TerrainDemo.CDLOD.Node.Select C# (CSharp) Method

        public bool Select(Selection selection, bool parentCompletelyInFrustum, bool ignoreVisibilityCheck)
        {
            BoundingBox boundingBox;
            GetBoundingBox(ref selection.TerrainOffset, selection.PatchScale, selection.HeightScale, out boundingBox);

            ContainmentType containmentType = ContainmentType.Contains;
            if (!parentCompletelyInFrustum)
            {
                selection.Frustum.Contains(ref boundingBox, out containmentType);
            }

            BoundingSphere sphere;
            bool intersected = true;

            if (!ignoreVisibilityCheck)
            {
                selection.GetVisibilitySphere(level, out sphere);
                boundingBox.Intersects(ref sphere, out intersected);
                if (!intersected)
                    return false;
            }

            if (level == 0)
            {
                // we reach a leaf node.
                if (containmentType != ContainmentType.Disjoint)
                    selection.AddSelectedNode(this);
                return true;
            }

            // If this node is out of the next visibility, we do not need to check children.
            selection.GetVisibilitySphere(level - 1, out sphere);
            boundingBox.Intersects(ref sphere, out intersected);
            if (!intersected)
            {
                if (containmentType != ContainmentType.Disjoint)
                    selection.AddSelectedNode(this);
                return true;
            }

            bool weAreCompletelyInFrustum = (containmentType == ContainmentType.Contains);

            // Check a child node's visibility on ahead.
            var someChildrenSelected = false;
            someChildrenSelected |= childTopLeft.PreSelect(selection, weAreCompletelyInFrustum);
            if (childTopRight != null)
                someChildrenSelected |= childTopRight.PreSelect(selection, weAreCompletelyInFrustum);
            if (childBottomLeft != null)
                someChildrenSelected |= childBottomLeft.PreSelect(selection, weAreCompletelyInFrustum);
            if (childBottomRight != null)
                someChildrenSelected |= childBottomRight.PreSelect(selection, weAreCompletelyInFrustum);

            if (someChildrenSelected)
            {
                // Select all children to avoid T-junctions by ignoring a visibiliy range check
                // if can select at least one.
                // The original code tries to select finer nodes as far as possible,
                // and hides parts of a coaser node overlapped by them at render time.
                // But using HW instancing, we must use a same mesh, so can not use such a overlap.
                childTopLeft.Select(selection, weAreCompletelyInFrustum, true);
                if (childTopRight != null)
                    childTopRight.Select(selection, weAreCompletelyInFrustum, true);
                if (childBottomLeft != null)
                    childBottomLeft.Select(selection, weAreCompletelyInFrustum, true);
                if (childBottomRight != null)
                    childBottomRight.Select(selection, weAreCompletelyInFrustum, true);
            }
            else
            {
                if (containmentType != ContainmentType.Disjoint)
                    selection.AddSelectedNode(this);
            }

            return true;
        }