Xsiv Posted July 8, 2011 Share Posted July 8, 2011 Hi there, I am shattering objects in Houdini and simulating them. All seems to be working fine until I began to add wind/drag/uniform forces into the scene. I really need the object getting crashed into to have some momentum after being hit. Also there are floating pieces as well at the end of the effect. I crank the forces velocity or force to large numbers without any visible effect. Can anyone take a look at this simple scene and tell me why only gravity is working on the RBD objects and not the other forces? Thanks Chris signShatter.hip Quote Link to comment Share on other sites More sharing options...
aghourab Posted July 8, 2011 Share Posted July 8, 2011 (edited) Hi there, I am shattering objects in Houdini and simulating them. All seems to be working fine until I began to add wind/drag/uniform forces into the scene. I really need the object getting crashed into to have some momentum after being hit. Also there are floating pieces as well at the end of the effect. I crank the forces velocity or force to large numbers without any visible effect. Can anyone take a look at this simple scene and tell me why only gravity is working on the RBD objects and not the other forces? Thanks Chris Hey Chris, Your posted scene file needs a external bgeo you haven't posted, nonetheless had a quick look and... Its to do with scene scale/automatic mass calculation. So if you go to your DOP network, and go to the board RBD object, physical tab, and turn off mass. Your objects dissapear on the second frame (cause each object now has a mass of 1kg, and a ludacris amount of force acting on it). If you turn that back on and cranck up velocity in windforce to something as big as your scale force, there is a visible effect. Basically, because youre scene scale is in meters, and your objects are roughly 300m^3 LWH, and mass = density * volume then your average object weight is something like 1000kg/m^3 * 300^m3 = 300000kg. So a little bit of wind force wont affect it. On your Group parameter in uniform force and windforce, you only need to type "piece*" to affect all the pieces of your RBD object, or "*" if you want it to affect all RBD objects. I'd also suggest taking your scene scale down a bit. A billboard is a few meters wide. Keeping a realistic scale will help you avoid problems with simulations. Hope that helps! Edited July 8, 2011 by aghourab Quote Link to comment Share on other sites More sharing options...
Xsiv Posted July 8, 2011 Author Share Posted July 8, 2011 (edited) Thanks Ahmad! bGeo file - doh! that bGeo was only a plane - positional exported from Maya. That totally took care of my problem of forces. Globally. My next thought on this was putting a fan to this "hit" location to get a localized wind force, with attenuation. Thank you. Chris Edited July 8, 2011 by Xsiv Quote Link to comment Share on other sites More sharing options...
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