3 hours ago, Anfaenger said:but its surfel-based GI requires heavy precomputation.
I work on automated tool to generate regular surfel LOD hierarchies and seamless UVs to apply them to the mesh since... >2 years now, so don't use surfels!!!! haha (Especially not with terraforming.) This also means i'm actually focused with geometry processing, and i got rusty with GI. I'm also not up to date with ambient dice, which is interesting but just another new format to to represent the data (you surely know this: https://mynameismjp.wordpress.com/2016/10/09/sg-series-part-1-a-brief-and-incomplete-history-of-baked-lighting-representations/)
But i can mention some lesser known alternatives to tracing on how to calculate GI.
With the cascaded SH grid i tried two methods. The first was Bunnells interesting anti-radiosity trick to avoid expensive visibility determination all together, mentioned on the bottom here: https://developer.nvidia.com/gpugems/GPUGems2/gpugems2_chapter14.html He uses surfels, but it works with volume grid too. Beasically each voxels needs to gather a volume of neighbouring voxels from all cascades. Simple but bandwidth heavy. He tried to make games from the surfels method on last gen consoles. Here a result but it did not became a thing:
You see it is fast and looks good, but the visibility trick causes color shifting bleeding through walls, making it unpractical for complex interiors. He proposed to fix this with labeling rooms, but that's just a hack. For outdoor games however, the approach seems suited very well and i don't know why it has never been used.
The second approach i tried was diffusion. (Similar to Cryteks LPV, but not relying on screenspace) This solves the bandwidth issue, but speed of light becomes noticeable slow. Using a single SH volume also can not represent multiple bounces well - for this multiple volumes, or at least a second one to handle indirect bouncing would be necessary. This seems an example:
The reason i gave up on those things personally was the inability to represent complex interiors with voxel mip maps and resulting leaking for indoor scenes.
Sharp specular reflections are out of reach with any of this, ofc.
8 hours ago, Frantic PonE said:Those are the two major ones I can think of if you don't want to try split cone tracing, or waiting to see if Cryengine explains what they're doing in a readable manner
IIRC, they offer two modes, the cheaper one uses the voxels only for visibility determination, so they could be represented by a single bit. Less memory -> higher res to solve leaking, eventually. I guess it works somehow like this: https://software.intel.com/en-us/articles/layered-reflective-shadow-maps-for-voxel-based-indirect-illumination
13 hours ago, Anfaenger said:But I'm afraid that the cost of tracing the whole scene through several cascades would be prohibitively high,
Maybe it's fast enough
EDIT: I'm optimistic, looking at this for example: http://teardowngame.com/
Seems he does not do anything special: http://blog.tuxedolabs.com/2018/10/17/from-screen-space-to-voxel-space.html