1. texturing a parametric surface
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 4)
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.

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

11. useful function to read texture data from a .BMP From 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 static unsigned int texture[2];
// Array of texture indices.
// Create texture index array.
glGenTextures(2, texture);
// Struct of bitmap file.
struct BitMapFile{
int sizeX; int sizeY;
unsigned char *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);
GL_TEXTURE_MAG_FILTER,GL_NEAREST);

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