Intensity driven Ambient Occlusion in Photoshop (MentalRay)
I’ve got an interesting idea about improving ambient occlusion accuracy which i recently tried in practice and it worked, so i decided to write it down for anyone who may find it useful.
I will try to explain both the issue and the solution.
In MentalRay we have multiple choices of AO solutions:
- Ambient/Reflective Occlusion map
- AO built in Arch&Design material
- AO built in Arch&Desing material with Color Bleed enabled
The first 2 solutions are almost same, with only difference that the first one is a map, the second one is a material feature. They both create fake indirect illumination shadows based on environment being occluded by surrounding objects . Third solution on the other side, doesn’t just fake indirect illumination shadows, but actually samples surrouding objects and environment for color and light intensity information, and then uses these data to create accurate indirect illumination shadow detail.
This picture should give you a better idea of what i am talking about:
As you can see, AO with color bleed offers most accurate solution, but unfortunatelly, it increases rendering time a lot (from my experience by about 40%).
While i was looking for a solution with optimal speed/accuracy ratio, i realized that on most of the images bright areas usually represent highlights and dark areas represent shadows. So i came up with idea, that i could use this intensity information to drive AO behaviour.
I used basic beauty pass as a mask channel to mask out AO pass so i get portion of AO that will be substractive (darkening) using multiply mode. Then i inverted both mask and another AO pass on another layer so i got an additive (brightening) portion using screen mode. › Continue reading
