Hey All, I'm currently working on my own implementation of bump mapping and I was using Nehe's lesson 22 as a guide. However I am looking in the function: bool doMesh2TexelUnits(void) and in this function he makes use of: // s-Texture Coordinate Direction, Normalized GLfloat s[4]={0.0f,0.0f,0.0f,1.0f}; // t-Texture Coordinate Direction, Normalized GLfloat t[4]={0.0f,0.0f,0.0f,1.0f}; but I'm not exactly sure what these are. I'm used to specifing texture coordinates using glTexCoord2f where I think of a texture as a flat surface, that has 2 dimensional coordinates. I'm not sure of how to think of these "texture coordinate directions" or even where to begin looking for some more information on them. I'm also not using a square box in my image, so I'm not sure how to set them up. If anyone has any ideas, please let me know! Thanks Danielle