underscoreus Posted July 23, 2020 Share Posted July 23, 2020 (edited) [See bottom post for explanation on how I solved this issue!] Hey guys! I'm having some issues in connecting a piece of vellum cloth that has vellum strut constraints inside of it at the end of a vellum hair constraint. The idea is to simulate a piece of debris stuck to the end of a wire dangling around colliding with things. The setup works in the sense that they are connected and moving together, however my issue is that the piece of cloth seems to be given unlimited spin as soon as the constraints holding the strutted cloth piece to the deforming geo of my RBD sim are removed. It keeps spinning out of control and I have run out of ideas on what might be causing it or how to mitigate it. So far I've tried: Progressively upping the constraint iterations as well as the substeps (I am now at 10 substeps and 1500 constraint iterations) Pop drag Pop spin drag Custom vex drag on v as well as w and Pop speed limit As far as I can tell by looking at the orient attribute visualized the hair geometry (after sim) remains fairly calm and stable and the cloth is what is introducing all the motion. The best results I saw were using the pop speed limit with very high numbers and even then the best it could manage was to make the behavior happen in slow motion instead of actually stopping it. Has anyone of you had any kind of experience like this? If so I would love to hear about it, especially if you managed to solve it! I've added a short video file of a flipbook showing the issue. I have also added my hipfile as well as the caches needed to run it, I tried to go over all of the file nodes to re-path the caches but there might be some that I missed I realize now. Here is the link to the RBD sim cache I use as a collision if you want to try the full sim (note that the cache is around 5 GB): https://drive.google.com/drive/folders/1bjnrcHzUBgRdpwfgxu97RZ7m7SeBOsQx?usp=sharing Thanks for the read! Stay safe out there! Vellum_Hair_and_Cloth_Issue.zip 2020-07-21_19-35-16.mp4 Edited August 3, 2020 by underscoreus quick edit Quote Link to comment Share on other sites More sharing options...
Noobini Posted July 23, 2020 Share Posted July 23, 2020 might give 5Gb a miss, i'll throw a Hail Mary: in vellumhair try disabling Compute Missing Orientation, does that do anything ? 1 Quote Link to comment Share on other sites More sharing options...
underscoreus Posted July 23, 2020 Author Share Posted July 23, 2020 (edited) 10 hours ago, Noobini said: might give 5Gb a miss, i'll throw a Hail Mary: in vellumhair try disabling Compute Missing Orientation, does that do anything ? Thanks for the tip! (and sorry for the late reply) Unfortunately it did not seem to change anything disabling the "compute missing orient" for the hair constrained to the cloth. Its still spinning out of control. The source of the spin does seem to be the cloth itself, for some reason it get really strong v after the constraints constraining it too my RBD sim let go. Thanks again though! Edited July 23, 2020 by underscoreus Quote Link to comment Share on other sites More sharing options...
Noobini Posted July 23, 2020 Share Posted July 23, 2020 another idea...what about use string instead of hair ? 1 Quote Link to comment Share on other sites More sharing options...
underscoreus Posted July 23, 2020 Author Share Posted July 23, 2020 (edited) 17 minutes ago, Noobini said: another idea...what about use string instead of hair ? Hmm, maybe. I am using hair because it can compute orientation though. I am planning on having some geometry attached to the end and just using the strutted cloth as a holdout in the vellum sim so collisions and wire behavior are correct. Sorry for just shooting down your suggestions one after another Edited July 23, 2020 by underscoreus Quote Link to comment Share on other sites More sharing options...
underscoreus Posted August 3, 2020 Author Share Posted August 3, 2020 Sorry for bringing back this older thread, I just wanted to add a short addendum on how I was able to solve this issue in case others find them self in this pickle later on. So after some detective work, I found that the freakouts were caused by some constraints I had, attaching my vellum piece to a piece of deforming geometry (vellum attach to geometry constraint). If these constraints were not present the sim ran just fine. My substitute for these constraints were to simply animate my bottom piece to follow my deforming geometry using a point deform before configuring any of the vellum stuff and then when setting up vellum simply checking the "match animation" checkbox and setting the pin type to stopped. Then inside the vellum solver, using a pop wrangle to change the stopped attribute to 0 at a given frame to allow the sim to take over. One thing to be careful off when using this approach is that vellum creates an attribute called "fallback". I don't know what governs when it triggers and when it does not, but when it does, the sim will try to move your geometry back to the position described in the baseP attribute. For some reason it was triggering whenever my piece would hit the ground and the sim would try to send the piece back to the "rest" position. I simply solved this by adding another wrangle in the solver always setting "fallback" to 0 and it seems to have worked. Thanks for all the helpful advice given in this thread! Quote Link to comment Share on other sites More sharing options...
Noobini Posted August 3, 2020 Share Posted August 3, 2020 On 7/24/2020 at 7:16 AM, underscoreus said: Hmm, maybe. I am using hair because it can compute orientation though. I am planning on having some geometry attached to the end and just using the strutted cloth as a holdout in the vellum sim so collisions and wire behavior are correct. Sorry for just shooting down your suggestions one after another no probs at all, if i throw enough darts...one might stick eventually. 1 Quote Link to comment Share on other sites More sharing options...
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