ShaderChunk: Implemented mipped bicubic transmission texture filtering.

[mrdoob]

Description

The current transmission shader technique makes the 0.25-0.75 roughness ranges pretty unusable due to the artefacts.
This PR implements @N8python's shader for sampling the texture using bicubic filtering.

(Left side: bilinear, Right side: bicubic)

Haven't done performance comparisons yet.

[N8python]

Some preliminary performance comparisons on an M1 indicate that the perf hit is negligible - but it may be more noticeable on lower-end devices. If anyone is on an iGPU/Phone, it would be great to see how the performance changes there - as the 7 extra texture reads the shader uses might cost more on such a lower-end platform.

[optimus007]

i have some weak phones , can test if there's live url.

This blurring technique could also be used for scene.backgroundBlurriness right ? low values makes the hdri more blocky in the current version

[N8python]

i have some weak phones , can test if there's live url.

This blurring technique could also be used for scene.backgroundBlurriness right ? low values makes the hdri more blocky in the current version

Depends! If the background is an hdri, definitely. I'm not sure how to apply this to cubemaps, however.

[trusktr]

My intuition would say to make the blur mode be choosable by the end dev.

• a first-person shooter may need low-quality pixelated blur on glass panes in the game env,
• while a glass UI with a lot less things to render would need perfect high quality blur (like CSS backdrop-filter)

Maybe the only sampler size is enough to specify that?

[mrdoob]

Here are a couple of performance test links:

https://mrdoob-sandbox.glitch.me/threejs_transmission_r149.html
https://mrdoob-sandbox.glitch.me/threejs_transmission_r150dev.html

	r149	r150dev
MacBook Air M1	46	45
Pixel 7	70	64

[donmccurdy]

	r149	r150dev
iPhone 11 Pro	60	60
iPhone SE	56	41
iPad Pro (2017)	39	31
Nexus 5x	20	14

+1 for the change. There are some worthwhile challenges in trying to enable MeshStandardMaterial and MeshPhysicalMaterial to "scale down" to low-end devices better, but I don't think keeping the old transmission texture filtering method around is the right approach to solve that.

[Mugen87]

Tested on three devices:

	r149	r150dev
Mac mini M2 Pro	60	60
Lenovo Legion RTX 2070	144	144
Pixel 4a	24	20

[N8python]

Judging by these perf tests, think it is definitely safe to merge :D!