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3D Meshes, determine if meshes are intersecting?


BramJ

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Hello,

I'm building software to control a machine to align a sensor in a camera.

There needs to be a way to limit the movement of the head to prevent damage to the camera, sensor or the machine. Currently this is done by limiting each axis so that you get a box in which the head can move. But this also limits the movement in areas where the head should be able to move freely (to the left and right of camera for instance). I could offcourse define more boxes but it would be even greater if I could load the complex 3D shapes of the machine, head and camera (didn't try yet, but should be possible from what I read) and display them in a 3D Picture box and then determine if the meshes are intersecting or not.

Does anyone have any idea how I can determine if the meshes are intersecting? Any tips in which direction I need to look?

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It probably depends on how large your meshes are. If they don't have many vertices, the brute force approach is simplest and perhaps fast enough. Something like checking that all your vertices in one object are on the "outside" of the triangles of your second object. There are a few ways to compute that - I think one easy one is to compute the scalar triple product [a . (b x c) or det(a b c)] of the vectors a = v1-p, b=v2-p, c=v3-p between a point p(x,y,z) and the vertices v1, v2, v3 of a triangle - the sign of this product/determinant is positive if [p1, p2, p3] are clockwise, and negative if anticlockwise. That gives some idea which side of the triangle you're on. I imagine you also want to stop before they intersect, not after, so checking the distance to the plane of each triangle is also fairly easy.

Searching for "collision detection algorithm" gives a few possibilities, but most are game related or overly complex.

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