Contact force vector

[marcimatz]

Hello,

I am trying to obtain the force vector of a contact. In a previous post (http://bulletphysics.org/Bullet/phpBB3/ ... ntact+info), Erwin suggested to use following:

m_appliedImpulse*m_normalWorldOnB/deltaTime

This works fine, but doesn't really represent the full force applied by the contact, since the force will always by perpendicular to one of the surface with above's way of calculating. A contact that has some friction will also generate a non-perpendicular force component that is not taken into account.

Take the example of a cube sitting on the floor. If the floor is horizontal, then above method gives correct result. But if the cube sits on a slightly inclined floor (and the cube is not slipping), then above method will not reflect the force applied by the contact, but only the perpendicular component.

See the attached image for illustration and a comparison with ODE:

contactForces.jpg

My question is: how to retrieve the correct force vector that a contact applies to a rigid body?

Cheers,