UE5 Early Access is out. I built it on Linux, and built the “Third Person” example, which runs OK. Some minor install problems, reported to Epic.
Haven't built the demo shown in the videos. That requires loading Epic Games' “Launcher” which is Windows-only. It's apparently possible to bash that into working under Wine, but I don't have time to do that right now.
I'm impressed from detail, reflections (they show the shadow of the character, but not the character itself), and the SM approx. soft shadows.
GI is disappointing and very flat. The detail helps it, but with a Cornell Box kind of scene it lacks any beautiful gradients and detail we would expect form diffuse bounces.
Their radiance cache is really simple:
Bounding boxes and probably low res textures on the faces, each texel serving as a probe. This explains some of the missing detail, but walls are boxes too, so it's a good representation for that, and still i can't see expected detail e.g. AO alike darkening in corners.
Still good enough for a generational leap.
Interesting: DXR is supported, but much slower than object SDF + compute and no visual win.
I think DXR is slow because UE5 scene composition requires heavy overlap of models.
With SDF, you can select a single model simply by taking the one with the smallest distance on ray entry.
With BVH you have to fully trace all models for the closest hit to find the closest one, and this kills DXR performance i guess.
So beside the high res geometry this might be primary reason UE5 and HW RT won't work well together.
That's a big advantage for SDF, not obvious to me before.
If anyone with source access takes a look at how Nanite works, let us know :D
(Can't login to github anymore myself)
…it was very hard to convince github i'm a real human and no robot, but i did it.
Peeked into Nanite compute shaders, but i see more details than the overall idea ofc.
Seems a BVH over triangle clusters, with presistent threads doing traversal, culling and appending to SW / HW rasterizers worklists. Seeing the software rasterizer gives nostalgic feelings. : )
Occlusion culling is done with (probably reprojected) Z pyramid form previous frame i guess. Did not notice any fancy front to back occlusion algorithm as i had assumed.
Feels very scalable. Insane detail is possible, but not necessary.
Very good work to me. One more moving away from the brute force methods relying entirely on hardware which dominated games for much too long.
Looks like no Nanite on Linux yet. Unreal Editor puts up an error message saying that the GPU (NVidia 3070) or the driver isn't acceptable. Put note on Epic feedback board.
From a briefe look into the source code, it doesn't look too much different from the latest UE4 release except that they improved UBT, but still using C# files as their build targets. We'll have a deeper look into it if the first stable release is out and we start working on our new engine core, never ever can have too many resources to steal ideas from ?
