Particle positions are not continuous when the Particles node is moved at a high speed (missing interpolation)

[floppyhammer]

Godot version:
3.3rc9, 4.0

OS/device including version:
Windows 10

Issue description:
Particle positions are frame rate dependent, which causes discontinuous distribution of the particles when the particle node moves fast.

Particle2D:

Particle3D:

Steps to reproduce:
Create a 2D or 3D particle node, set a high emission amount, animate the node itself to move fast, observe the particle clusters.

Minimal reproduction project:
No need.

[Calinou]

I don't see a way to solve this, aside of unlocking the framerate by disabling V-Sync. Is there any literature on other engines solving or working around this problem?

Also, particle emission by distance (instead of time) will be supported in 4.0 via manual emission.

[mortarroad]

When emitting, you can simply interpolate between the old and the new transform of the emitter.
This comes with the issue that "teleporting" the emitter doesn't work anymore by just setting the position. (It will cause a thin trail of particles from the old to the new position, because it is considered a very fast movement.)
This could be solved by having a dedicated "teleport" function for that.
And this can also be made into a flag to turn this behavior on and off.

[Calinou]

This could be solved by having a dedicated "teleport" function for that.
And this can also be made into a flag to turn this behavior on and off.

See also godotengine/godot-proposals#671 and godotengine/godot-proposals#1936.

[Calinou]

@floppyhammer In the meantime, you may be able to hide this issue by making particles emitted over a small box area (or perhaps a sphere) rather than a single emission point. When emitted, particles will be evenly spread within the box or sphere. You can do this by changing the emission point property in the particles material. This is available in both Particles and CPUParticles, in both 3D and 2D.

[floppyhammer]

@Calinou Hadn't thought of this workaround. Thanks!

[reduz]

There is a fixed FPS for particles, you can put it to 60 to fix this.

[floppyhammer]

@reduz Setting fixed_fps to 60 has no effect when the game already runs at 60 FPS.

[Calinou]

@reduz Setting fixed_fps to 60 has no effect when the game already runs at 60 FPS.

Do higher fixed_fps values such as 120 look smoother?

[floppyhammer]

@Calinou No, it makes no difference when going beyond 60.

[Calinou]

Closing in favor of godotengine/godot-proposals#8088, as feature proposals are now tracked on the Godot proposals repository.