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# Impossible?

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Is there a swept-volume algorithm that deals with moving and rotating 2D lines colliding? Or is this impossible?

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I am not sure but I don''t it is impossible. If you visualize stuff like this you usually can break it down.

Ok rather than dragging it out I will give you my assumption.

- You probably use the velocity and angular velocity on its endpoints to create 2 curves.

- From those curves you fine its closest point to the stationary line.

- From those closest points you find at which instance the line will be at each curve point (you must find the instance in time the line was there during rotation and movement and not make just a line from the 2 points closest points on the curve).

- So now you have 2 new lines made from the moving line. You test those against the stationary line, depending on the earliest instance in time, you have your earliest collision.

- Also for a fail safe you could test 2 overlaps, one at the beginning of movement and one at the end.

Once again this is just an assumption... seems reasonable.

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it must be possible, it''s been done in 3D with triangles. search for Stephane Redon''s thesis. He is doing swept test between meshes under rotation and translation. it involves finding the roots of a quadric equation (I think). basically, if the lines are rotating and translating at constant speed other a time frame (that''s an assumption made by most collision detection algorithms), you can put the motions into an equation, and solve it.

http://www-rocq.inria.fr/~redon/research.htm

http://www-rocq.inria.fr/~redon/papers/eg2002.pdf

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Awesome, thanks guys.

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