Blender 2.8; Combine Cycles and Eevee render engines into single composite

Question

I am wondering if it's possible to set up the following scenario: Initiate render -> Eevee render into render layer with specified render settings -> Switch to Cycles render engine with specified render settings (specifically just a free style pass) into a render layer -> Composite using compositor alpha over

Is this currently possible? I saw some solutions for combing Blender Internal and Cycles render passes in 2.79 but I am unsure if this kind of functionality is available in 2.8

My intention is to use this as a work around until freestyle is functional in 2.8.

Thank you

Answer 1

This solution seems to get me 99% of what I originally asked for in the question.

Okay I got it to work, my problem was I was trying to create two different View Layers - create an additional Linked Scene instead so all your objects stay consistent between the two, in compositing make two Render Layer nodes and set each one to the respective Scenes you've rendered. Then you can alpha over the scene with the Freestyle pass and the Eevee pass.

My only problem now is that if I render both the scenes (as in neither has "Use Single Layer" clicked) it takes about 2 minutes for a very simple scene, but if I render them individually (One after another with "Render Single Layer" clicked) they each respectively take a second or two. It seems that when I render them both concurrently the Cycles pass still path traces the objects even with all the passes and ray visibility disabled. Not sure if I am missing something or if this is a possible bug.

Answer 2

So I'm doing something very similar, but I haven't experimented with separate scenes and concurentl renders. I found that reducing my render samples down to 1 for cycles speed up tremendously for line-only freestyle renders in cycles.

Update: I tried your scene technique, but I haven't been able to get Eevee and Cycles to play nicely when using the Shader to RGB node.