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POCalculating and applying friction
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copied!<p>I have been researching how to apply friction and there is a part I am stuck on, which is how to apply that friction to the velocityy (if in fact I am calculating the friction force correctly that is).</p> <p>When I have a ball on a surface, with a normal of (0, 1, 0), with a present velocity of (2, 0, 0) then I will calculate my friction force as (0, -0.3, 0). However, what I don't understand is how to properly apply that to my velocity. If I simply, subtract it then my velocity will be (2, -0.3, 0), however, shouldn't the friction be cause the x component to be more less?</p> <p>Here is my current code, if anyone could please take a look at I would greatly appreciate it. There are some optimizations to be made, I am aware of that.</p> <pre><code>mTotalForces = D3DXVECTOR3(0.0f, 0.0f, 0.0f); D3DXVECTOR3 vSurfaceNormalized; D3DXVec3Normalize(&vSurfaceNormalized, &vSurfaceNormal); D3DXVECTOR3 vFrictionForce(0.0f, 0.0f, 0.0f); D3DXVECTOR3 forceAndVelocity = mTotalForces + m_vVelocity; float fVelocityMagnitude = sqrt((forceAndVelocity.x * forceAndVelocity.x) + (forceAndVelocity.y * forceAndVelocity.y) + forceAndVelocity.z * (forceAndVelocity.z)); float fFrictionForceMagnitude = 0.0f; float fFrictionForce = 0.0f; if(fVelocityMagnitude == 0.0f) { fFrictionForce = m_fStaticFrictionCoefficient; D3DXVECTOR3 vStaticFriction = -m_fStaticFrictionCoefficient * vSurfaceNormalized; vFrictionForce = vStaticFriction; } else if(fVelocityMagnitude > 0.0f) { fFrictionForce = m_fKineticFrictionCoefficient; D3DXVECTOR3 vKineticFriction = -m_fKineticFrictionCoefficient * vSurfaceNormalized; vFrictionForce = vKineticFriction; } { float fFrictionForceMagnitude = abs(fFrictionForce * D3DXVec3Dot(&vSurfaceNormalized, &forceAndVelocity)); if(fFrictionForceMagnitude > fVelocityMagnitude) { fFrictionForceMagnitude = 0.0f; m_vVelocity = D3DXVECTOR3(0.0f, 0.0f, 0.0f); } else { m_vVelocity -= vFrictionForce; } } </code></pre> <p>I make the total force zero at the start of this friction function because if there is friction, then the previous force (gravity) should not influence the velocity later. (... right?) </p>

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