feat(engine): Transform → BufferTransform + TextureTransform

[donmccurdy]

Work in progress. Adding more functionality required for deckgl aggregation layers.

Changes:

• Renames Transform → BufferTransform
• Adds TextureTransform class

[donmccurdy]

My intentions here are:

• BufferTransform: API-agnostic wrapper around Model which takes Model-like input props, and some additional output-related props, runs the Model, and writes the result of a vertex transformation (via Transform Feedback for now) to a Buffer.
• TextureTransform: API-agnostic wrapper around Model which takes Model-like input props, and some additional output-related props, runs the model, and writes output of the fragment shader to a texture.

In comparison to the current implementation I'm hoping to avoid all of the shader transformation happening in code like transform-shader-utils.ts, with the expectation that callers of the Transform classes do a bit more work to set up a valid Model and shaders. Simple passthrough fragment shaders can still be autogenerated.

I'm hoping this can considerably simplify the code in preparation for API changes in v9.1. I realize there may be some wrinkles in this plan. I did for example see code in deckgl running transform feedback for transitions and also writing output to a 1-pixel fragment shader to detect when a transition has completed. That can probably be handled here but if there are other complicating factors it would be good to know!

I'd also like to try to ensure that the important functionality of the Transform classes is verified directly with unit tests, which will make future changes much easier. This PR contains a simple 'mean' aggregation, which is not working yet. Probably either I'm not drawing pixels to the right coordinates of the framebuffer, or I haven't bound the framebuffer correctly. Currently after transform.run() only the clear color comes back.

[donmccurdy]

To do:

• fix test failures
• add a test with texture as input
• add a test with 'swap' behavior
• clean up TODOs

[donmccurdy]

This should be ready for review. I think the remaining TODOs in code represent open questions, related to my comment above. Thoughts or preferences would be welcome. In the meantime I'll do some tests locally updating deckgl against this PR, to see if I have further opinions on the TODOs.

This is a 'breaking' change to the previous transform API and is, hopefully:

1. sufficient to cover deckgl's current needs
2. easier to understand and update

[donmccurdy]

Current dependencies on/for this PR:

• master
  • PR fix(shadertools): Explicit GLSL version and language #1904
    • PR feat(engine): Transform → BufferTransform + TextureTransform #1896 👈
      • PR Move 'transform-feedback' example out of WIP, fix errors #1883

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