Some testing of Raytraced shadows and AO

I only have a 1080 TI, so I wanted to see what could be achieved with as little RT stuff as possible. Here are what I ended up with so far.
I’m quite pleased with the results by just using Ray traced shadows for the sun, and ray traced AO on the post process volume. I also like the trick of using a skylight but turning of shadows for it.

Before/after images. (You can switch between Off, Shadows and Shadows+AO)

Some notes/settings

  • r.RayTracing.Reflections is on by default. Disable it if you’re not using it. (It took quite a bit of fps while doing nothing in my scene)
  • I enabled r.RayTracing.Shadows and r.RayTracing.AmbientOcclusion
  • On the skylight i turned off “Cast Shadows” (I let the post process RT AO handle it)
  • For this scene I set the Post process volume Ambient Occlusion intensity to 1 and samples per pixels to 3.
  • Since Ray tracing is mostly a per-pixel-cost, you get nice results “at any distance” like in this picture:

Some comparisons of default and RT shadows and AO: UE4 DXR - Imgsli

If you like the smoother edges of CSM shadows you can adjust the Source Angle of RT shadows to make them softer: UE4 DXR Shadows - Imgsli