james_conkle Posted November 5, 2020 Share Posted November 5, 2020 (edited) Hi Everyone, I'm working through Stop Being Afraid of Houdini, by Mograph.com, and in the POPs section I created some particles and would like to contain them inside a sphere. I've made a polygon sphere, extruded it and made it a Static Collider and the particles seem to teleport outside the sphere and collide with the outside of the sphere (I then tried inverting normals but that didn't work). I'm sure it's a simple fix but I'm very new to Houdini and not sure where to go with solving this. Also, what's a good way to either hide or ghost the sphere once inside the DOP network? I've attached my scene here, I apologies it it's not organized correctly. Thank you! POPs_in_sphere-help.hiplc Edited November 6, 2020 by james_conkle Updated title to solved. Quote Link to comment Share on other sites More sharing options...
Vinz Posted November 6, 2020 Share Posted November 6, 2020 Hi James I had a look at your scene. That is right some the particle get ejected outside the sphere instantly.. and the more you res up the collision VDB. the worse it gets.. It is very lucky that I had the same issue once with a flip sim as the answer is the least you expect and is almost impossible to find in books. The container needs to be open somewhere. Apparently particle based simulations don't work in a sealed container. You can cap it but it need to have an opening. So I punched a hole in the sphere and it works fine. Let me know if that works on your end Cheers POPs_in_sphere-help_01.hipnc 1 Quote Link to comment Share on other sites More sharing options...
jkunz07 Posted November 6, 2020 Share Posted November 6, 2020 You can also avoid the polyextrude of the sphere and just enable 'invert sign' on the static object. This tells the solver to treat the interior as hollow an exterior as solid. To hide the sphere or any geometry created by a DOP node, you can click the cyan/eye flag POPs_in_sphere_invert_sign.hiplc 1 Quote Link to comment Share on other sites More sharing options...
james_conkle Posted November 6, 2020 Author Share Posted November 6, 2020 Thank you both! I definitely wouldn't have figured that out and my google fu wasn't turning anything up, but both of those work! Wouldn't have guessed the boolean option, and I knew there was a check box I was missing and totally would've blanked on the Invert Sign - the tool tip talk of laser scanning which I found odd as I have no experience with that. Quote Link to comment Share on other sites More sharing options...
Vinz Posted November 6, 2020 Share Posted November 6, 2020 I must say that the invert sign is a cleaner option as you don't need to render this one and create one with thickness just for render. James, turn off display flag on your collider sphere and create a new geo node for the rendered sphere with thickness.. if yo intend to render.. Quote Link to comment Share on other sites More sharing options...
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