You are mixing up terminology a bunch =)
GI techniques (DFGI, heightfield GI) are for solving bounce lighting, while shadowing techniques (CSM, Ray Traced DF shadows) are for solving direct shadowing.
Direct shadowing recommendations for an outdoor scene:
- Use Cascaded Shadow Maps up to about 20k units (200m). This allows World Position Offset animation and high resolution near the viewer, but it will be very expensive.
- Use Ray Traced Distance Field shadows from 20k units to 100k. These tend to be more efficient when many triangles would have been required, as is the case with many distant trees. However, RTDF shadows don’t support landscape so you need a 3rd method:
- Use Far shadows (FarShadowCascadeCount) for 20k to 1000k. These are just CSM that only include tagged objects with bCastFarShadow set, so the GPU cost is low. By default Landscape will be the only thing included. Note that this overlaps with the RTDF shadow range.
That’s what we did for the Kite demo. It’s a bit of a mess with the far cascades in there, but that’s what we have for now.
With the upcoming (post 4.8) optimizations for DFAO combined with heightfield GI, I think we will be in a great spot for outdoor scenes with fully dynamic lighting. Indoor lighting however needs a lot of work.