Václav S(milauer said: (by the date of Sun, 25 Jan 2009 08:40:40 +0100)
> Great to hear that. I hope you will also commit a very simple example, > like 2 of those bumping into each other. when I get it to work - yes. Something like SDECSpherePlane, but with random polyhedrons. > AFAIK the common solution is to cut the shape into parts that are > convex, since convex shapes are mathematically easier to handle. I'm not doing that. In fact it also won't work correctly if two polyhedrons have multiple surfaces of contact.... But I don't care about it now. I used a quite stupid approach of simplifying polyhedron into a list of parallelepipeds made out of each surface-triangle (and a tetrahedron, for more precise collision detection). This allows for quick collision checking - just one dot product and few cross products. See the comments that I have just committed, if you want... > There are sophisticated algorithms for detecting triangular surface > collisions (see httpo://gts.sf.net for some references). For such > complicated shapes, I'm not going this way, it's too complex for me, to understand. And probably slower too. OTOH my solution is not volume-perfect in mathematical sense. > though, what folks in Glasgow do (and what I tried > with tetraheda) is to treat the intersection as volume, i.e. compute > volume and direction in which this volume is the thinnest (that is the > direction of repulsive force); I used exact code for that (which is - > who knows - maybe incorrect: extra/tetra), Bicanic &co in Glasgow get > the direction from some averages over normals of planar elements > involved in the collision. First I'll try a plane directed directly between centers of both polyhedrons in contact. If it gives stupid results, then I'll try least-squares fitting a plane into a cloud of 3D points, using algorithm directly copied from wildmagic library (LGPL). > > And is much slower than spheres, so you can forget about simulations > > with 5000 polyhedrons, anyway. > > > I bet you can forget simulations with 500 polyhedra as well ;-) Do you > have some benchmarks on that, BTW? doesn't work yet. So no benchmarks :) -- Janek Kozicki | _______________________________________________ Mailing list: https://launchpad.net/~yade-dev Post to : [email protected] Unsubscribe : https://launchpad.net/~yade-dev More help : https://help.launchpad.net/ListHelp
