GPU Particles 3D dies if their "Scale Curve" stays in zero for too long

[WagnerGFX]

Godot version

v4.1.2.stable; v4.2.beta2

System information

Godot v4.2.beta2 - Windows 10.0.19045 - Vulkan (Forward+, Mobile) - GLES3 (Compatibility) - dedicated NVIDIA GeForce GTX 1650 (NVIDIA; 31.0.15.3742) - Intel(R) Core(TM) i7-2600K CPU @ 3.40GHz (8 Threads)

Issue description

3D particles with a scale curve that stays in zero for a period of time will die silently.

• The period seems to be around 0.05+ of the normalized curve time.
• Those particles disappear and don't emit sub-particles.
• 2D particles don't have the same issue.

The workaround is to use small values, like 0.001, instead of absolute zero.

Steps to reproduce

The reproduction project has a "main_3d" scene that shows the issue, even in the editor.
There is also a "main_2d" scene to show that 2D particles work fine using the same curve.

Minimal reproduction project

GPUParticle3D Scale Curve Zero.zip

[Calinou]

• Related to GPUParticles3D amount parameter emits wrong number of particles when using scale curve #68809.

[WagnerGFX]

Tested in v4.3-stable and v4.4-dev6. The issue is still the same.

[WagnerGFX]

Well well well . . . What do we have here? I think this issue is already fixed. 😆

I decided to test it again with the latest version and all particles are emitting.
Even testing with a constant scale of 0 worked perfectly.

Since it got fixed between 4.4 Stable and 4.4.1 RC1, it might have been solved by the PR linked above.

Is there a reason why the issue was kept open after the PR was merged or can we close it?

[QbieShay]

It fell through when the fix wasmerged, glad it works!