Truls Posted November 10, 2010 Share Posted November 10, 2010 Hi guys! I am a bit of a beginner in Houdini, but I have quite a lot of general CG knowledge. What I am going to try doing in Houdini is to make a wooden wall consisting of separate planks (simple tall boxes) that first gets shot up by machine gun fire and then gets really wrecked by artillery shell shrapnel. Could be complex. I am posting here in hope that someone would like to give me a little help and perhaps discuss the concepts with me:) Is it really a good idea to do two consecutive fractures? Perhaps the lines from the first fracture will mess up the second and larger fracture operation? I have started doing a little testing, guided by the new Houdini quickstart tutorial from sidefx. I have run across a problem already. I am able to set up a working fracture sim, but the bullet I am using won't just go through the wall and tear out a little of it, it actually smacks the wall down and bounces back from it. I have tried making it go really really fast, be really really small and be really really heavy, but it just puts more force on the wall. Is it actually possible to simulate a bullet going through a wall and making a hole, or would I have to just smash the wall and then use some other force to get the pieces flying? Also, I found sub-step controls both on object lever and inside the dop network. They aren't linked... How do these play together? Quote Link to comment Share on other sites More sharing options...
johner Posted November 11, 2010 Share Posted November 11, 2010 As you've found, it can be tricky to get objects to fly through a wall with dynamic fracturing. You can do it, but you need to mess with the collision relationships; in your case the bullet should affect the wall but not vice versa. But even if you do that it can be tricky to make sure the wall stays completely still when the bullet passes through. In this case probably better to take a cue from the practical FX guys and place small "charges" (AKA Magnet Forces) everywhere you want a bullet impact to be and have them go off in succession, ending up with a final big blast for the artillery shell. See the attached for an example. I've drawn a curve with points where each impact should be and copied a metaball to each point, then delete all but one of them as the frames progress. These metaballs then serve as the Magnet Forces that make up the charges. You could also do this by avoiding dynamic fracturing completely and pre-fracturing the wall. Then just selectively Activate and blow out pieces around the various bullet spots. Look at the PRE_FRACTURED_WALL node the bullet_blasts geo. There's a lot going on here for an intro to Houdini, but it shows some of the cool procedural nature of it. For example, you can put the Display flag on the PRE_FRACTURED_WALL node, then select the Curve node, hit Enter, and interactively move the bullet holes around. As for the substeps, you can substep the entire DOPNet, or just the RBD Solver. With dynamic fracturing the FractureSolver is a separate solver from the RBD Solver, so you're better off substepping the DOPNet itself, which makes the transitions between intact and fractured objects smoother. Good luck. bullets_wall.hip 2 Quote Link to comment Share on other sites More sharing options...
Truls Posted November 13, 2010 Author Share Posted November 13, 2010 (edited) Hi Johner, Thank you very very much for your thorough answer and for setting up that demo file! I haven't had a chance to check it out before now, but I will be looking at it tonight. I will reply more here when I have checked out the file and gotten a good understanding of what you mean. EDIT: Still haven't gotten really into this - but hopefully will get some more time tomorrow:) I got the pre-fractured wall to respond to my curve edits, which was great! Having some trouble getting the dynamic fracturing to work correctly when I edit the walls size or the curves points, however. Edited November 15, 2010 by Truls Quote Link to comment Share on other sites More sharing options...
kumpa Posted March 2, 2011 Share Posted March 2, 2011 (edited) that is soooo cool Btw, were you responsible for creating dynamic fracturing that is included in h11 or they just took your concept and remade it ? I am really proud of my tiny contribution in form of test object cheers k Edited March 2, 2011 by kumpa Quote Link to comment Share on other sites More sharing options...
johner Posted March 2, 2011 Share Posted March 2, 2011 that is soooo cool Btw, were you responsible for creating dynamic fracturing that is included in h11 or they just took your concept and remade it ? Thanks! Yes, I developed it in collaboration with SESI. There was a lot of stuff to do to get it production-capable. I am really proud of my tiny contribution in form of test object Then you'll be glad to know I used it as a test throughout development Quote Link to comment Share on other sites More sharing options...
kumpa Posted March 5, 2011 Share Posted March 5, 2011 awesome news Big congratulations on fracturing thing, awesome contribution, sesi should include other things like hot and bullet solver in houdini build. Quote Link to comment Share on other sites More sharing options...
Netvudu Posted March 5, 2011 Share Posted March 5, 2011 yeah, the integrated bullet solver screams to be added, even if we can play with third party solutions... Quote Link to comment Share on other sites More sharing options...
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