private void RenderLine(Vector3 start, Vector3 end, Plane plane, Color color, ICamera camera, I2DRenderer im)
        {
            var line = new Line(start, end);
            var cls  = line.ClassifyAgainstPlane(plane);

            if (cls == PlaneClassification.Back)
            {
                return;
            }
            if (cls == PlaneClassification.Spanning)
            {
                var isect = plane.GetIntersectionPoint(line, true);
                var first = plane.OnPlane(line.Start) > 0 ? line.Start : line.End;
                if (!isect.HasValue)
                {
                    return;
                }
                line = new Line(first, isect.Value);
            }

            var st = camera.WorldToScreen(line.Start);
            var en = camera.WorldToScreen(line.End);

            im.AddLine(st.ToVector2(), en.ToVector2(), color, 2);
        }
        private void AddLine(CircleType type, Vector3 start, Vector3 end, Plane test, CachedLines cache)
        {
            var line = new Line(start, end);
            var cls  = line.ClassifyAgainstPlane(test);

            if (cls == PlaneClassification.Back)
            {
                return;
            }
            if (cls == PlaneClassification.Spanning)
            {
                var isect = test.GetIntersectionPoint(line, true);
                var first = test.OnPlane(line.Start) > 0 ? line.Start : line.End;
                if (isect.HasValue)
                {
                    line = new Line(first, isect.Value);
                }
            }
            cache.Cache[type].Add(new Line(cache.Viewport.Camera.WorldToScreen(line.Start), cache.Viewport.Camera.WorldToScreen(line.End)));
        }