This has been a requested feature for… I don’t even know how long. Yes there are GPU offscreen hacks and workarounds that have been developed over the years, but I really wanted a true first-class solution to the problem of live Render from camera > material. This is standard functionality in Godot, Unreal, Unity - why not Blender?
I targeted EEVEE only, and specifically just a color and lighting pass for initial tests. Edited EEVEE source code in my personal sandbox dev build of Blender, made a custom node to pass this to materials.
There are some kinks and performance metrics I need to get a handle on, but wanted to share this teaser.