## Re: [Algorithms] Box<>Tri(Mesh) contact filtering

 Re: [Algorithms] Box<>Tri(Mesh) contact filtering From: Alen Ladavac - 2004-04-30 17:45:27 ```>I begin to wonder if we should take this conversation off-list as it >doesn't seem to be generating a whole lot of interest. Dunno... I prefer talking about stuff on the list, because it might provoke some nice ideas from other people, e.g. Pierre gave us something very nice to check. ;) > [eliminating edge-based contacts in favor of face-based, if they are coplanar] I believe that it cannot falsely discard info, but it would catch only cases between two coplanar triangles. But the same problem happens on edges between no-coplanar tris - e.g. on hilltops and in valleys on terrain. In these cases, separation normal directed along triangle normal is also dominant. Perhaps it would be good to always discard edge-based contacts in favor of face-based if the two are very close? Btw, this might be a good solution for boxes, but doesn't really fix the same problem that happens with other shapes, e.g. capsule (capped cylinder), or sphere. In case of a sphere rolling over terrain, if amount of penetration is not insignificant, when it reaches an edge, it will generate a very similar spurious contact with the edge, in addition to one with face of the triangle directly below its center. In this case the two contacts are not located near each other, yet the edge contact is completely bogus. Now that I'm thinking about it... I believe I remember someone sometimes said something about using gouraud-style normal interpolation for colliding spheres with a mesh, for smoother transitions. Perhaps Pierre knows something about it - I believe Novodex was mentioned in the context. Now, interpolated normals might help here as well. Even for boxes. You might evaluate the interpolated triangle mesh normal at the contact point, and if it is more than say 45 degrees away from the contact normal, ignore the contact. Or some variation on that. Hm... will rethink this more and let you know what I find in the morning. Alen ```