[pandaman]

No, branching works on GPU just like everywhere else - the instruction pointer gets changed to another value. But you cannot branch on a vector value unless every element of the vector is the same, this is why branching on vector values is a bad idea. However, if your vectorized computation is naturally divergent then there is no way around it, conditional moves are not going to help as they also will evaluate both branches in a conditional. The best you can do is to arrange it in such a way that you only add computation instead of alternating it, i.e. you do if() ... instead of if() ... else ... then you only take as long as the longest path.

This reminds me that people who believe that GPU is not capable of branches do stupid things like writing multiple shaders instead of branching off a shader constant e.g. you have some special mode, say x-ray vision, in a game and instead of doing a branch in your materials, you write an alternative version of every shader.