NVIDIA GameWorks Integration

[anonymous_user_7c71c8ec]

@AndrewJSch;309838

I’ve been experimenting with VXGI in BrickGame, and it’s ! I have a few questions/issues though:

I have a yellowish light brick that’s emissive. If I set the material to have omni directional emissive, it gets a bit brighter (not surprising), but also more saturated. Looking at the voxel emissive values in r.VXGI.DebugMode=2, the emissive color looks simply white with the omni directional emissive disabled. I can’t see how that flag should affect the color, so I suspect it’s a bug.

I can’t increase the VXGI map size to 256 (as the PDF says I should be able to) without the VXGI library throwing an error about the texture having too many mip levels. Maybe performance wouldn’t even be acceptable with a larger texture, but I’m making a painful sacrifice on nearby voxel resolution to have GI at larger distances, so I’d like to try it at least…

I couldn’t find what license the integration+library is distributed under. I’d love to be able to post a binary build of BrickGame+VXGI, but AFAICT I’d have to get a license from NVIDIA first. Is that correct?

I think the VXGI support for ambient lighting could be much better with some small changes. The VXGI diffuse ambient looks like it only supports 6 directional colors, and the UE4 integration only exposes one color. It also is set up to mimic faked ambient occlusion, where the occlusion of the ambient term decreases with distance. That’s a useful capability, but I’d like the option to just use the final cone occlusion to attenuate the ambient lighting. The VXGI specular ambient can use a cubemap, but it can’t tint it, which I need for time of day transitions in BrickGame. It would be great if you could just give it a single cubemap+tint, and it would use it for both diffuse and specular.

Finally, I have a large radius for my sun’s cascaded shadow map, and it is always rotating. VXGI seems to be using the last cascade to light the voxels, but not blurring it enough to hide the aliasing. Blurring would help, but a better tradeoff might be to get rid of the cascaded shadow map and just use cone tracing for the direct shadowing. There probably isn’t enough resolution for photoreal stuff, but I think it might work well for BrickGame.

And a few screenshots…

The emissive voxels going white most likely means VXGI is using UNORM8 emittance, i.e. non-HDR, and it gets saturated when it gets brighter. To get best results, we recommend to set bVxgiStoreEmittanceInHdrFormat=true in BaseEngine.ini. option changes the emittance format to FP16 (on ) or FP32 (on other GPUs). You can also experiment with VxgiEmittanceStorageScale option (same location) and see if there’s a setting that looks good with non-HDR in your case.

The error with map size = 256 is a bug in the config validation code; it’s already fixed in the development version, and the fixed DLL should be out with the next release. Performance with such a large map is really poor though.

We certainly can add a tint for the cubemap, and cubemap support for diffuse ambient lighting. I’m not so sure that the ambient term multiplied by final opacity will look well, though, but it’s
easy enough to try.

We also had the idea of using cone tracing instead of shadow maps, and there was an experimental version like that. It was much slower than shadow maps, and the quality was much worse. So I guess we’ll need to improve cascaded shadow map sampling during voxelization.