ParticleEmitter 'FacingCameraWorldUp' orientation does not face camera correctly

Issue Type: Display
Impact: Moderate
Frequency: Often

Reproduction Steps:
This is the repro place. To make your own, create a ParticleEmitter with Orientation set to ‘FacingCameraWorldUp’. Compare this next to a Beam or Trail with FaceCamera set to ‘true’, and get close to see the difference.
ParticleEmitter inconsistency bug repro place.rbxl (24.0 KB)

Expected Behavior:
This is a front view of a ParticleEmitter emitting square particles with Orientation set to FacingCameraWorldUp (red, on the left), and a Beam with FaceCamera set to true (right side, green).
I would expect these to act pretty much exactly the same as you get closer (the particles should rotate towards the camera, not towards the front direction of the camera).

Actual Behavior:
This is the top-down view of both. The ParticleEmitter remains facing the same direction, while the Beam rotates correctly to face the camera.

Rotating the camera 90 degrees anticlockwise causes this to happen:

Another 90 degrees and it returns to the way it was at first:

This isn’t how this property should work, and this is a big deal for making rain particles look nice. An example of where this is hindering development is shown in this image, where my camera is facing up towards the rain particles coming from above:

There is a pretty obvious line where the particles switch direction from front to behind, instead of wrapping around nicely as they ought to, which would make the effect much smoother with significantly less effort needed.

(also, this feature was added fairly recently, here)


Thanks for the report! We’ve filed a ticket to our internal database and we’ll follow up when we have an update for you.