Mokiki Posted February 7, 2017 Share Posted February 7, 2017 (edited) I am new to Houdini so I apologize if this is common knowledge. I tried the search function but haven't found what I was looking for. Currently I am trying to point my gravity towards the surface normals of my collision geometry. The simplest example would be having a tiny planet where your objects(Spheres) are affected by wind; bounces etc. but are not supposed to completely fly off the planet, more like roll along the surface. Hope I didn't make it sound too confusing. It would be great if somebody could point me in the right direction. Big thanks in advance. Edited February 7, 2017 by Mokiki Quote Link to comment Share on other sites More sharing options...
Skybar Posted February 7, 2017 Share Posted February 7, 2017 You could do something like this: forceFromNormals_dv.hip 1 Quote Link to comment Share on other sites More sharing options...
vtrvtr Posted February 7, 2017 Share Posted February 7, 2017 You can also use the pop attract dop. The sop setup is pretty much the same as above https://i.imgur.com/2uM2AhZ.gifv 1 Quote Link to comment Share on other sites More sharing options...
Mokiki Posted February 7, 2017 Author Share Posted February 7, 2017 Thank you David and Vitor for the tips! Really appreciate it. I took a look at your file David and this is pretty much what I tried to achieve. But I still ran into 1 issue that I don't really understand. When trying to rebuild your setup manually I run don't get any simulation going. My rigid body doesn't want to move at all. When I copy your dopnet into my scene the simulation works. I went through each node and checked for differences in the various tabs but I didn't find anything. If you could take a quick look at the attached scene that would be great. (I already know that it is going be something completely obvious ) Oh there was another thing I got curious about. When switching rbdpackedobject for rdbobject and not creating packed geometry in your setup, it doesn't seem to work anymore. Is there any specific reason for this? gravitational_pull_upload.hipnc Quote Link to comment Share on other sites More sharing options...
Sepu Posted February 7, 2017 Share Posted February 7, 2017 (edited) isnt working because you haven't copy the network of the geometry Vop inside the Dop network. About rbd Pack geo http://www.sidefx.com/docs/houdini/nodes/dop/rbdpackedobject Edited February 7, 2017 by Sepu Quote Link to comment Share on other sites More sharing options...
Mokiki Posted February 7, 2017 Author Share Posted February 7, 2017 I will now lower my head in shame from here on onward. No idea why I didn't dive inside the geometry vop. Thank you Sepu for pointing it out. Quote Link to comment Share on other sites More sharing options...
Skybar Posted February 7, 2017 Share Posted February 7, 2017 No shame in being new, asking questions and learning. Can't look at your scene but I guess it's sorted. The nice thing about using packed primitives is that you can control them much in the same way as particles. Quote Link to comment Share on other sites More sharing options...
Mokiki Posted February 7, 2017 Author Share Posted February 7, 2017 Yep it's sorted out everything is working now. I just was curious about why non packed geometry doesn't work in your example. So packed geo allows you to use pop forces in rigid body sims and non packed geo does not. Is that correct? Only reason I bring this up is because I was doing an effect with the ripple solver + custom geometry reacting to an rbd sim and in turn having the rbd sim react to the ripples created. Almost giving it this softbody like look in a way and at some point I noticed I didn't get the back and forth reaction to work until I used non packed geo. I think the error is in my point vop setup. It has trouble reading the point data from the surfaces of the packed objects to drive the deformation for the ripple solver. My goal was to combine that effect with the one mentioned in this thread. Will definitely have to study the help file some more. Nonetheless really appreciate the help. Quote Link to comment Share on other sites More sharing options...
Skybar Posted February 8, 2017 Share Posted February 8, 2017 Yes in that case, where you need to deform the geometry, packed primitives might not be the best choice. They work like a zipfile, you can't access or change whats inside, you can only move it around. You would have to pack it up, do your deformation, and then pack it down again. I haven't used "normal" RBDs in forever so I'm not sure what forces work, but I suppose it's not impossible to do the roughly the same thing but apply the force differently. Quote Link to comment Share on other sites More sharing options...
Noobini Posted February 8, 2017 Share Posted February 8, 2017 noob alert (that's me)...but it's not a question of forces...isn't it because of this....(from help link above): ... This object representation is currently only understood by the Bullet Solver. this is what i found out while doing the rings on the shower curtain thread...so when changed the solver from Bullet to RBD, i couldn't use packed objects anymore...so i changed it to RBD Pointobject... Quote Link to comment Share on other sites More sharing options...
Mokiki Posted February 8, 2017 Author Share Posted February 8, 2017 (edited) I managed to get around the the issue at least in my case by simply importing my rbd objects via dop import and just copying my my initial geo on their position and using that in the point vop driving the ripple solver. It's probably not the most elegant solution but it does it's job for now. Edited February 8, 2017 by Mokiki Quote Link to comment Share on other sites More sharing options...
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