What I want to achieve is a very “2D, plastic” effect. In other words, I want to layer various things in an “entirely shadow-less way” on top of a plane. And, I specifically want to use the EEVEE render engine (for other good reasons).
I have built the various shapes as meshes which are very close to one another along the Y-axis, backed by a “blue background” plane. Each of them geometrically extend through the plane. However, unless the front-distance is extremely slight, I see “muddy shadows,” where EEVEE seems to be doing shadow calculations between two directly-adjacent parallel planes. How can I tell EEVEE not to attempt to calculate these shadows?
Notice also: these need to be specific characteristics of "the objects on the set." I definitely need “shadows and so-on” elsewhere in the shot. What I am looking for, I guess, is some way to cause EEVEE not to attempt to generate shadows surrounding these very-specific things. “They are plastic.”
If you want to some objects to not contribute to AO, you can change the blend mode from opaque to Alpha Blend. It will then not be added to the depth buffer which is used for calculating AO.
It will also introduce additional problems with depth sorting, which I can’t tell if they would be problematic for you or not without seeing the scene. Most egregious ones will be fixed by disabling “show backface”.
I believe that I found a solution in: Material … Settings … Shadow Mode = “None.”
This, I think, says that “this material doesn’t cast a shadow.” Which is exactly what I want here.
I’m working to construct a very-stylized “cheap-plastic world” for a comedy short, and I want the background to look flat. The overall lighting should also appear flat. Some objects in the foreground should cast shadows, but the elements of the horizon (e.g. “plastic mountains”) should not. The final renderer, on my limited laptop hardware, has to be EEVEE. (Or “Workbench” while deciding what to shoot.)
