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LIGHTMAP 14.10.02
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The use of static Lightmaps and Multitextureing, are nice ways to make a 3D world look more realistic.
A lightmap is just a normal texture, but we use it different. Lets say we have a normal floor texture and a
black and white lightmap, when we blend them the black part will have a shadow effect, and the white part
will seem like light. Just like in the pictures below.
Ronny André Reierstads's Easy Baking Recipe..
How to do it step by step...
INSTRUCTIONS:
GENERAL:
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1. Start with a project that can load texture
2. Add the header file "glext.h" to your project
3. Decleare two new function pointers with "NULL" as inital value.
PFNGLMULTITEXCOORD2FARBPROC glMultiTexCoord2fARB = NULL;
PFNGLACTIVETEXTUREARBPROC glActiveTextureARB = NULL;
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4. Declare a texture array that can hold two textures.
INIT:
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5. Activate multitexturing, and define the new function pointers.
glActiveTextureARB = (PFNGLACTIVETEXTUREARBPROC)wglGetProcAddress("glActiveTextureARB");
glMultiTexCoord2fARB = (PFNGLMULTITEXCOORD2FARBPROC)wglGetProcAddress("glMultiTexCoord2fARB");
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6. Load the textures (ID 0 = normal texture, ID 1 = lightmap)
BMP_Texture(TextureArray, "texture/image1.bmp", 0); // Here we load a normal texture
BMP_Texture(TextureArray, "texture/lightmap.bmp", 1); // Here we load a lightmap
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RENDER:
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7. Assign our texture ID, to a new Multitexture ID.
glActiveTextureARB(GL_TEXTURE0_ARB);
glEnable(GL_TEXTURE_2D);
glBindTexture(GL_TEXTURE_2D, TextureArray[0]);
glActiveTextureARB(GL_TEXTURE1_ARB);
glEnable(GL_TEXTURE_2D);
glBindTexture(GL_TEXTURE_2D, TextureArray[1]);
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8. We draw our object and set the UV texture coordinates for our texture, we also
pass in the new Multitexture ID and it's texture coordinates to glMultiTexCoord2fARB.
Notice, that we use both textures on each vertex, this is Multitexturing!
glBegin(GL_QUADS);
// top left vertex
glMultiTexCoord2fARB(GL_TEXTURE0_ARB, 0.0f, 1.0f);
glMultiTexCoord2fARB(GL_TEXTURE1_ARB, 0.0f, 1.0f);
glVertex3f(-1, 1, 0);
// bottom left vertex
glMultiTexCoord2fARB(GL_TEXTURE0_ARB, 0.0f, 0.0f);
glMultiTexCoord2fARB(GL_TEXTURE1_ARB, 0.0f, 0.0f);
glVertex3f(-1, -1, 0);
// bottom right vertex
glMultiTexCoord2fARB(GL_TEXTURE0_ARB, 1.0f, 0.0f);
glMultiTexCoord2fARB(GL_TEXTURE1_ARB, 1.0f, 0.0f);
glVertex3f(1, -1, 0);
// top right vertex
glMultiTexCoord2fARB(GL_TEXTURE0_ARB, 1.0f, 1.0f);
glMultiTexCoord2fARB(GL_TEXTURE1_ARB, 1.0f, 1.0f);
glVertex3f(1, 1, 0);
glEnd();
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The End
Regards.
Ronny André Reierstad
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