Particle Bug when emitting objects #39881

Closed
opened 2014-04-24 18:38:57 +02:00 by Ben Steward · 11 comments

System Information
Windows 7 64bit, Nvidia 660ti

Blender Version
Broken: 2.7
Worked: (optional)

Short description of error
I have group 3 different shaped objects to simulate rock particles in a ground crack simulation. I have then set-up a basic particle system in a basic shape as the emitter. When i first run the animation within blender after setting the particle system, everything works as it should. When it then loops back to the beginning or if i cache the particle system, it all goes slightly weird? the particles seem to float up and down when they have come to rest and do not remain static. I thought this was just an internal glitch and once rendered would resolve, but it doesn't. The glitch does pull through to the render.

It is just a quick 3 sec simulation I'm doing to then work on within a larger animation. I know that there will be better ways of achieving the same effect, however I am pretty new to all this so would greatly appreciate some help. I have attached the blend file and the short rendered clip (both are relatively small files.

Exact steps for others to reproduce the error
alter the particle settings hit play and all will be well, let it run to loop back and check the movement of the resting particles.
TEST_CRACK0001-0075.avi
web_smash2.blend

web_smash2.blend1

**System Information** Windows 7 64bit, Nvidia 660ti **Blender Version** Broken: 2.7 Worked: (optional) **Short description of error** I have group 3 different shaped objects to simulate rock particles in a ground crack simulation. I have then set-up a basic particle system in a basic shape as the emitter. When i first run the animation within blender after setting the particle system, everything works as it should. When it then loops back to the beginning or if i cache the particle system, it all goes slightly weird? the particles seem to float up and down when they have come to rest and do not remain static. I thought this was just an internal glitch and once rendered would resolve, but it doesn't. The glitch does pull through to the render. It is just a quick 3 sec simulation I'm doing to then work on within a larger animation. I know that there will be better ways of achieving the same effect, however I am pretty new to all this so would greatly appreciate some help. I have attached the blend file and the short rendered clip (both are relatively small files. **Exact steps for others to reproduce the error** alter the particle settings hit play and all will be well, let it run to loop back and check the movement of the resting particles. [TEST_CRACK0001-0075.avi](https://archive.blender.org/developer/F85835/TEST_CRACK0001-0075.avi) [web_smash2.blend](https://archive.blender.org/developer/F85836/web_smash2.blend) [web_smash2.blend1](https://archive.blender.org/developer/F85837/web_smash2.blend1)
Author

Changed status to: 'Open'

Changed status to: 'Open'
Ben Steward self-assigned this 2014-04-24 18:38:57 +02:00
Author

Added subscriber: @bena2b

Added subscriber: @bena2b
Ben Steward was unassigned by Bastien Montagne 2014-04-24 21:30:50 +02:00

Added subscriber: @mont29

Added subscriber: @mont29

Changed status from 'Open' to: 'Archived'

Changed status from 'Open' to: 'Archived'
Bastien Montagne self-assigned this 2014-04-25 15:43:22 +02:00

There is no bug here, it’s just that you use the (default) of one chached baked frame each ten, which means the nine in-between are interpolated. Simply set 'Cache Step' setting to one. :)

There is no bug here, it’s just that you use the (default) of one chached baked frame each ten, which means the nine in-between are interpolated. Simply set 'Cache Step' setting to one. :)
Author

Changed status from 'Archived' to: 'Open'

Changed status from 'Archived' to: 'Open'
Author

Hi mont29,

I have changed the cache step to one and the error still occurs???

Hi mont29, I have changed the cache step to one and the error still occurs???
Author

P.S thank you for your help so far,, but I think there is still a little more needed :)

P.S thank you for your help so far,, but I think there is still a little more needed :)
Author

Please see the attached blend files with the cache step set to 1.

play it first time and all seems well, let it loop or cache and then it goes wrong again?

Help!!!

web_smash2.blend

web_smash2.blend1

Please see the attached blend files with the cache step set to 1. play it first time and all seems well, let it loop or cache and then it goes wrong again? Help!!! [web_smash2.blend](https://archive.blender.org/developer/F85895/web_smash2.blend) [web_smash2.blend1](https://archive.blender.org/developer/F85896/web_smash2.blend1)

Changed status from 'Open' to: 'Archived'

Changed status from 'Open' to: 'Archived'

I can’t see any difference between first run (cache building) and later ones here?

As for the “floating” effect, this is because you use a 'Random' value for particle damping of 1! Which means some particles will have (nearly) no damping, and will keep dangling around for ever. Physics simulation are rather tricky to get working OK, since we can’t simulate the real things and have to simplify situations quite a lot, but there is no bug here either.

I can’t see any difference between first run (cache building) and later ones here? As for the “floating” effect, this is because you use a 'Random' value for particle damping of 1! Which means some particles will have (nearly) no damping, and will keep dangling around for ever. Physics simulation are rather tricky to get working OK, since we can’t simulate the real things and have to simplify situations quite a lot, but there is no bug here either.
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Reference: blender/blender#39881
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