Camera-aligned particles stop rendering past a certain amount

[and-rad]

Godot version

v4.0.dev.custom_build [56f73a7]

System information

Windows 10 Pro 21H1, Vulkan, Geforce RTX 2060 (v471.68 studio)

Issue description

3D GPU particles have a Transform Align property that can be used to make particles always face the camera when set to ZBillboard. When this is enabled, particles fail to render once the Amount property is set to something bigger than 7327 (this is the number that I'm getting and it might be platform- or hardware-specific. YMMV).

The same does not happen when the Billboard property on the material that renders the particle geometry is used to create camera-facing particles.

I don't know if this is expected behavior, a known limitation, or an actual bug. But I'm currently working on the 3D particle documentation and if this is in fact not a bug, I would like to include it in the docs somewhere.

Steps to reproduce

• Open the Main scene in the reproduction project
• Notice how the BillboardParams particle node doesn't render any particles while the BillboardMaterial node does
• Open the BillboardParams node in the inspector and change the Amount value in the GPUParticles3D category:
  • anything lower than 7328 and particles are rendered
  • anything greater than 7327 and there are no particles visible from that node
• Do the same for the BillboardMaterial node and observe how particles are rendered fine throughout

Minimal reproduction project

ParticleBillboardConfusion.zip

[clayjohn]

Closing in favour of #67717