Why do VFX particles change velocity depending on the systems rotation when simulating in world space?

Hello, thank you for checking out my question!

I created a particle system in VFX graph that sends out particles in a straight line. When the emitter moves, I want the particles to continue with their own momentum, which is why i set the simulation to world space (top right corner of any graph block). This works.
As long as the system is rotated 90 degrees in an direction, the stream of particles continues as set up in the node graph. Below you can see the system rotated -90° in the X axis.
193021-screenshot-2022-02-23-192043.png
But when the emitter is rotated 45 degrees in any direction, particle movement directions begin to spread out, specifically in world Y (up/down) direction. It is a smooth transition from the straight line to a cone. Below you can see the system rotated 45° around the X axis.
193022-screenshot-2022-02-23-192103.png

This only happens when the VFX graph is set to world space and the spread along the world Y axis is persistent, no matter around which axis I rotate the system.

If anyone knows a solution to this problem I would be very grateful.

Did you ever solve this issue? I’ve been seeing similar things when rotating along the y-axis as well and not sure how to solve it.

Hi, I experienced the same problem. I figured out the issue was related with the node “Set velocity random per component”. It has a mathematical issue with rotations, however I am not going to explain it here. Here is the solution I found out.

Note: Be sure that Set Velocity module is Local space but the system is world space.