Mihai wrote:This doesn't make sense to me, I thought IES simple tells how the light spreads, but can you have an IES which specifically gives out say 1300 lumens? And if it does, how do you know the light levels in a scene would be accurate in a renderer like finalrender, or mentalray?
I can't speak with any finality on the subject, he has several more years experience than I, but yes, the IES file tells how the light spreads out. As far as 3DS Max goes, you give it a luminosity in say lumens, and then specify the file to use. So this would seem to me to say that it sends those "1300" lumens in the directions based on the file.
What if you mis-model the reflector in the light or worse; don't have enough pictures/prints to model the reflector. How acurate is that?
And as for the light levels being accurate, no matter what render you use it's going to be an aproximation (until that tool that perfectly measures the BSDF or a material can be used with Maxwell) because the materials are as close as you can get. I guess if you have really good materials in finalRender or MetalRay it would bounce the light appropriately, just like Maxwell (but not as well).
I guess the point is, no, IES can't be as perfect as modeling the lamp, bulb, and reflector, but if you don't have enough information/time to do that, it's alot better than just guessing. Again, this is all my guess/opinion...
