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Texture

Texture. generating textures using textures repeating clamping filtering texturing a parametric surface. Examples of texturing. loadTextures.cpp. where to put the Textures folder.

ljessica
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Texture

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  1. Texture generating textures using textures repeating clamping filtering texturing a parametric surface

  2. Examples of texturing

  3. loadTextures.cpp

  4. where to put the Textures folder • VS: usually in the same folder as the .cpp file. If project is graphics, then in folder graphics/graphics • Xcode: XCodeHowTo link. (class 1) • Unix: in file with executable

  5. Try it now. • First try • loadTextures.cpp from the 1st edition • If the computer complains about glext, just comment out that include in the code. • If you get a white square, call me over. • More errors, see the next two slides, only if I tell you to!

  6. fixing getbmp.cpp • Get the files getbmp.cpp and getbmp.h from the lecture page • in getbmp.cpp, in getbmp.cpp comment out old return and replace with new return: //return bmpRGBA; //mjb return bmpRGB;

  7. fixing loadTextures.cpp • in loadTextures.cpp • comment out the Bitmap struct • comment out the function BitMapFile *getBMPData(string filename) • comment out the function call //image[0] = getBMPData("Textures/launch.bmp"); • and replace with the function call image[0] = getbmp("Textures/launch.bmp");

  8. Format of Texture Big 1-D array: R G B A R G B A R G B A 1st pixel 3rd pixel 2nd pixel

  9. This data is in many photos, but has to be properly retrieved

  10. Book examples use uncom-pressed 24 bit BMP www.tinaja.com/glib/expbmp.pdf

  11. useful function to read texture data from a .BMPFrom 1st edition // Routine to read a bitmap file. // Works only for uncompressed bmp files of 24-bit color. BitMapFile *getBMPData(string filename) • Go through the function • notice BGR vs RGB

  12. If you can't get this version working, there is a new version, with a separate .h and .cpp file, from the 2nd edition. • Links are on the webpage, only if you need it.

  13. Changes to make to loadTextures.cpp from 2nd edition //image[0] = getbmp("../../Textures/launch.bmp"); //mjb image[0] = getbmp("Textures/launch.bmp");

  14. Changes to make to loadTextures.cpp from 2nd edition In main, comment out: glutInitContextVersion(4, 3); glutInitContextProfile(GLUT_COMPATIBILITY_PROFILE); glewExperimental = GL_TRUE; glewInit();

  15. globals and setup staticunsignedint texture[2]; // Array of texture indices. // Create texture index array. glGenTextures(2, texture); // Struct of bitmap file. struct BitMapFile{ int sizeX; int sizeY; unsignedchar *data;};

  16. loadExternalTextures() // Local storage for bmp image data. BitMapFile *image[1]; // Load the texture. image[0] = getBMPData("Textures/launch.bmp"); // Activate texture index texture[0]. glBindTexture(GL_TEXTURE_2D, texture[0]); ... // Specify an image as the texture to be bound with the currently active texture index. glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, image[0]->sizeX, image[0]->sizeY, 0, GL_RGB, GL_UNSIGNED_BYTE, image[0]->data);

  17. loadProceduralTextures() // Activate texture index texture[1]. glBindTexture(GL_TEXTURE_2D, texture[1]); ... • // Specify an image as the texture to be bound with the currently active texture index. glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, 64, 64, 0, GL_RGB, GL_UNSIGNED_BYTE, chessboard);

  18. createChessboard(void) • look at function

  19. texture space • texel : pixel of a texture • note: s, t, intervals [0,1]

  20. mapping a polygon to texture space // Map the texture onto a square polygon. glBegin(GL_POLYGON); glTexCoord2f(0.0, 0.0); glVertex3f(-10.0, -10.0, 0.0); glTexCoord2f(1.0, 0.0); glVertex3f(10.0, -10.0, 0.0); glTexCoord2f(1.0, 1.0); glVertex3f(10.0, 10.0, 0.0); glTexCoord2f(0.0, 1.0); glVertex3f(-10.0, 10.0, 0.0); glEnd(); • Interpolate

  21. other texture maps

  22. interpolates through triangles

  23. repeating

  24. repeating

  25. glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S,GL_REPEAT); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T,GL_REPEAT);

  26. glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S,GL_CLAMP); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T,GL_REPEAT);

  27. fieldAndSky.cpp • run • notice shimmer • try clamping grass in T direction • do graph paper experiment.

  28. Problem with Pixels

  29. GL_NEAREST glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER,GL_NEAREST); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER,GL_NEAREST);

  30. GL_LINEAR glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER,GL_LINEAR); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER,GL_LINEAR); • Average the surrounding points

  31. mipmap • make other versions of texture, various sizes • speed vs storage • book has good examples • if you try mipmaplevels.cpp change to d+=10.0 (not .2, also for -=) Nothing happens till box gets very small

  32. fieldAndSkyFiltered.cpp • run and observe differences

  33. texturing parametrized surfaces

  34. texturedTorus.cpp • run • note code for parametrization • // Specify how texture values combine with current surface color values. glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_REPLACE); • run also DoubletexturedTorusMJB.cpp

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