Naeem Posted April 26, 2012 Share Posted April 26, 2012 (edited) Hi, I am working on a simple FLIP sim. When I simulate with Particle Separation set to 0.1 (11k particles at the start), it caches all 500 frames without any problems. However, when I lower the Particle Separation to anything lower, Houdini gets hung at some point. With Particle Separation set to 0.05 (88k particles), Houdini hung at frame 23 and with 0.02 (1.4m particles) it got hung at frame 19. The scene doesn't really contain anything special, just a few static geos for collision. Any idea what could be causing the issue? P.S. : Forgot to mention this is on a Quad Core machine with 8G of RAM. STORM_GEO_V03_R03.hipnc Edited April 26, 2012 by Naeem Quote Link to comment Share on other sites More sharing options...
pclaes Posted April 26, 2012 Share Posted April 26, 2012 Which build are you using? From the journals: ************************** Tuesday, April 17, 2012 Houdini 12.0.599: Fixed a bug that crashed FLIP sims when the underlying grid exceeded 4 billion voxels. ************************** I think separation and voxelres might be linked with flip, so lowering the separation, will increase you voxel count. That said, 4 billion is a very very high voxel count. Might be something else. Quote Link to comment Share on other sites More sharing options...
Naeem Posted April 26, 2012 Author Share Posted April 26, 2012 Which build are you using? From the journals: ************************** Tuesday, April 17, 2012 Houdini 12.0.599: Fixed a bug that crashed FLIP sims when the underlying grid exceeded 4 billion voxels. ************************** I think separation and voxelres might be linked with flip, so lowering the separation, will increase you voxel count. That said, 4 billion is a very very high voxel count. Might be something else. Hi Peter, I am using 12.0.581. The maximum I tried to go to is 1.4M particles. Also, I didn't change the Grid Scale or the Particle Radius Scale. So, I am not really sure if that's the bug causing the issue. Quote Link to comment Share on other sites More sharing options...
Annon Posted April 27, 2012 Share Posted April 27, 2012 Well it seems pretty consistent with running out of RAM. As you lower the Particle Seperation you're going to get more particles, which is crashing your scene quicker. On the DopNet try setting it's memory limit and outputting an explicit cache Quote Link to comment Share on other sites More sharing options...
Naeem Posted April 27, 2012 Author Share Posted April 27, 2012 Well it seems pretty consistent with running out of RAM. As you lower the Particle Seperation you're going to get more particles, which is crashing your scene quicker. On the DopNet try setting it's memory limit and outputting an explicit cache In my original post I forgot to mention that I am caching to disk and not simulating to RAM. Quote Link to comment Share on other sites More sharing options...
Annon Posted April 27, 2012 Share Posted April 27, 2012 What is your system specs? Quote Link to comment Share on other sites More sharing options...
Naeem Posted April 27, 2012 Author Share Posted April 27, 2012 (edited) What is your system specs? Hi, Please see attached image. Thanks. Naeem. P.S. : Tried using HBATCH and render and the process still got stuck. Edited April 27, 2012 by Naeem Quote Link to comment Share on other sites More sharing options...
Naeem Posted April 28, 2012 Author Share Posted April 28, 2012 One thing that I've noticed is that it always gets stuck while evaluating GAS_Advect; irrespective of the frame. Sometimes on frame 19, 21, 22 or 25. Quote Link to comment Share on other sites More sharing options...
Naeem Posted April 28, 2012 Author Share Posted April 28, 2012 FIXED: For some reason the Wind force was causing a problem. When I tried caching to disk after disabling it, it worked perfectly. Quote Link to comment Share on other sites More sharing options...
johner Posted April 28, 2012 Share Posted April 28, 2012 (edited) FIXED: For some reason the Wind force was causing a problem. When I tried caching to disk after disabling it, it worked perfectly. Most of the DOP forces use a particle's mass to determine acceleration due to the force. Unfortunately with the current FLIP object each particles' mass is a function of the particle radius, so as you decrease particle separation (and radius), you decrease mass, making the same force parameters more powerful. Since you're also adding noise, occasionally you're getting very large velocity spikes, which is making GasAdvect take a long time to solve, since it's limited in the distance it can move a particle per iteration. If you turn on the Performance Monitor you'll also see that GasExternalForces is taking a really long time to solve. So I would look at other options for a wind-type force. Probably the most flexible would be to add noisy velocity directly to the vel field with a GasFieldVOP plugged into the Volume Velocity input on the FLIP Solver. I'd also use the Move Particle Outside particle collision method since you have static geometry, and it will be faster. (Oh, and ideally please post to either odForce or SESI forums, not both. Just about everyone reads both anyway, and that way any responses will be nicely organized in one place for other peoples' future reference.) Edited April 28, 2012 by johner 1 Quote Link to comment Share on other sites More sharing options...
Naeem Posted April 28, 2012 Author Share Posted April 28, 2012 Most of the DOP forces use a particle's mass to determine acceleration due to the force. Unfortunately with the current FLIP object each particles' mass is a function of the particle radius, so as you decrease particle separation (and radius), you decrease mass, making the same force parameters more powerful. Since you're also adding noise, occasionally you're getting very large velocity spikes, which is making GasAdvect take a long time to solve, since it's limited in the distance it can move a particle per iteration. If you turn on the Performance Monitor you'll also see that GasExternalForces is taking a really long time to solve. So I would look at other options for a wind-type force. Probably the most flexible would be to add noisy velocity directly to the vel field with a GasFieldVOP plugged into the Volume Velocity input on the FLIP Solver. I'd also use the Move Particle Outside particle collision method since you have static geometry, and it will be faster. Thanks a lot John! I'll look into it. Quote Link to comment Share on other sites More sharing options...
Naeem Posted April 28, 2012 Author Share Posted April 28, 2012 (Oh, and ideally please post to either odForce or SESI forums, not both. Just about everyone reads both anyway, and that way any responses will be nicely organized in one place for other peoples' future reference.) Sure will do Quote Link to comment Share on other sites More sharing options...
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