BEPUphysics.CollisionTests.CollisionAlgorithms.GJK.GJKToolbox.RayCast C# (CSharp) Method

        public static bool RayCast(Ray ray, ConvexShape shape, ref RigidTransform shapeTransform, float maximumLength,
                                   out RayHit hit)
        {
            //Transform the ray into the object's local space.
            Vector3.Subtract(ref ray.Position, ref shapeTransform.Position, out ray.Position);
            Quaternion conjugate;
            Quaternion.Conjugate(ref shapeTransform.Orientation, out conjugate);
            Vector3.Transform(ref ray.Position, ref conjugate, out ray.Position);
            Vector3.Transform(ref ray.Direction, ref conjugate, out ray.Direction);

            Vector3 extremePointToRayOrigin, extremePoint;
            hit.T = 0;
            hit.Location = ray.Position;
            hit.Normal = Toolbox.ZeroVector;
            Vector3 closestOffset = hit.Location;

            RaySimplex simplex = new RaySimplex();

            float vw, closestPointDotDirection;
            int count = 0;
            //This epsilon has a significant impact on performance and accuracy.  Changing it to use BigEpsilon instead increases speed by around 30-40% usually, but jigging is more evident.
            while (closestOffset.LengthSquared() >= Toolbox.Epsilon * simplex.GetErrorTolerance(ref ray.Position))
            {
                if (++count > MaximumGJKIterations)
                {
                    //It's taken too long to find a hit.  Numerical problems are probable; quit.
                    hit = new RayHit();
                    return false;
                }

                shape.GetLocalExtremePoint(closestOffset, out extremePoint);

                Vector3.Subtract(ref hit.Location, ref extremePoint, out extremePointToRayOrigin);
                Vector3.Dot(ref closestOffset, ref extremePointToRayOrigin, out vw);
                //If the closest offset and the extreme point->ray origin direction point the same way,
                //then we might be able to conservatively advance the point towards the surface.
                if (vw > 0)
                {
                    
                    Vector3.Dot(ref closestOffset, ref ray.Direction, out closestPointDotDirection);
                    if (closestPointDotDirection >= 0)
                    {
                        hit = new RayHit();
                        return false;
                    }
                    hit.T = hit.T - vw / closestPointDotDirection;
                    if (hit.T > maximumLength)
                    {
                        //If we've gone beyond where the ray can reach, there's obviously no hit.
                        hit = new RayHit();
                        return false;
                    }
                    //Shift the ray up.
                    Vector3.Multiply(ref ray.Direction, hit.T, out hit.Location);
                    Vector3.Add(ref hit.Location, ref ray.Position, out hit.Location);
                    hit.Normal = closestOffset;
                }

                RaySimplex shiftedSimplex;
                simplex.AddNewSimplexPoint(ref extremePoint, ref hit.Location, out shiftedSimplex);

                //Compute the offset from the simplex surface to the origin.
                shiftedSimplex.GetPointClosestToOrigin(ref simplex, out closestOffset);

            }
            //Transform the hit data into world space.
            Vector3.Transform(ref hit.Normal, ref shapeTransform.Orientation, out hit.Normal);
            Vector3.Transform(ref hit.Location, ref shapeTransform.Orientation, out hit.Location);
            Vector3.Add(ref hit.Location, ref shapeTransform.Position, out hit.Location);

            return true;
        }

        ///<summary>
        /// Casts a fat (sphere expanded) ray against the shape.  If the raycast appears to be stuck in the shape, the cast will be attempted
        /// with a smaller ray (scaled by the MotionSettings.CoreShapeScaling each time).
        ///</summary>
        ///<param name="ray">Ray to test against the shape.</param>
        ///<param name="radius">Radius of the ray.</param>
        ///<param name="target">Shape to test against.</param>
        ///<param name="shapeTransform">Transform to apply to the shape for the test.</param>
        ///<param name="maximumLength">Maximum length of the ray in units of the ray direction's length.</param>
        ///<param name="hit">Hit data of the sphere cast, if any.</param>
        ///<returns>Whether or not the sphere cast hit the shape.</returns>
        public static bool CCDSphereCast(Ray ray, float radius, ConvexShape target, ref RigidTransform shapeTransform, float maximumLength,
                                         out RayHit hit)
        {
            int iterations = 0;

            while (true)
            {
                if (GJKToolbox.SphereCast(ray, radius, target, ref shapeTransform, maximumLength, out hit) &&
                    hit.T > 0)
                {
                    //The ray cast isn't embedded in the shape, and it's less than maximum length away!
                    return(true);
                }
                if (hit.T > maximumLength || hit.T < 0)
                {
                    return(false); //Failure showed it was too far, or behind.
                }
                radius *= MotionSettings.CoreShapeScaling;
                iterations++;
                if (iterations > 3) //Limit could be configurable.
                {
                    //It's iterated too much, let's just do a last ditch attempt using a raycast and hope that can help.
                    return(GJKToolbox.RayCast(ray, target, ref shapeTransform, maximumLength, out hit) && hit.T > 0);
                }
            }
        }