-- | @addForceAt r f@ increments a 'Body''s force and torque accumulators to have a force @f@ applied at the point @r@ in global coordinates.
addForceAt :: Vec3 Double -> Vec3 Double -> Body -> Body
addForceAt r f b = b {
    bForce = bForce b + f,
    bAngularForce = bAngularForce b + crossp (r - bPosition b) f
    }
addForceAt :: Vec3 Double -> Vec3 Double -> Body -> Body
addForceAt r f b = b {
    bForce = bForce b + f,
    bAngularForce = bAngularForce b + crossp (r - bPosition b) f
    }
addForceAt r f b = b {
    bForce = bForce b + f,
    bAngularForce = bAngularForce b + crossp (r - bPosition b) f
    }