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I'm using Box2D.

I think it's something to do with wall's fixture definition, but when a ball goes toward a wall at a 45 degree angle, I would expect it to bounce off at 135 degrees, but it always goes 90 degrees against wall. Why would this be?

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up vote 4 down vote accepted

I was setting a large restitution value (greater than 1), that caused the problem.

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Even if it seems silly, you should mark this the answer to your problem. – William Mariager Jan 16 '12 at 3:44
@MindWorX I understand that but system does not allow me to do it until two days after writing the question. – Tae-Sung Shin Jan 16 '12 at 4:37

I know this is an old question, but I've just come across this solution and found that making sure restitution is not above 1 is not enough. friction also caused differentiation in the angle of which it bounces off. so setting friction to 0 allowed me to bounce a ball up against a 45* wall and get the expected perpendicular reaction.

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