FIXED: Listening to mouse has strange effect on particles

This is some odd behavior…

I have a Particle SOP in a Geo, being rendered by a Render TOP which is the background of a Container Panel. Everything is fine, but when I add a mouse position listener to the Container (using a Panel CHOP or a Panel Execute DAT), moving the mouse over the Container speeds up the particle simulation.

When the mouse stops moving, the particles return to normal speed. When moving the mouse continuously, the speedup looks like at least 2X, maybe more.

The network is simple (~5ms cook time) and framerate is always 60.

Particle count is about 120

TD version: 2019.19160

New info on this…

The issue only happens when I have a metaball SOP connected to the Force input of the particles, and the metaball is translated by moving the mouse.

Interestingly, this happens even when the metaball force weight is zero.

Example attached particle test.toe (4.7 KB)

Another update…

This weird particle speedup doesn’t occur when I use The MouseIn CHOP. It’s only when I use the Panel mouse listeners.

It’s as if the panel mouse interrupt causes the particle system to cook extra frames beyond 60 fps.

Hi Todd,

I can replicate this and it’s happening for me only if the viewer of the Particle or Point SOP is turned on. Is that the same for you?
There is a similar behavior in the experimental builds and we have logged the bug.


Hi @Todd_9, this will be fixed in the next experimental we post, build 2019.37100+