BatchedMesh Example much slower on WebGPU than WebGL on Android

[Makio64]

Description

On Android ( Samsung Galaxy S20 FE ) BatchedMesh Example WebGPU is much slower :

WebGPU : ~13FPS
WebGL : ~25FPS

Reproduction steps

1. load on Android https://threejs.org/examples/?q=bat#webgpu_mesh_batch
2. enabled/disable WebGPU

Code

Live example

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Screenshots

No response

Version

r169

Device

Mobile

Browser

Chrome

OS

Android

[RenaudRohlinger]

The multiDrawAPI isn't currently supported in WebGPU, which is why a single multi-draw call with 20,000 batched elements performs significantly better in WebGL, especially on smartphones.

However, there’s good news! A new MultiDrawIndirect API is on the horizon for WebGPU, which is expected to surpass the performance of the WebGL version:
gpuweb/gpuweb#1354 (comment)
https://issues.chromium.org/issues/369246557/dependencies

This API is already available in Chrome Canary behind the chromium-experimental-multi-draw-indirect flag, enabled through enable-unsafe-webgpu. I plan to begin working with it over the coming weeks, as multi-draw is an important part of my workflow.

In the meantime, as discussed in this PR, we can implement a workaround using multiple drawIndirect() calls with a single indirect buffer, mapped at different offsets for each draw alongside Render Bundles. This approach can mimic the upcoming MultiDrawIndirect API until it becomes widely available: #29197 (comment)

For now, I’ll wait for @Spiri0's work on implementing drawIndirect that looks very promising, which will provide a solid base for that work:
#29568 (comment)