[QUOTE=TheIncredibleMrEgg;3977]Would I be correct in stating reflecting a 2d texture map is cheaper than reflecting a cubemap or regular specuar? Specular is less predictable, because it’s relies on the lights in the scene, whereas a 2d image reflection is just a consistent faked reflection.
From what I remember, the Source engine does or used to do something like this. I realize at times you’d want both reflections and specular highlights, but if you were just going the cheaper route, I’d imagine a 2d reflection to be the cheapest, no?
I’ve just been working with some shaders, still learning and practicing, and trying to categorize different effects.
Thanks for your valuable input. :nod:[/QUOTE]
Specular is highly predictable, Maybe not very useful when you dont have very many lights though. Specular is just the reflection of the light source.
You can get more mileage from reflection maps because you are encoding more light and light sources into a single function.
Performance can be better although with a 2d reflection you may need to add more code to your shader to control the reflections - 2d doesnt represent 3d enviroments that well (only one hemisphere), if you want different specular powers you would have to bias mips of the reflection to make it more blurry.
Cubemaps can be better for some situations and you could generate them at points in your level - I think source engine does this? Then the result reflections could be representive of the enviroment around you. If you want to go more realistic, then cubemaps are good.
Specular is not cheap itself , so if you do reflections - its good to turn it off (although artists will always insist on everything on!)
Another thing you might want to look at is adding HDR to reflections - this allows your light sources to look much brighter in the relfection than the rest of the world , works very well!
edit (was in a rush before):
I was going to say we normally use cubemaps but sometimes spherical reflections, the latter we use when we want to simulate a large amount of lights in and we dont care about it being physically correct, its amazing what you can get away with!