Various features added for Shell Lit

[jiaozi158]

Edited:

Hi, if you would like to try the changes mentioned below, you can still find it here

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Commit into Shell (Lit) because it is the most performant one among three.

Changes:

1. Add "DepthNormals" Pass (For forward renderer, stores normal only).

• "_CameraNormalsTexture"
  

• Now SSAO (Depth Normal mode) works. (Should enable "After Opaque" in URP 12)

• URP 12 Depth Priming (Depth pre-pass) works.

2. Adding specular scattering. (No effect on front face)

• from "maajor"'s https://github.com/maajor/Marschner-Hair-Unity, licensed under MIT.
  
  

3. Controlling fur length using one texture (Red channel).

• Should be black and white, using red channel if it's color texture.
  

4. Fixed issues when using Depth Priming on URP 12.

• Depth Priming avoids rendering pixels that are occluded by front pixels [probably] which improves performance
  

5. Fixed MainLight Shadow issue on URP 12. (Shell Lit only)

• No shadows #4

6. Add XR single pass instance support for both Shell Lit and Unlit.

• Fixing Lit Geom colors (PP) and shadows, and adding SinglePassInstanced support #8
• Adjusted from cdibbs's PR that:
• avoiding *.cginc files, because URP does not suggest using them.
  

7. Increase maximum Shell Amount (13 to 52). (Optional)

• Using geometry shader instancing, so it requires "#pragma target 4.6". (Equivalent to OpenGL 4.1)

• If the device does not support "#pragma target 4.6", it will fall back to 13 shells maximum. (No error should occur)

• The Shell Step is now being replaced by Total Shell Step.

• so that no matter how many shells are using, fall back fur appearance should not change too much.

• You may control it more from the comments in Shell's "Lit.hlsl".
  
  

• The performance should still be better than the other two method. (Also please try Depth Priming)

• If your fur is "toooo long", you will meet Camera Frustum Culling issue at the edges of view, you can try increasing mesh bounds and that should solve the problem. (Other two fur methods should also meet this issue if "toooo long")

8. Add disable fur shadow option. (Mesh Shadow Only)

• Sometimes, the correct shapes of shadow can be less important (hard to notice? it depends...).
  

Quick tested on Unity 2020.3.23, no visible problem [probably]:

[jiaozi158]

Notes:

The scatter light won't be obvious if smoothness is very low.

Should also disable "Specular Highlights" to avoid flickering.

[jiaozi158]

I am quite confused now.

I heard that negative "light.direction" should be used in shaders, but maajor is using a positive "light.direction". (and looks fine? Did not see upside down lighting in the demo)

• maajor's shader:

• And "light.dir" does not have negative in default:

So positive / negative, which one is correct?
Or I just use positive because it looks OK?

[jiaozi158]

Edited: positive should be correct

Well I think negative direction (green one) is correct. (sadly)

But seems that positive direction can fake the scattering by keeping the "factor" low.

[hecomi]

Thank you for the pull request. I am willing to accept the DepthNormals (I would be happy to receive another pull request!), but I am not willing to accept the other changes. This repository is not a practical library of fur shaders, but rather a sample that comes with the article (https://tips.hecomi.com/entry/2019/10/27/152520) to showcase the implementation, and I want to keep it as simple as possible.

As for the light direction, sorry, I have not read that library so I do not know the detailed implementation. But whether it is positive or negative depends on the internal implementation; I recommend comparing the calculation in the official Unity shader with the Marschner-Hair-Unity calculation (FurBxDF()).

[jiaozi158]

Thank you for the pull request. I am willing to accept the DepthNormals (I would be happy to receive another pull request!), but I am not willing to accept the other changes. This repository is not a practical library of fur shaders, but rather a sample that comes with the article (https://tips.hecomi.com/entry/2019/10/27/152520) to showcase the implementation, and I want to keep it as simple as possible.

As for the light direction, sorry, I have not read that library so I do not know the detailed implementation. But whether it is positive or negative depends on the internal implementation; I recommend comparing the calculation in the official Unity shader with the Marschner-Hair-Unity calculation (FurBxDF()).

Thanks for checking this PR! I will try to make another PR (DepthNormals, Shadow and XR)

Just to confirm, another PR would be something like this or?

• DepthNormals: SSAO, and Depth Priming fix (depth normal mode)
• MainLight shadow fix (from cdibbs's PR)
• XR single pass instance support