BEPUutilities.Toolbox.GetClosestPointOnTriangleToPoint C# (CSharp) Method

        public static VoronoiRegion GetClosestPointOnTriangleToPoint(ref Vector3 a, ref Vector3 b, ref Vector3 c, ref Vector3 p, out Vector3 closestPoint)
        {
            float v, w;
            Vector3 ab;
            Vector3.Subtract(ref b, ref a, out ab);
            Vector3 ac;
            Vector3.Subtract(ref c, ref a, out ac);
            //Vertex region A?
            Vector3 ap;
            Vector3.Subtract(ref p, ref a, out ap);
            float d1;
            Vector3.Dot(ref ab, ref ap, out d1);
            float d2;
            Vector3.Dot(ref ac, ref ap, out d2);
            if (d1 <= 0 && d2 < 0)
            {
                closestPoint = a;
                return VoronoiRegion.A;
            }
            //Vertex region B?
            Vector3 bp;
            Vector3.Subtract(ref p, ref b, out bp);
            float d3;
            Vector3.Dot(ref ab, ref bp, out d3);
            float d4;
            Vector3.Dot(ref ac, ref bp, out d4);
            if (d3 >= 0 && d4 <= d3)
            {
                closestPoint = b;
                return VoronoiRegion.B;
            }
            //Edge region AB?
            float vc = d1 * d4 - d3 * d2;
            if (vc <= 0 && d1 >= 0 && d3 <= 0)
            {
                v = d1 / (d1 - d3);
                Vector3.Multiply(ref ab, v, out closestPoint);
                Vector3.Add(ref closestPoint, ref a, out closestPoint);
                return VoronoiRegion.AB;
            }
            //Vertex region C?
            Vector3 cp;
            Vector3.Subtract(ref p, ref c, out cp);
            float d5;
            Vector3.Dot(ref ab, ref cp, out d5);
            float d6;
            Vector3.Dot(ref ac, ref cp, out d6);
            if (d6 >= 0 && d5 <= d6)
            {
                closestPoint = c;
                return VoronoiRegion.C;
            }
            //Edge region AC?
            float vb = d5 * d2 - d1 * d6;
            if (vb <= 0 && d2 >= 0 && d6 <= 0)
            {
                w = d2 / (d2 - d6);
                Vector3.Multiply(ref ac, w, out closestPoint);
                Vector3.Add(ref closestPoint, ref a, out closestPoint);
                return VoronoiRegion.AC;
            }
            //Edge region BC?
            float va = d3 * d6 - d5 * d4;
            if (va <= 0 && (d4 - d3) >= 0 && (d5 - d6) >= 0)
            {
                w = (d4 - d3) / ((d4 - d3) + (d5 - d6));
                Vector3.Subtract(ref c, ref b, out closestPoint);
                Vector3.Multiply(ref closestPoint, w, out closestPoint);
                Vector3.Add(ref closestPoint, ref b, out closestPoint);
                return VoronoiRegion.BC;
            }
            //Inside triangle?
            float denom = 1 / (va + vb + vc);
            v = vb * denom;
            w = vc * denom;
            Vector3 abv;
            Vector3.Multiply(ref ab, v, out abv);
            Vector3 acw;
            Vector3.Multiply(ref ac, w, out acw);
            Vector3.Add(ref a, ref abv, out closestPoint);
            Vector3.Add(ref closestPoint, ref acw, out closestPoint);
            return VoronoiRegion.ABC;
        }