myke3d Posted November 26, 2015 Share Posted November 26, 2015 Hi, I'm having this issue with FLIP sim... one emitter, one thin collision object... and when the particles stay on top of the object they start to vanish I've enabled particle separation and stick on colision and also tried increasing substeps... The only way to reduce is just increasing the colider thickness... but It doesnt help me if I want for example a spoon, and the fluid to flow from top to bottom... flip_strange_behaviour.hiplc Quote Link to comment Share on other sites More sharing options...
sebkaine Posted November 26, 2015 Share Posted November 26, 2015 It looks that your collider object has no thickness. Thus Houdini can't generate volume collider from an object who don't have inner volume. I have switch from volume to object collision in your collider and it work. if you want a Volume collider you will have to extrude your object. in your collider check your collision object by enabling the display collision object. Cheers E flip_strange_behaviour_2.hiplc Quote Link to comment Share on other sites More sharing options...
myke3d Posted November 26, 2015 Author Share Posted November 26, 2015 It looks that your collider object has no thickness. Thus Houdini can't generate volume collider from an object who don't have inner volume. I have switch from volume to object collision in your collider and it work. if you want a Volume collider you will have to extrude your object. in your collider check your collision object by enabling the display collision object. Cheers E Thank you Emmanuel, is a little bit strange... in your file it lost the extrude parameters... but the node is there. Are you using Houdini 15? Quote Link to comment Share on other sites More sharing options...
sebkaine Posted November 26, 2015 Share Posted November 26, 2015 (edited) No Myke i'm under indie 14. But in fact there is a node name polyextrude1 in your scene but it's a merge node in my scene not a polyextrude. It might be a bug indeed ! But i could be wrong on this one, but for very thin object i prefer to use object surface collision instead of volume collision. Edited November 26, 2015 by sebkaine Quote Link to comment Share on other sites More sharing options...
myke3d Posted November 26, 2015 Author Share Posted November 26, 2015 Yes... it seems to work better for think objects. I have also noticed that decreasing the particle separation they tend to keep even using volume sample. Quote Link to comment Share on other sites More sharing options...
fathom Posted November 26, 2015 Share Posted November 26, 2015 15 has a new polyextrude so that's why it would not show up in 14. regarding poly vs volume collisions, doesn't the flip solver end up creating a collision volume anyway? or is that only used for gas interactions and the poly used for particles? Quote Link to comment Share on other sites More sharing options...
myke3d Posted November 26, 2015 Author Share Posted November 26, 2015 15 has a new polyextrude so that's why it would not show up in 14. regarding poly vs volume collisions, doesn't the flip solver end up creating a collision volume anyway? or is that only used for gas interactions and the poly used for particles? it creates a volume colision and you can increase the divisions but for thin surfaces it fails and creates strange behaviours or particles pass the object. you can also build a sdf using a vdb from poly as I did and use it as volume sample in volume colisions insted of default ray intersect mode But as Emmanuel mentioned surface collisions seems to work much better for thin objects like a glass for example. Quote Link to comment Share on other sites More sharing options...
sebkaine Posted November 26, 2015 Share Posted November 26, 2015 (edited) Problem is that i would not have any theorical explanation to this , so if any expert can confirm that it's the correct workflow for thin object that would be great ? Myke i've heard that this technics of don't using a RBD but only plug an SDF in the volume collision of the FLIP is what real Man must do ... I would be interesting to know how you do it if you have a simple hip that illustrates this ! Cheers E Edited November 26, 2015 by sebkaine Quote Link to comment Share on other sites More sharing options...
myke3d Posted November 26, 2015 Author Share Posted November 26, 2015 Problem is that i would not have any theorical explanation to this , so if any expert can confirm that it's the correct workflow for thin object that would be great ? Myke i've heard that this technics of don't using a RBD but only plug an SDF in the volume collision of the FLIP is what real Man must do ... I would be interesting to know how you do it if you have a simple hip that illustrates this ! Cheers E I'm afraid I did not understand the last question... Quote Link to comment Share on other sites More sharing options...
sebkaine Posted November 26, 2015 Share Posted November 26, 2015 (edited) .you can also build a sdf using a vdb from poly as I did and use it as volume sample in volume colisions insted of default ray intersect mode Well i was thinking that you were refering to the technics that consist to don't use any rigid bodies collider. Your collision are only done by plugin VDB SDF in the volume slot of the FLIP solver ... some Houdini friends has recommended this technics , but i haven't the time to try it yet ! I thought that your post was refering to this tricks ... Sorry about the confusion ! forget my request. Edited November 26, 2015 by sebkaine Quote Link to comment Share on other sites More sharing options...
myke3d Posted November 26, 2015 Author Share Posted November 26, 2015 Lol ok... Anyway... Do you know about any technique to do flip morphing? Quote Link to comment Share on other sites More sharing options...
sebkaine Posted November 26, 2015 Share Posted November 26, 2015 (edited) it depends on what you have to morph , but i would try to avoid as much as i can simulation. do the core morph in modeling / vdb / POP. do as much as you can in modeling / zbrush / blendshape / Volume / POP / deformer. put a nice liquid shader + displacement and then only then use this base to simulate your flips sims. keep in mind that it could be a bad advise ... EDIT: here is an exemple of what i was talking about volume collision flip_strange_behaviour3.hiplc Edited November 27, 2015 by sebkaine Quote Link to comment Share on other sites More sharing options...
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