VelocityPerpendicular particle orientation doesn't work with 0 speed

System Information:
Intel (R) Core™ i7-6700K CPU @ 4.00GHz, 32 GB, NVIDIA GeForce RTX 2080 SUPER
Reproduction File:
particleorientationbug.rbxl (55.2 KB)

If you create a ParticleEmitter with the Orientation property set to VelocityPerpendicular, setting the speed to 0 will cause nothing to ever render, even with acceleration.

In this picture, there are 3 ParticleEmitters all with VelocityPerpendicular orientation, so the particles should face upwards

The left has only speed, the middle has only upward acceleration, and the right has both. Notice how no particles are visible on the middle emitter.

Expected behavior

When a particle emitter has acceleration but no speed, the particles should still be visible.


You can set the speed to 0.01 as a work around

That’s what I usually do, but it’s important for acceleration to have the same effect since it can be in world space while speed is always relative to the ParticleEmitter’s parent.