cwalrus Posted November 6, 2015 Share Posted November 6, 2015 Hey there- Check out the smoke at the end of this clip https://youtu.be/HAA2OCxmgQE It's as though it suddenly loses all of it's dynamic behavior, except for its dissipation... There are no hidden keyframes there ... What the heck is going on? Is it because the emitter (the tire) has gone so far off the right of the frame...? Speculation welcome. Quote Link to comment Share on other sites More sharing options...
Whatsinaname Posted November 6, 2015 Share Posted November 6, 2015 Have you checked your container boundaries as well as if the Gas resize dynamic (in case you are using it) works corretcly? Quote Link to comment Share on other sites More sharing options...
Atom Posted November 6, 2015 Share Posted November 6, 2015 I think it is an illusion. You have no forward motion so the smoke just sits there. Perhaps add some directional wind after the smoke fills up but before the car leaves. The car should be creating some kind of back draft. Quote Link to comment Share on other sites More sharing options...
cwalrus Posted November 6, 2015 Author Share Posted November 6, 2015 Well, it's definitely not an illusion - I thought that at first, actually, but if you step through it, you can literally see the frame at which the smoke stops moving up. It's as though the bouyancy / velocity suddenly keys to zero on that frame. I did check my resize dynamic nodes - the "clamp to maximum bounds" is not checked. However, I strongly suspect the fact that the emitter travels so far away to the right has something to do with it, since these events coincide. I am starting to suspect it may be a RAM issue because of an error message I saw on a node (late night, can't remember) - something on the lines of "ERror Node can't be calculated due to Ram on machine" or something. Also I re-sim'd it last night, with a slightly larger division size, and it made it about 10 frames further before the smoke freezes. See this: https://youtu.be/nSuv5Wdp0yo Quote Link to comment Share on other sites More sharing options...
loopyllama Posted November 6, 2015 Share Posted November 6, 2015 In your video I see the sim bounds moving the entire time. This means the bounds are probably expanding with your car, far beyond the camera frustum. This adds more and more voxels as time goes on, and uses more and more memory for smoke that you cannot see through the camera. You only need to deal with the smoke that the camera can see. Limit your max bounds to be slightly larger than the camera frustum. Quote Link to comment Share on other sites More sharing options...
cwalrus Posted November 6, 2015 Author Share Posted November 6, 2015 That sounds exactly like the problem Jim- thank you - let me apply that fix.... Quote Link to comment Share on other sites More sharing options...
koen Posted November 6, 2015 Share Posted November 6, 2015 Another thing you can look at is the sourcing of the velocity. It looks like the velocities are all just set to zero at one frame. Not sure what would cause this, but if you are sourcing the velocity with a "copy" mode and your source ends up funny, it might overwrite all the velocities in the sim. Not sure if this is still the case, but for a long time houdini did not have a great way to source velocities out of the box, it really pays off to implement an "over" mode and an "max length" mode and they are not hard to do. Hope that helps koen Quote Link to comment Share on other sites More sharing options...
victo160 Posted July 17, 2016 Share Posted July 17, 2016 Just wondering if there was a solution found for this problem, I have a smoke sim that seems to be doing the exact same thing! Quote Link to comment Share on other sites More sharing options...
cwalrus Posted July 17, 2016 Author Share Posted July 17, 2016 definitely a RAM issue, it turns out. either make your bounds smaller, or lower the sim resolution. (or get more Ram) Quote Link to comment Share on other sites More sharing options...
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