like this makes it easier to find empty space to pack the next bounding box.

8B shows packing bounding box 2 to a memory. In the packing state of FIG. 8A, a blank area into which bounding box 2 can be found is found. This is easily done by searching each leaf node sequentially and comparing the length of the longitudinal and transverse sides of the bounding box with the length of the longitudinal and transverse sides of each blank area.

In FIG. 8B, the length of the vertical side of the bounding box 2 is too long to enter the empty area of the upper end of the child node of the dividing line B. Therefore, the bounding box 2 is packed in an empty area of the lower end of the dividing line A, which is the right leaf node of the leaf corresponding to the dividing line A. First, the left end of the empty area is divided by the length of the horizontal side of the bounding box 2, and each divided part is placed as a child node of the dividing line C. Bounding box 2 is assigned to the left side of the dividing line C, and an empty area is allocated to the right child node of the dividing line C. The upper portion of the area corresponding to the left child node of the dividing line C is divided by the length of the vertical side of the bounding box 2, and each divided portion is placed as a child node of the dividing line D.

By repeating the step 270 of packing the bounding box as described above, all light map triangles corresponding to the packed bounding box can be packed.

After the lightmap triangle is packed in memory, the lighting operation is performed on each texel to generate a lightmap. Uv coordinates are calculated for each texel (280), world coordinates are calculated (290) in an actual 3D environment, and a texture is generated by performing a lighting operation for each texel (300).

The high-quality three-dimensional graphics screen can be obtained by displaying the generated light map on the screen in real time through a texture mapping method. The light map processing method and apparatus may be applied to virtual reality, games, mobile graphics, and the like.

The present invention can be embodied as code that can be read by a computer (including all devices having an information processing function) in a computer-readable recording medium. The computer-readable recording medium includes all kinds of recording devices in which data that can be read by a computer system is stored. Examples of computer-readable recording devices include ROM, RAM, CD-ROM, magnetic tape, floppy disks, optical data storage devices, and the like.

Although the foregoing description has been focused on the novel features of the invention as applied to various embodiments, those skilled in the art will appreciate that the apparatus and method described above without departing from the scope of the invention. It will be understood that various deletions, substitutions, and changes in form and detail of the invention are possible. Accordingly, the scope of the invention is defined by the appended claims rather than in the foregoing description. All modifications within the scope of equivalents of the claims are to be embraced within the scope of the present invention.

According to the light map processing method in the 3D graphics environment according to the present invention, before performing the navigation on the actual 3D environment, the light map, which is a collection of textures corresponding to each side of the object, is generated in advance and performed in real time. By mapping the light map to the screen, a high-quality real-time three-dimensional graphics screen can be obtained, and through this, the high-quality three-dimensional graphics environment such as virtual reality, games, and mobile graphics can be realized.

Claims (19)

(a) obtaining information about the light source and the object disposed in the three-dimensional graphics environment; (b) generating a light map for the object based on the information; And and (c) mapping the generated light map onto a screen. According to claim 1, wherein the step (a), And parsing a scene file including information about the three-dimensional graphics environment. The method of claim 2, wherein the scene file, Information about the light source; A size of a texture in which the light map to be generated is stored; A size occupied by a texel of the light map to be generated in a three-dimensional graphics space; A minimum value of the size of the lightmap image to be generated; And And a maximum value of a size of the light map image to be generated. According to claim 1, wherein step (b), (b1) generating and storing light map triangles for each surface of the object; (b2) generating a bounding box for the lightmap triangles to pack the lightmap triangles; (b3) generating a texture by performing a lighting operation on each of the light map triangles; And (b4) storing the generated texture in the light map triangle. The method of claim 4, wherein step (b2), And generating a bounding box having the longest side of the lightmap triangle as one side. The method of claim 4, wherein step (b2), And generating a bounding box including a 2 pixel or 3 pixel wide area outside the boundary line of the light map triangle. The method of claim 4, wherein step (b2), Generating a binary tree having a node corresponding to the entire memory area in which the bounding box is to be stored as a root node; Searching for a node corresponding to an empty space having a size in which the bounding box can be stored on the binary tree; Allocating the bounding box by dividing the empty space vertically or horizontally; And And assigning a node corresponding to the dividing line of the empty space and the bounding box to generate a node corresponding to the newly created empty space and assigning the node to a child node of a node corresponding to the empty space. How to handle lightmaps in 3D graphics environment. The method of claim 4, wherein step (b3), A method of processing light maps in a three-dimensional graphics environment, comprising: generating a texture by performing one of phong shading, ray tracing, or radiosity. The method of claim 1, wherein step (c) comprises: And parsing a file including information on the object and a light map corresponding to the object. A light map generation information processing unit for obtaining information about the light source and the object disposed in the 3D graphics environment; A light map generator configured to generate a light map for the object based on the information; And And a light map mapping unit for mapping the generated light map onto a screen. The method of claim 10, wherein the light map generation information processing unit, And a scene file parser configured to parse a scene file including information about the 3D graphics environment. The method of claim 11, wherein the scene file, Information about the light source; A size of a texture in which the light map to be generated is stored; A size occupied by a texel of the light map to be generated in a three-dimensional graphics space; A minimum value of the size of the lightmap image to be generated; And And a maximum value of a size of the lightmap image to be generated. The method of claim 10, wherein the light map generation unit, A triangle generation storage unit which generates and stores a light map triangle for each surface of the object; A triangular packing unit generating a bounding box for the light map triangles to pack the light map triangles; A lighting operation unit configured to generate a texture by performing a lighting operation on each of the light map triangles; And And a light map storage unit for storing the generated texture in the light map triangle. The method of claim 13, wherein the triangular packing portion, And a bounding box generator configured to generate a bounding box having the longest side of the lightmap triangle as one side. The method of claim 13, wherein the triangular packing portion, And a bounding box generator configured to generate a bounding box including a 2 pixel or 3 pixel wide area outside the boundary line of the light map triangle. The method of claim 13, wherein the triangular packing portion, A binary tree generation unit generating a binary tree having a node corresponding to the entire memory area in which the bounding box is to be stored as a root node; A node searching unit searching for a node corresponding to an empty space having a size in which the bounding box can be stored on the binary tree; A bounding box arrangement for dividing the empty space vertically or horizontally to allocate the bounding box; And And a node generator for generating a node corresponding to the newly created empty space by allocating a node corresponding to the dividing line of the empty space and the bounding box and assigning the node to a child node of a node corresponding to the empty space. Light map processing apparatus in a three-dimensional graphics environment. The method of claim 13, wherein the writing operation unit, And a high quality computing unit for generating a texture by performing one of Pong shading, ray tracing, or illuminance calculation. The method of claim 10, wherein the light map mapping unit, And a mapping information parser configured to parse a file including information on the object and a light map corresponding thereto. Obtaining information about the light source and the object disposed in the three-dimensional graphics environment; Generating a light map for the object based on the information; And A computer-readable recording medium having recorded thereon a program for causing a computer to execute the step of mapping the generated light map onto a screen.

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