NVIDIA GameWorks Integration

[anonymous_user_7c71c8ec]

So with r.VXGI.range being removed and replaced with r.VXGI.MapSizeX (any Y,Z)… Performance kinda stinks. What I mean is, to get lighting in a respectable range, you have to crank that up. As soon as you have a map size of 128 or higher, poof, there go your frame rates. I’ve juggled between various settings combos with r.VXGI.MapSize and r.VXGI.VoxelSize. With a respectable frame rate of ~60 in a basic scene with a single directional light blasting through windows (demo scene from volumetric lighting), I’m using a map size of 64 and a voxel size of 64. Lighting only seems effective at around 40 meters. It goes dark beyond that.

Are there any magic numbers to tweak that won’t effect performance too much? I know I’m dreaming, but hoping I’m just missing/forgetting something! That quality is acceptable with those current settings for an interactive game scenario, but I’d like to lower the voxel size a bit. Of course, when you do that, the distance of lighting drops drastically. I’m afraid of raising diffuse tracing intensity, because it might blow out other things in the PBR pipeline. I’d rather not have to change the typical way of authoring assets.

[edit]

Derp on my part- even if one cranks up the diffuse indirect lighting intensity, it has no effect on lighting distance.

Also, I came across thread over at Nvidia:
https://devtalk.nvidia/default/topic/1031155/general-graphics-programming/vxgi-fallback-diffuse-ambient-color/

Is it possible to wrangle up in a material?

Let me clarify the meaning of these parameters and how they relate to the old r.VXGI.Range.
r.VXGI.VoxelSize is the size of the smallest voxels, in world units. Increasing that will directly increase the range, and slightly degrade performance because more objects now fall into the voxelized region.
r.VXGI.MapSize{X,Y,Z} is the number of voxels on each side of every voxel clip-map volume. It also directly affects the range, but increasing MapSize will make performance much worse (as you observe) as the GPU has to deal with more voxels. Increasing all of MapSizeX,Y,Z by a factor of 2 multiplies the total number of voxels by a factor of 8.
r.VXGI.Range (which is gone) was just a product of MapSize and VoxelSize.
r.VXGI.StackLevels controls the number of clip-map levels (or cascades) in the voxel volume, so setting it 1 higher makes the distance 2x longer; the and default value for StackLevels is 5.

Total world distance covered by VXGI can be calculated as MapSize * VoxelSize * pow(2, StackLevels-1).

Regarding that “fallback color” topic you mentioned: it’s possible to use that in a post-process material. But in 2.0, the confidence value is stored in FScreenSpaceData.VxgiConfidence, instead of VxgiDiffuse.a.