OnParticleCollide doesn't return Velocity on every bounce. In code it lists all the return pins trigger 'on kill'; however, all other pins return correctly on each bounce but the velocity does not.

I don't believe this is a regression. The licensee reported this was happening in 4.14 but provided their test project in 4.16.

Licensee Description

The issue I am having is that the only collision that produces any velocity value is the collision that is also killed.

For example, if I set a particle to collide three times, the first two collision events show a velocity of 0 and the third will show some correct velocity values. Here's some example debug output:

Particle collision has velocity of X=0.000 Y=0.000 Z=0.000

Particle collision has velocity of X=0.000 Y=0.000 Z=0.000

Particle collision has velocity of X=9.777 Y=50.625 Z=-296.394

Does anybody have any ideas why only one of the collision events produceds a velocity greater than 0?

(Ultimately I am trying to modulate the volume of the particle's sound effect by its velocity).

Steps to Reproduce
  1. Open the attached project
  2. PIE
  3. Watch the print to screen as the particle bounces

Results: The first two bounces, OnParticleCollide returns all zeros. Only on the third bounce that kills the particle will the velocity actually return correctly.

Expected: For the velocity to return correctly with each bounce of a particle.

Have Comments or More Details?

There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-45631 in the post.

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Won't Fix
ComponentUE - Niagara
Affects Versions4.16.14.17
CreatedJun 2, 2017
ResolvedAug 18, 2021
UpdatedSep 19, 2021
View Jira Issue