HalfFloat PMREM

[elalish]

We've been rendering to HalfFloat textures for several months now for model-viewer's auto-generated environment lighting without complaint, so it seems that at this point HalfFloat texture support is pretty universal (finally!). The only reason I wrote PMREMGenerator to use RGBE internally was because at the time there was not decent floating point rendering support. This made the code complicated and slow because I had to do manual bilinear interpolation (since decode was needed before mixing).

Here I've removed all that by switching PMREM to use HalfFloat internally. I suppose it'll take twice the GPU RAM (16 bits vs 8), but hopefully that's more than offset by skipping a bunch of exponentiation. I've tested on my Macbook Pro and my Pixel 3 and can't see any difference to our glTF renders. I'd appreciate some more device testing, but I'm fairly confident given our widely deployed use of HalfFloat render targets in MV.

@mrdoob @WestLangley

[elalish]

Looks like some problems with the node materials; anyone have any pointers on that? I haven't used those.

[elalish]

Also, does anyone have a convenient performance benchmarking tool for this? I'd be interested to know how much of a difference it makes (primarily to frame rate).

[WestLangley]

/ping @sunag for node

[WestLangley]

So far, the only issue I see is with the webgl_shaders_ocean.html example

before

after

[elalish]

Oh, I think that might be because I removed part of the encodings_fragment that I didn't think anyone else was using. Easy enough to put that back.

[sunag]

/ping @sunag for node

There were some issues this month about NodeMaterial but all related with legacy version, legacy version will be discontinued. I am working on the update. In case of this PR was merged, I can fix some urgent issue about it.

[elalish]

@WestLangley Thanks for noticing that problem; turns out it was not what I first thought. Instead, the toneMapping changed (it's off during PMREM.fromScene()) but the sky shader was not being recompiled because it was not marked as needsProgramChange. I've added this, since it seems like the correct thing to do. Basically this bug was always there, but I used to change several more things during PMREM, which caused the sky to correctly recompile before.

[elalish]

@sunag You can see in the screenshots I updated that this broke something in the pmrem node; seems likely related to the toneMapping issue I found above.

[WestLangley]

@elalish Currently, the webgl_tonemapping.html example sets the material update flag when tone mapping changes:

renderer.toneMapping = toneMappingOptions[ params.toneMapping ];
mesh.material.needsUpdate = true;

Maybe that can be avoided. I'll defer to @Mugen87 regarding the implementation details.

Also, remember to consider the material.toneMapped property.

[Mugen87]

Maybe that can be avoided. I'll defer to @Mugen87 regarding the implementation details.

With @elalish's change to WebGLRenderer, manually setting mesh.material.needsUpdate = true; in webgl_tonemapping should not be necessary anymore.

[mrdoob]

Beautiful! Thanks!

[WestLangley]

As I said, ...

Currently, the webgl_tonemapping.html example sets the material update flag when tone mapping changes:

[mrdoob]

You mean that we still have to remove that line, right?

[WestLangley]

Yes... and that would be a good test that the code changes are working correctly.

And maybe a Migration note would be advisable.

[Mugen87]

@sunag The node examples webgl_materials_envmaps_hdr_nodes and webgl_materials_envmaps_pmrem_nodes using PMREM are still broken on dev:

https://raw.githack.com/mrdoob/three.js/dev/examples/webgl_materials_envmaps_hdr_nodes.html
https://threejs.org/examples/webgl_materials_envmaps_hdr_nodes

https://raw.githack.com/mrdoob/three.js/dev/examples/webgl_materials_envmaps_pmrem_nodes.html
https://threejs.org/examples/webgl_materials_envmaps_pmrem_nodes

Do you think you can fix them before r136 is released?

[sunag]

@Mugen87 Probably yes., I was thinking it release would be in the Christmas,.. I was working in NodeEditor updates, but I will fix first.

[mrdoob]

@sunag you can always check here the date in which every release is due:
https://github.com/mrdoob/three.js/milestones