[VFX] Fix new SG integration while using keywords

[PaulDemeulenaere]

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Purpose of this PR

Fix this fogbugz

• Keyword aren't exposed from VFX but we shouldn't fallback to incorrect shader (black in HDRP, compilation error in URP)
• Improve error feedback
• Fix shader generation with VFX & SG + Keyword Permutation

⚠️ This PR doesn't add support of exposed keyword editable in VFX but only prevents compilation issue while using them.

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Testing status

• New GraphicTest (which is actually duplicated between URP & HDRP)
  

• Update image in internal using results from this job and this job Done at https://github.cds.internal.unity3d.com/unity/ScriptableRenderPipelinePrivate/pull/372

• Manual test for error feedback (N.B.: I noticed the refresh of UX was sometime failing, not sure about the repro)

_error_feedback_sg.mp4

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Comments to reviewers

About needed change in ShaderGraph code generation

Without the modification in ShaderSpliceUtil.cs, the generated code ends with:

// Configure the output type-spcific mesh definition and index calculation for the rest of the element data.
#if defined(KEYWORD_PERMUTATION_0) || defined(KEYWORD_PERMUTATION_1) || defined(KEYWORD_PERMUTATION_2)
$include("VFXConfigPlanarPrimitive.template.hlsl")
#endif

The keyword generation is adding the #if condition but the content was already a $include (see here)

See also this conversation about usage of keyword with VFX

About ShaderGraph allowed usage in VFX

The behavior has been fine tuned ⬇️

🔴 : Error
🟠 : Warning
🟢 : Allowed

Before

Type	Not Exposed	Exposed
Virtual Texture	N/A (always exposed)	🔴
Gradient	🔴	N/A (so far, always not exposable)
Diffusion profile	🔴	🔴
Keywords (local/global & multicompile/shaderfeature)	🔴	🔴

In case of error, we were fallbacking to an unexpected shader generation which can lead to a black material in HDRP or compilation error in URP.

After

Type	Not Exposed	Exposed
Virtual Texture	N/A (always exposed)	🔴 Critical issue, we won't compile.
Gradient	🟢	N/A (so far, always not exposable)
Diffusion profile	🟢 (not sure it's recommanded neither)	🔴 Unexpected behavior.
Keywords (local/global & multicompile/shaderfeature)	🟢	🟠 The value isn't visible in VFX Output but the material can be modified by script. It can have an odd behavior due to the default keyword state. However, it should be consistent with general material usage.

In case of error, the output is discared from the compilation. When it's a warning, the generation is proceeding but there is an error feedback in VFX (the Debug.LogWarning is kept since these problems can occurs with ShaderGraph modification)

About error feedback from compilation

We were already following a pattern Begin()/End() with SetupCompilation()/EndCompilation().
I added a way to collect and store errors/warnings during compilation to supply them in GenerateErrors.
It also affects the old shader graph integration when a shader graph Lit is used on Unlit output and vice versa.

Additionnal Note

Known issue about missing inspector UX from material (see 1388531), the problem landed in 2022.2.0a1.9_e743b07bbaa9

[VitaVFX]

Hi! Dropping WIP Test Doc. Jotted down several questions.

[VitaVFX]

Thanks for addressing this!

All raised concerns were fixed, couldn't find any other oustanding behavior specific to VFX. Resharing Test Doc for visibility.

[PaulDemeulenaere]

Moving to internal : https://github.cds.internal.unity3d.com/unity/unity/pull/8564