Atom Posted March 30, 2021 Share Posted March 30, 2021 (edited) I have a working viscosity simulation. When I replace the tube with a hollow cube, all fluid motion stops on contact with the collision surface? I have set friction to zero, but that does not seem to be the issue. The collision object looks valid. Does anyone know how to make FLIP work in this case? I expected the fluid to continue to ooze out and around the collision object. How are we supposed to make our Cadbury egg simulation? ap_flip_viscosity_by_attribute_inside.hiplc Edited March 31, 2021 by Atom Quote Link to comment Share on other sites More sharing options...
ryew Posted March 30, 2021 Share Posted March 30, 2021 Enabling flipsolver1->Viscosity->Slip on Collision and playing with the Slip Scale attribute seems to help a bit, but I agree that is very odd to see this happening for a fairly straightforward simulation case. It's almost like the viscosity is getting scaled at a rapid rate despite there being nothing set up to do so in the rig. It's worth posting this on the SESI forums and/or sending to their techs for closer inspection if you haven't already, something does seem fishy about that behavior. 1 Quote Link to comment Share on other sites More sharing options...
Vinz Posted March 30, 2021 Share Posted March 30, 2021 I turned on 'slip on collision' (flipsolver/volume motion/viscosity) and turned friction back to 1 ap_flip_viscosity_by_attribute_inside_OD_1.hipnc Quote Link to comment Share on other sites More sharing options...
Vinz Posted March 30, 2021 Share Posted March 30, 2021 sorry, I just realize that this has been already solved Quote Link to comment Share on other sites More sharing options...
Follyx Posted March 31, 2021 Share Posted March 31, 2021 (edited) added a f@viscosity = chf("viscosity"); into your obj/geoemitter/attribwrangle_rnd_viscosity. Depending on your needs adjust the viscosity. flip_viscosity_by_attribute_inside.hiplc Edited March 31, 2021 by Follyx Quote Link to comment Share on other sites More sharing options...
Atom Posted March 31, 2021 Author Share Posted March 31, 2021 Thanks for the replies, everyone. I also received help on Discord which provided the simplest solution. Calculate the collision object using Ray Intersect instead of providing a Volume Sample. For some reason this just fixes it..? 2 Quote Link to comment Share on other sites More sharing options...
ryew Posted March 31, 2021 Share Posted March 31, 2021 (edited) Good to know, thanks for the update. That's a weird as well as non-intuitive fix; I don't know why that would make any difference given that Volume Sample has been reliable every other time I've used it - now it definitely sounds like a bug that SideFX should check into edit: I had to go and tinker some more to try and understand why this behavior is occurring; I've actually found that with a voxel size of 0.025 or above in the Collision Source, it works as expected. Anything below that (even 0.0249999) causes the odd freezing behavior. A relationship between that value and the settings in the simulation is not readily apparent to me, but I feel it is likely there is one. Edited March 31, 2021 by ryew further tinkering 2 Quote Link to comment Share on other sites More sharing options...
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