WebGPURenderer: Uniform Group

[sunag]

Related issue: #27101, #26673

GOAL

This PR implements shared and unique Uniform Groups in WebGPURenderer.

NODE UPDATE

Node System has 3 root update systems, FRAME, RENDER, OBJECT.

• FRAME: The Node is updated once per frame.
• RENDER: The Node is updated whenever .render() or .compute() is called.
• OBJECT: The Node is updated in each Mesh or derivative (RenderObject).

Normally, Nodes belonging to projectionMatrix (Camera) and materialColor (Material) are classified as updating type RENDER, and the buffer can be shared with others.

While modelViewMatrix (Mesh), for example, is classified as OBJECT, and is updated every time the object is rendered, its buffer is not shared.

Global nodes like timerGlobal() are classified as FRAME, and are updated once for each requestAnimationFrame(), unlike RENDER it is not updated if there are other RTT in the same frame, the buffer of a FRAME is shared.

UNIFORM GROUP

To implement a uniform group, you just need to tell the uniform which group it will be linked to. Groups will be automatically created in the code, if the group is shared it will look for other equivalent blocks in the active shaders already created to share the buffer. Defining the children of a group should not be a concern for the end user.

import { frameGroup, renderGroup, objectGroup, uniform } from 'three/nodes';

const myUniform = uniform( new THRE.Color( 0x0066FF ) );

// frameGroup, renderGroup, objectGroup are the system groups
myUniform.setGroup( renderGroup );

...
material.colorNode = myUniform;

CUSTOM UNIFORM GROUP

import { uniformGroup, sharedUniformGroup, uniform } from 'three/nodes';

const myUniform = uniform( new THRE.Color( 0x0066FF ) );
const myGroup = sharedUniformGroup( 'myGroup' );

myUniform.setGroup( myGroup );

...
material.colorNode = myUniform;

// For update your group...
// The uniform updates will be sent to the GPU if the version is different from the CPU, 
// in this case use `.needsUpdate=true` to update the version.

myGroup.needsUpdate = true;

NEXT STEP

This PR offers the necessary support for optimization that must be done in separate PRs, so that each Node is in its equivalent group as proposed in the design.

WGSL TEST RESULT

...
// uniforms

struct cameraStruct {
	projectionMatrix : mat4x4<f32>
};
@binding( 0 ) @group( 0 )
var<uniform> camera : cameraStruct;

struct objectStruct {
	modelViewMatrix : mat4x4<f32>
};
@binding( 1 ) @group( 0 )
var<uniform> object : objectStruct;

...
// You need to remove comments left on `CameraNode` to view this example.

[LeviPesin]

Should this be a node, actually? Can't we unify this with the UniformGroup class (and maybe name it NodeUniformGroup)? /ping @sunag

[LeviPesin]

Why we can't just compare groupNode === objectGroup instead of comparing names?

[sunag]

It is possible that more than one sharedUniformGroup node was created with the same name, this would unify them.