void CollisionSolver::SolveParticleSphereCollision(CollisionMesh& particle,
                                                   const CollisionMesh& sphere)
{
    D3DXVECTOR3 sphereToParticle = particle.GetPosition() - sphere.GetPosition();
    const float lengthSqr = D3DXVec3LengthSq(&sphereToParticle);
    const float combinedRadius = sphere.GetRadius() + particle.GetRadius();

    if (lengthSqr < (combinedRadius*combinedRadius))
    {
        const float length = std::sqrt(lengthSqr);
        sphereToParticle /= length;

        particle.ResolveCollision(sphereToParticle * fabs(combinedRadius-length), 
            sphere.GetVelocity(), sphere.GetShape());
    }
}
void CollisionSolver::SolveParticleHullCollision(CollisionMesh& particle, 
                                                 const CollisionMesh& hull)
{
    // Determine if within a rough radius of the convex hull
    const D3DXVECTOR3 sphereToParticle = particle.GetPosition() - hull.GetPosition();
    const float lengthSqr = D3DXVec3LengthSq(&sphereToParticle);
    const float extendedParticleRadius = particle.GetRadius() * 2.0f;
    const float combinedRadius = hull.GetRadius() + extendedParticleRadius;

    if (lengthSqr < (combinedRadius*combinedRadius))
    {
        Simplex simplex;
        if(AreConvexHullsColliding(particle, hull, simplex))
        {
            simplex.GenerateFaces();
            const D3DXVECTOR3 penetration = GetConvexHullPenetration(particle, hull, simplex);
            particle.ResolveCollision(penetration, hull.GetVelocity(), hull.GetShape());
        }
    }
}