WebGPURenderer: BatchedMesh in WebGL fallback breaks in Firefox

[verekia]

Description

Nothing is rendered when using BatchedMesh and WebGPURenderer in Firefox 138 (on Mac at least, without WebGPU support flag). The WebGLRenderer version works fine.

Reproduction steps

1. Go to https://threejs.org/examples/webgpu_mesh_batch.html with Firefox
2. Nothing shows up

Code

WebGPURenderer

Live example

https://threejs.org/examples/webgpu_mesh_batch.html

Screenshots

WebGPURenderer (webgpu):

WebGPURenderer (webgl):

WebGLRenderer:

Version

176

Device

Desktop

Browser

Firefox

OS

MacOS

[Mugen87]

There is currently no fallback in place when using BatchedMesh with WebGPURenderer and a WebGL 2 backend. The code assumes WEBGL_multi_draw support.

@RenaudRohlinger WebGLRenderer uses a fallback if the extension is not supported. Could we add something similar to the WebGL 2 backend of WebGPURenderer?

three.js/src/renderers/WebGLRenderer.js

Lines 1225 to 1239 in 2ec52a4

	if ( ! extensions.get( 'WEBGL_multi_draw' ) ) {
	const starts = object._multiDrawStarts;
	const counts = object._multiDrawCounts;
	const drawCount = object._multiDrawCount;
	const bytesPerElement = index ? attributes.get( index ).bytesPerElement : 1;
	const uniforms = properties.get( material ).currentProgram.getUniforms();
	for ( let i = 0; i < drawCount; i ++ ) {
	uniforms.setValue( _gl, '_gl_DrawID', i );
	renderer.render( starts[ i ] / bytesPerElement, counts[ i ] );
	}
	} else {

[RenaudRohlinger]

Yes it's should be pretty straightforward, and also use _gl_DrawID in BatchNode.