[Shader Graph] Master Stacks [Skip CI]

[elizabeth-legros]

Purpose of this PR

Problem

Currently, the master node definition is too rigid and defined via leaky abstractions. This gives the the following problems:

• Large list of individual master nodes. Changing master node means reconnecting all edges.
• Many HDRP features require HDRP specific master nodes. This prevents the shader from compiling in URP.
• Users cannot define new master nodes without internal Shader Graph access.
• Ports from different stages are mixed into the same master node, this is confusing for users.

There are other problems involved but these are the main concerns because they seriously inhibit our ability to open up our API to customers (internal right now, external later). As Shader Graph adoption grows, this problem continues to get worse.

Solution

We propose a solution where, instead of providing a collection of master nodes, we provide a single, extensible stack. Users will enable and disable shader features, per render pipeline, in the Inspector. These features provide input ports on the stack, where the user then connects graph edges to provide data for those features. Different render pipelines then build a shader using the input data they support, based on the pipeline configuration. This ensures all features are available, but the shader is always in a valid state.

Goals

• All features available from any render pipeline, still compiles on all render pipelines by ignoring unsupported features.
• UX concepts applied meaningfully, and in line with other graph products.
• Extensible design language for future feature work

What do these mean in practice?

• No more master node explosion, all features should be available from one stack
• All HDRP features must be available, and this shader should always have a fallback on URP
• Better parity with VFX and VS, using the same visual language as their stack implementations
• Better visual distinction between vertex and fragment stages.
• Lay the foundations for…
  • Custom interpolators
  • Public “master node API”
  • Layering/custom passes

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TODO

• Fix remaining red tests
• Fix known issues
• Add new tests (edit/graphics)
• Test for performance regressions in graph
• Add changelog entries

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Testing status

PR Template:

• Opened test project + Run graphic tests locally
• Built a player
• Checked new UI names with UX convention
• Tested UI multi-edition + Undo/Redo + Prefab overrides + Alignment in Preset
• C# and shader warnings (supress shader cache to see them)

General Graph usage

• Fill this out...

Upgrade Tests:

• Upgrading V0 > V2
• Upgrading V1 > V2
• All master nodes
  • Various ports connected
  • Various settings enabled
  • Ports that require settings and connected
  • Default port values changed
• PBR specular/metallic (only add one block)
• Alpha clip upgraded from slot logic > bool (PBR/Unlit)
  • Alpha clip value changed
  • Alpha clip connected
• Multiple master nodes
• Master position > Context position
• Sprite masters result in SpriteColor block (legacy)
  • If BaseColor or Alpha are added SpriteColor is ignored
  • SpriteColor cannot be readded
• AxF shaders in URP package
• Upgrading VFX SGs used in VFX graphs

Automated Tests:

• To add. See TODO checklist.

Any test projects to go with this to help reviewers?
Upgrade graphs can be found at https://easyupload.io/rbhlsn (pw: unity)

Test document:
https://docs.google.com/document/d/1O_wnqsQ8zsnsl-QJ83byZJbLk5O8Od740LRASyj_VP0/edit?usp=sharing

Comments to reviewers

[elizabeth-legros]

So with no idea of master nodes now, need to probably put this bool flag on either targets or subtargets

[ghost]

Test document:
https://docs.google.com/document/d/1O_wnqsQ8zsnsl-QJ83byZJbLk5O8Od740LRASyj_VP0/edit?usp=sharing
Please add to PR description

[alelievr]

Sorry, misclick while my PC froze :(

[elizabeth-legros]

Misunderstood when branch off was happening, undoing previous master merge