I have heard that subsurf scattering makes objects look more realistic. Is this true? When should i or should not use it?
Subsurface scattering is the scattering of light THROUGH something as opposed to off of something. You can see this happen the easiest when you hold your hand up to the light and see the light shining through it. Subsurface scattering is pretty much a must for human skin, and adds a lot to really any organic substance, like milk, fruit, wax, or any kind of flesh.
Basically when to use it is usually in the above cases, although it’s possible to get away with it, which saves time. When it’s not used is basically on any hard surface, like diamond, metal, rock or pavement.
Things like ‘wood’ are a touchy subject, because there is a very FAINT amount of subsurface scattering through the fibres, but generally it’s not needed for wood and only wastes time.