Airship Posted July 8, 2011 Share Posted July 8, 2011 Hey all - Firstly, forgive my abundant naivety regarding Houdini which I've begun working with only recently. I have a question regarding the Debris shelf tool and using it with RB make-breakable objects. I have a sim of my building imploding and I'm rather happy with the motion. I also figured out (with help from other odforce forum topics) how to get the debris particles to spawn from the fractured bits (faces) on the dynamically fractured objects. What I would like to do is cull out the smallest 70% of fractured bits so that the debris spawner is only operating on the "hero" chunks - the biggest 30% or so. This will help cut sim times, etc. down considerably since the number of chunks is quite high. Anyone have any insight? Thanks in advance! Best, Ewan Quote Link to comment Share on other sites More sharing options...
johner Posted July 8, 2011 Share Posted July 8, 2011 What I would like to do is cull out the smallest 70% of fractured bits so that the debris spawner is only operating on the "hero" chunks - the biggest 30% or so. That depends a bit on whether you're doing the debris sim at the same time as the fracture sim or as a post-process. I'd recommend the latter if you can, exactly for reasons like this. Either way you need a way to compute the volume of pieces. This is done for you in DOPs (well the mass is computed, so if you know the density of the objects you know their volume), so you could use a dopoption expression if you still have the sim data. But if you're working with cached geometry, it can be done fairly simply in SOPs as a post-process. Use the Measure SOP to compute volumes for all the primitives that comprise the fractured pieces. Then add a ForEachSop that, for each fractured piece, uses AttributePromote to sum its primitive volumes to get the volume for the overall piece, then AttribPromote that piece volume back to the primitives for the piece. Then you can group or delete any primitives whose volume is below a specified threshold. See attached for an example. delete_by_volume.hip 1 Quote Link to comment Share on other sites More sharing options...
Airship Posted July 8, 2011 Author Share Posted July 8, 2011 (edited) Hey John - Thanks so much for your help. I'm caching the sim and will be handling the debris particle post sim - that's my plan anyway. Your help gives me a clear direction to move in. Digging into your example file now. Thanks much! Cheers, Ewan Added 20 minutes later: Oooooh wow! You pros make it look so easy! Brilliant. That is too cool. Thanks again! Edited July 8, 2011 by Airship Quote Link to comment Share on other sites More sharing options...
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