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# Calculate direction vector after collision

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#1
Members - Reputation: **334**

Posted 01 March 2013 - 07:49 PM

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#3
Members - Reputation: **659**

Posted 02 March 2013 - 02:03 AM

For other bodies the force direction depends on the shape and the point of contact.

The velocity of the bodies after collision depends on the masses of the bodies and the restitution, as well as the contact normal. But again, for a perfectly bouncing ball against a wall the solution is easy: reverse the component of velocity along the wall's normal vector.

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#4
Crossbones+ - Reputation: **8694**

Posted 02 March 2013 - 05:07 PM

The velocity of the bodies after collision depends on the masses of the bodies and the restitution, as well as the contact normal. But again, for a perfectly bouncing ball against a wall the solution is easy: reverse the component of velocity along the wall's normal vector.

Gravity still applies while the wall and ball are in contact. This is irrelevant for rigid collisions but becomes important for other types of collisions (notably, soft-body).

The slowsort algorithm is a perfect illustration of the multiply and surrender paradigm, which is perhaps the single most important paradigm in the development of reluctant algorithms. The basic multiply and surrender strategy consists in replacing the problem at hand by two or more subproblems, each slightly simpler than the original, and continue multiplying subproblems and subsubproblems recursively in this fashion as long as possible. At some point the subproblems will all become so simple that their solution can no longer be postponed, and we will have to surrender. Experience shows that, in most cases, by the time this point is reached the total work will be substantially higher than what could have been wasted by a more direct approach.

- *Pessimal Algorithms and Simplexity Analysis*

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#5
Members - Reputation: **659**

Posted 02 March 2013 - 06:51 PM

The velocity of the bodies after collision depends on the masses of the bodies and the restitution, as well as the contact normal. But again, for a perfectly bouncing ball against a wall the solution is easy: reverse the component of velocity along the wall's normal vector.

Gravity still applies while the wall and ball are in contact. This is irrelevant for rigid collisions but becomes important for other types of collisions (notably, soft-body).

Gravity is quite far down the list of effects to consider. Given the nature of the question, I'm sure frictionless rigid bodies is a good starting point.

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#6
Crossbones+ - Reputation: **8694**

Posted 04 March 2013 - 06:01 PM

Gravity is quite far down the list of effects to consider. Given the nature of the question, I'm sure frictionless rigid bodies is a good starting point.

I was just highlighting that other forces don't suddenly stop acting upon collision, and must still be considered (and added to the collision response force properly) if the collision time is nonzero (for rigid bodies, it is zero, which is why I said that this is irrelevant for rigid collisions). So in fact gravity is not even on the list of effects to consider.

The slowsort algorithm is a perfect illustration of the multiply and surrender paradigm, which is perhaps the single most important paradigm in the development of reluctant algorithms. The basic multiply and surrender strategy consists in replacing the problem at hand by two or more subproblems, each slightly simpler than the original, and continue multiplying subproblems and subsubproblems recursively in this fashion as long as possible. At some point the subproblems will all become so simple that their solution can no longer be postponed, and we will have to surrender. Experience shows that, in most cases, by the time this point is reached the total work will be substantially higher than what could have been wasted by a more direct approach.

- *Pessimal Algorithms and Simplexity Analysis*