UpdateBackGround() and UpdateWorldSettings() is called every frame (necessary if we have multiple scenes running).
So calling KX_GetActiveEngine()->GetRasterizer()->SetFog(...) will be much slower.
May be the best would be to make these variables constant.

It actually wont be that slow to do the calls. Modern processors and compilers handle functions calls pretty well these days. Having the drawtype fixed at construction is particularly problematic, as this does change during execution for shadows.

Do we really need to call into BlenderWorldInfo this much? Can we not just call one update that handles all the bf_gpu calls once per frame per scene?

Are these being called for GLSL mode too? Does GLSL mode use fixed function fog? If not, we should avoid fixed function calls that we don't need. I guess by moving them here we at least avoid calling them every frame, but can we be sure that these state variables are not being screwed up by someone?

OK. I will change that.

Yes the four calls are are necessary. Actually the are only per frame per scene.

1. Is when dome render is enabled.
2. Is for normal render.
3. Is when the stereo mode is enabled.
4. Is for the image texture render.

Yes text objects has no material and without the text will not display with fog.
If sometime someone add a material patch for text objects, we only need to add a check in UpdateWorldSettings().