Improve MeshPhysicalMaterial transmission support Part2

[takahirox]

Related issue: #21884 (comment)

Description

This PR improves MeshPhysicalMaterial transmission support.

@WestLangley Looking good now?

Changes

1. In the previous PR I first applied transmission to diffuseColor

https://github.com/mrdoob/three.js/blob/r129/src/renderers/shaders/ShaderChunk/transmission_fragment.glsl.js#L30

and then applied lighting to it. This is the main reason why the color was darken even if transmission is 1. In this PR I apply the transmission after the lighting.

2. In the previous PR, I calculated specular in the transmission function. But specular is calculated in the lighting. I speculate I can reuse it.

https://github.com/mrdoob/three.js/blob/r129/src/renderers/shaders/ShaderChunk/transmission_pars_fragment.glsl.js#L80-L82

3. I turn off tone mapping for the first opaque objects pass to avoid to apply it again in the second transmissive objects pass.

Screenshots

I still have an issue that multi sample render target is black in the screenshots. So I made the screenshots by temporarily changing the code to non-multi-sample render target. Please feel free to update the screenshots if you can make correctly.

[mrdoob]

I still have an issue that multi sample render target is black in the screenshots. So I made the screenshots by temporarily changing the code to non-multi-sample render target. Please feel free to update the screenshots if you can make correctly.

Have you tried running npm update inside the test folder?

[WestLangley]

Now that it is looking better, we need to figure out how to properly deal with premultipliedAlpha -- when to use it, and when not to.

For a later PR, of course.

[WestLangley]

Also, _transmissionRenderTarget should not be UnsignedByteType, because that leads to clamping and texture hue shifts.

Perhaps UnsignedByteType can be a fall-back if HalfFloatType is not supported.

UnsignedByteType

HalfFloatType is mostly better :-)

[takahirox]

@mrdoob

Have you tried running npm update inside the test folder?

Ah, I didn't notice that I needed to run it in the test directory. Updated the screenshots, thanks!

@WestLangley

Also, _transmissionRenderTarget should not be UnsignedByteType, because that leads to clamping and texture hue shifts.

Perhaps UnsignedByteType can be a fall-back if HalfFloatType is not supported.

Good catch. Updated, thanks!

[mrdoob]

Excellent! Thanks!

[mrdoob]

Oh! Actually... I guess we should also set outputEncoding to LinearEncoding?

[takahirox]

No because we use renderTarget texture's encoding as output encoding if currentRenderTarget isn't null. (Texture's default encoding is linear.)

https://github.com/mrdoob/three.js/blob/r129/src/renderers/webgl/WebGLPrograms.js#L174

If we will start to copy the framebuffer we will need to convert from sRGB to linear and from tone mapping to none in the shader if they are set.