GPUParticles3D not showing in Godot 4
We broke each setting on purpose in a test scene and looked at what was drawn.
Remove a one-shot particle effect when it ends
Connect finished to queue_free, then call restart() after add_child.
Fade out and stop looping particles
Turn off emitting to stop, tween amount_ratio to fade, and free the node after a delay.
Flipbook animation on GPUParticles3D
Particle Billboard, the right frame counts, and an animation speed above 0.
Fire that turns to smoke in a cone
One emitter, no texture files.