On Tuesday 06 March 2007 00:25, Bas van Dijk wrote:
I am using HOpenGL in combination with hsSDL (http://darcs.haskell.org/~lemmih/hsSDL). This works great except for texture loading. All my textures are mirrored over the v-axis. So the top of a texture becomes the bottom. I first thought that I got the texture coordinates wrong. But the textures are also flipped on the GLU quadrics.
IIRC, in SDL the y-coordinate increases when going down the screen, while OpenGL uses the usual mathematical convention of y increasing when going up. Therefore your images are flipped, I guess.
Is there some way to tell (H)OpenGL that a texture is mirrored? I tried glPixelStore parameters but I don't think it is possible that way. Perhaps it is possible to change a hsSDL surface before loading the pixel data. Any advice is welcome.
Usually the easiest and most efficient way is to simply flip your t texture coordinate, i.e. use 1-t instead of t. Using pixelStore should be possible, too (using negative offsets etc.), but often this is not really needed. Cheers, S.