First Pass Realtime Volumetric Light Scattering

[scrcro (scrcr0)]

@jmarshall23;349867

That is a great idea but the VLS pass is very memory bound as it is, I feel that adding another sampler during the raymarch might not be worth it. Basically during the VLS pass were doing a bunch of random reads into the shadow map texture, so the L2 cache on the GPU is constantly pulling from VRAM, causing whatever wavefront is processing that part of the shader to basically stall, while it waits for data. I do plan on adding VLS “cookie” textures which would just be a alphed texture that would get copied on to the shadow map that would help people carve out various rays without having to make a bunch of geo for it.

There are a couple ideas that would be cheaper; we can calculate 3d noise of the fly based on various parameters, or we can have a VLS only shadow pass that would render all the same geo as the regular shadow pass but would have VLS only geo inside of it. I don’t know if particles currently cast shadows in UE4, but we can maybe get something to work that would get you close to what your looking for.

VLS isn’t ALU intensive so doing 3d noise on the fly might be a viable option.

It doesn’t necessarily need to work with particles. Just being able to multiply the final colour of the VLS with a 3D fractal will suffice.