# Particle Flow: Subframe Sampling causes hang/crash

**URL:** <https://forums.chaos.com/t/particle-flow-subframe-sampling-causes-hang-crash/17770>\
**Category:** Issues\
**Created:** [April 16, 2008, 1:41pm UTC](https://forums.chaos.com/t/particle-flow-subframe-sampling-causes-hang-crash/17770 "2008-04-16T13:41:30Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![Tommy\_TGCG](https://avatars.discourse-cdn.com/v4/letter/t/258eb7/32.png) [@Tommy\_TGCG](https://forums.chaos.com/u/Tommy_TGCG)\
**Post date:** [April 16, 2008, 1:41pm UTC](https://forums.chaos.com/t/particle-flow-subframe-sampling-causes-hang-crash/17770/1 "2008-04-16T13:41:30Z")

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Hello!

I have a Pflow setup that Vray ( 1.5 sp1, max x64 9 or 2008 ) does not seem to like:

In the birth event, the “subframe sampling” is on, because the particles are supposed to bounce off a collider object that is very close to the emitter object. If it’s off half of them just go through the collider.

And the bad thing starts now: when the particle amount gets around 10000 (i’m not certain this is the reason though) Vray just hangs at “updating instances” for the Pflow object. Last lines in the vraylog are:

Updating object PF Source 01-\>Event 04  
Number of particles for “PF Source 01-\>Event 04” is 91  
Updating object PF Source 01-\>Event 02  
Number of particles for “PF Source 01-\>Event 02” is 9503  
Updating object PF Source 01-\>Event 01  
Number of particles for “PF Source 01-\>Event 01” is 100

Preparing instances  
Creating render mesh for “Plane01PF”: fixed mesh  
Creating render mesh for “PF Source 01-\>Event 04”: moving mesh  
Creating render mesh for “PF Source 01-\>Event 04”: moving mesh  
(END OF FILE)

3ds Max is “not responding” in task manager, and shows 25% cpu usage (a single cpu core is occupied I guess).

The funny thing is that SOMETIMES is does render. Like 1 out of 10 tries it does go past that stage.

I tried many things, but only when I turn off “subframe sampling” in the birth event the problem is gone.

I’ll probably have to re-render the whole sequence with new settings and tweak the collisions again. Luckily I’m not facing a deadline this time :).

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**Author:** ![vlado](https://avatars.discourse-cdn.com/v4/letter/v/779978/32.png) [@vlado](https://forums.chaos.com/u/vlado)\
**Post date:** [April 16, 2008, 2:40pm UTC](https://forums.chaos.com/t/particle-flow-subframe-sampling-causes-hang-crash/17770/2 "2008-04-16T14:40:00Z")

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This should be corrected for SP2. Apparently PFlow did not like the method V-Ray was using to update the particle system and fell into an infinite loop.

Best regards,  
Vlado

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**Author:** ![Neilg](https://dub1.discourse-cdn.com/chaosprd/user_avatar/forums.chaos.com/neilg/32/7044_2.png) [@Neilg](https://forums.chaos.com/u/Neilg)\
**Post date:** [April 16, 2008, 4:52pm UTC](https://forums.chaos.com/t/particle-flow-subframe-sampling-causes-hang-crash/17770/3 "2008-04-16T16:52:05Z")

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Any ETA on when that will be ready vlado? Theres a good chance I might hit this bug in 3/4 weeks…

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**Author:** ![instinct](https://dub1.discourse-cdn.com/chaosprd/user_avatar/forums.chaos.com/instinct/32/74489_2.png) [@instinct](https://forums.chaos.com/u/instinct)\
**Post date:** [April 16, 2008, 4:57pm UTC](https://forums.chaos.com/t/particle-flow-subframe-sampling-causes-hang-crash/17770/4 "2008-04-16T16:57:06Z")

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according to the frontpage 4 days 😛

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**Author:** ![Tommy\_TGCG](https://avatars.discourse-cdn.com/v4/letter/t/258eb7/32.png) [@Tommy\_TGCG](https://forums.chaos.com/u/Tommy_TGCG)\
**Post date:** [April 21, 2008, 10:31am UTC](https://forums.chaos.com/t/particle-flow-subframe-sampling-causes-hang-crash/17770/5 "2008-04-21T10:31:52Z")

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CONFIRMED! it no longer breaks down with the 1.5 sp2 update. Great!

Thank you Vlado and Chaosgroup!