H2O Posted April 14, 2014 Share Posted April 14, 2014 Hi all, I've got a little issue with a flip sim I made. It's a very simple effect actually but I don't know why.. It doesn't work properly! There is a flip fluid emitter inside a voronoied (and exploded) sphere. And I want the fluid to explode and collide with the sphere; Very simple, isn't it? The other thing is, the sim has to be in slow motion. So I made the sim in 100fps (for now). You can watch the result with the .mov below Really, I don't understand why it doesn't work. There is a weird move when flip collide with the sphere... I assume it's about velocity issue but I can't fix it... Here is the hip file too. Could someone help me about this please? Cheers, filp_test_issue.mov flip_sim_issue.hip Quote Link to comment Share on other sites More sharing options...
Skybar Posted April 14, 2014 Share Posted April 14, 2014 (edited) Try use volume collisions and it will probably work better. Right now you've turned off "Use Volume Based Collision Detection" on your Static Object, that is generally a bad idea for FLIP. Edited April 14, 2014 by Skybar Quote Link to comment Share on other sites More sharing options...
H2O Posted April 14, 2014 Author Share Posted April 14, 2014 Thx Skybar. I'm trying this right now. It takes way longer to simulate because of the volume uniform division. I have to increase it a lot to keep right collisions. That was the reason why I turned it off. I'll be back when simulation is finish. Quote Link to comment Share on other sites More sharing options...
Skybar Posted April 14, 2014 Share Posted April 14, 2014 Create a VDB from your collision geo, then on your Static Object DOP set the Mode to "Volume Sample" and point Proxy Volume to your VDB. This is way faster. Quote Link to comment Share on other sites More sharing options...
H2O Posted April 14, 2014 Author Share Posted April 14, 2014 Thx for the tips! Really helpfull Sadly, it's not the problem here. After few tests, it appears that the problem comes from my velocity set. In the source fluid sop, if I check the "add velocity" (in velocity volumes) and set it (like 10,0,0) , whitout the vopsop before (used to set my custom vel). It works perfectly. But when I want to set my own vel with the vopsop and send it to the source fluid sop, it doesn't work anymore. And when I'm talking about "custom" vel, it's a real simple one... I'm a bit confused.. Any ideas? flip_test_simple_vel.mov flip_test_custom_vel.mov Quote Link to comment Share on other sites More sharing options...
eetu Posted April 15, 2014 Share Posted April 15, 2014 I took a look at the original scene: - the fundamental problem is that your flip resolution is so low. particle separation 0.2 * grid size 2 meant that your flip grid resolution is 0.4 your collision geometry has a thickness of 0.3, so problems are inevitable. Even though the flip particles are collided against the geometry, the collision field for the volumetric simulation looks like the attached image. Visualize by looking at flipfluidobject->Visualization->Collision. Even if the collision volume in your rbd object looked good (it doesn't, see below), it is resampled to the flip simulation grid, and if the simulation grid is too coarse the result will not be nice. - your collider's normals are pointing the wrong way, that messed with the collision volume creation (yes, use volume collision) - your velocity sourcing was turned off in the source volume dop Quote Link to comment Share on other sites More sharing options...
H2O Posted April 15, 2014 Author Share Posted April 15, 2014 Hi eetu, Thx for your very helpfull answer! It works perfectly now. Quote Link to comment Share on other sites More sharing options...
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