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# cars and rotation

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say i have a car. my car has four wheels. say two wheels are on a curb and the other wheels are on the ground. How do I determine the rotation of the car''s body? Any resources for this or anything would be greatly appreciated. thx. andy

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The wheels (or at least wheel arches)* form four points in space defining the orientation of the rigid car body... Join the points and you have a plane, calculating the normal vector of that is trivial since you have 4 simple edges.

The binormal and tangent vectors are two of the outside edges of the plane defined by the four points.

Normalise all the vectors and put them into a matrix - voila the car rotates applicably.

 +---------+ |         |FLW       FRW |         | |         | |         |RLW       RRW |         | +------||-+

An ASCII diagram to show what I''m talking about. FLW is Front Left Wheel, FRW is Front Right Wheel, RLW is Rear Left Wheel, and RRW is Rear Right Wheel. Those are the 4 points in space.

[* Ignoring suspension and tyre pressure, you have four contact points with the surfaces the tyres are on. The basic method can still be used - simply depends on how fudgy/game like this is versus how realistic/simulation like.]

500

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Simon O''Connor
Creative Asylum Ltd
www.creative-asylum.com

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