Re: How to use the render layer passes.
Posted: Fri Jan 09, 2015 10:31 pm
Regarding the caustics -- yes, the black shadows cancel out the caustics. The black shadows are composed in with the normal layer mode which is alpha blending. Mathematically, alpha blending works like this:
You can change the opacity of the shadows or you can swap the order of the reflection and shadows layer, likely you will have to make the reflections more transparant in this case because they will appear to strong. Like I said, backplate compositing is more of an art than a science so you have to tweak until it looks good subjectively.
cheers,
Thomas
alpha * shadows_pass + (1 - alpha) * background
. This means that indeed where the shadows are fully black (alpha = 1), the background with the reflections on top of it is (1 - 1) or invisible.You can change the opacity of the shadows or you can swap the order of the reflection and shadows layer, likely you will have to make the reflections more transparant in this case because they will appear to strong. Like I said, backplate compositing is more of an art than a science so you have to tweak until it looks good subjectively.
cheers,
Thomas