Is Coronas AO really AO?
Hello forum, the thing is, Coronas AO renders even on directly lit surfaces. This is not how AO should behave, it should pop up only in shadows.
It works great for dirtying things up (and should keep working like that, it’s a useful feature!), but then it should be renamed in “Dirt map”, or something.
Or am i missing something?
Yes, AFAIK you missed something : )
AO is not about light (direct/indirect). AO is basically about distance to other surfaces. In that way Corona AO acts like mr AO.
Nope, in Mental ray AO does not happen on directly lit surfaces.
EDIT: even in Mental it’s there on directly lit surfaces but WAY less then those in shadows. Creating something like this with mental is impossible, especially when objects creating AO are so small (i mean these little things barely protruding from bigger polygons).
Which is what i always use, and probably, hence, the confusion.
You are sort of correct though. The way AO is used in game engines today (like Uncharted series thanks to John Hable), is to fake contact shadows in indirect/ambient lit spaces. It thus makes no sense to use in directly lit, since those already have direct shadows that provides enough contact/grounding (unless they’re too miniscule to be captured, thencavity map is used instead in shader).
No one sensible should be using AO in such way (diffuse overlay in beauty pass) in modern ray-traced engine, though people simply still do. So ‘dirt map’, is imho more valid name. (just like in Vray)
the naming is kinda arbitrary, but so is calling it “dirt”. There is no need to change it, really