Hi @Fyrestar!
An update on progress:
We got awesome performance increase (we are developing “mobile first”) by rendering Scene 1 containing complex model / animation into a renderTarget.texture and applying it to a plane placed inside Scene 2 as background.
This tutorial was very usefull: Three.js Render Targets
All we have to do now is properly fit the plane to the camera / device-screen, I hope this will nail it (thanks again for finding it):
… and tweak the background-plane texture / material as it looks a bit dull (low color / contrast) at the moment.
We will post the result and a short solution description as soon as we are 100% sure this approach meets our needs.
One more thing:
As we’re now using only one renderer, we can also use the same reflection-material / environment map in both scenes.