View Full Version : Fog problems

12-19-2003, 12:00 AM
Hello everybody

I have been trying to get the build-in fog effect working, as specified in the online version of the Red Book, but I have some problems.

The fog effect only works on one axis (z i presume), so if I turn my camera to look down the x-axis, there is no fog. I am not sure what I am doing wrong here, the docs make it seem very straight forward and simple http://www.opengl.org/discussion_boards/ubb/smile.gif


12-19-2003, 02:29 AM
Im pretty sure you put stuff in the projection matrix that doenst belong there. Only projection should occur in that matrix, the camera rotation/movement should be in the normal Movelview matrix.

12-19-2003, 03:22 AM
And beware, the default fog is almost always computed relative to eye z distance. So when you rotate around, the fog seem to move.

As it is computed per vertex, you need pretty well tesselated geometry too. It depends on the type of fog, though.

I have seem an 3 years old nvidia extension (GL_NV_fog_distance) able to do true radial z computations, used in Return to Castle Wolfenstein.

Else, try a fragment program http://www.opengl.org/discussion_boards/ubb/smile.gif