Hi,
I started investigating this and unless I’m misunderstanding something, I think this use case could be handled by enabling Custom Depth on the meshes which require ray marching. This will write depth info for only those meshes to a separate buffer which can be sampled in a custom half-resolution post-process pass. There is also a property called “Allow Custom Depth Writes” within “Translucency”, setting it to true will compile additional shaders to enable custom depth.
To render the effect at half resolution, there are multiple ways to achieve that (for examples, see this thread):
- user scene textures (save the scene texture to a temporary render target which supports downscaling and use it as an input for further post processing)
- modifying the usf shader (some examples are linked here by following the Github branch links)
- modifying engine source
Some more info on using Custom Depth (and different use cases) can be found at this link: https://www.tomlooman.com/the-many-uses-of-custom-depth-in-unreal-4/
Would this approach work for your case?
Best,
Sam