   Bitmap Transparency
  Is there a simple way to tell OpenGL to NOT draw a specific color? For example, in SDL you use SDL_SetColorKey to tell it to not draw a particular color in a surface. I''m trying to do some 2D OpenGL programming with sprites and the like, but having a seperate image mask is a nuisance and sloppy, and the images I have don''t have an alpha channel. 
  The easiest way (the following is partly pseudo code): //presume a 24 bit RGB bitmapNewSize = OldSize / 3 * 4;NewData = new BYTE[NewSize];for(i = 0; j = 0; i < OldSize; i += 3, j += 4){NewData[j] = OldData[i];NewData[j + 1] = OldData[i + 1];NewData[j + 2] = OldData[i + 2];if(OldData[i] = R && OldData[i + 1] == G && OldData[i + 2] == B)  NewData[j + 3] = 0;else  NewData[j + 3] = 255;}Then create the texture with GL_RGBA, 4 channels and you should be set to go. I may be forgetting something - spewed this out of my tired brain ;  if you look at nehe''s ipicture code it will show you how to load a bitmap and create a alpha layer masking out a colour..with a bit of work you can get it to mask out any colour or if you wish, I will send you my code which allows you to do just that (plus it has the tga loader aswell)   Jumpman - Under Construction;  Thanks for your replies, although frankly these were the kind I was both expecting and dreading. I guess there is just not a simple way of telling OpenGL to just not draw if the bitmap is a certain color, and instead you have to manually add an alpha channel. I guess that''s to be expected since OpenGL is really a 3D graphics library. Is there any chance that D3D has some simple way of not drawing specific colors? Also, is there any way to make a texture in OpenGL that takes a chunk out of a bitmap, instead of using the whole picture? For example, I have tile sets, but I don''t want to have to slice the tile set into 48 different files. I''m expecting I''ll have to slice it up in my code and then make textures out of each slice, although this is (like adding an alpha channel) inefficent. ;  Heh yep, they''re called texture coordinates =P(0.0f,0.0f) being the top left corner of your texture, and (1.0f,1.0f) being the bottom right corner of your texture. Anything inbetween will allow you to use chunks of a pre-loaded texture using the glTexCoord2f() proc. ;  Yea, except that''s in awkward GLfloat percentage values, rather than actual pixel values, which are more useful. Would glTexCoord2i let me choose parts of the texture by pixel? 