CSharpGL.OneIndexRenderer.GetPickedGeometry C# (CSharp) Method

        public override PickedGeometry GetPickedGeometry(RenderEventArgs arg, uint stageVertexId,
            int x, int y)
        {
            uint lastVertexId;
            if (!this.GetLastVertexIdOfPickedGeometry(stageVertexId, out lastVertexId))
            { return null; }

            // 找到 lastIndexId
            RecognizedPrimitiveInfo lastIndexId = this.GetLastIndexIdOfPickedGeometry(
                arg, lastVertexId, x, y);
            if (lastIndexId == null)
            {
                Debug.WriteLine(string.Format(
                    "Got lastVertexId[{0}] but no lastIndexId! Params are [{1}] [{2}] [{3}] [{4}]",
                    lastVertexId, arg, stageVertexId, x, y));
                { return null; }
            }

            PickingGeometryType geometryType = arg.PickingGeometryType;
            DrawMode mode = this.indexBuffer.Mode;
            PickingGeometryType typeOfMode = mode.ToGeometryType();

            if (geometryType == PickingGeometryType.Point)
            {
                // 获取pickedGeometry
                if (typeOfMode == PickingGeometryType.Point)
                { return PickWhateverItIs(arg, stageVertexId, lastIndexId, typeOfMode); }
                else if (typeOfMode == PickingGeometryType.Line)
                {
                    if (this.OnPrimitiveTest(lastVertexId, mode))
                    { return PickPoint(arg, stageVertexId, lastVertexId); }
                    else
                    { return null; }
                }
                else
                {
                    OneIndexPointSearcher searcher = GetPointSearcher(mode);
                    if (searcher != null)// line is from triangle, quad or polygon
                    { return SearchPoint(arg, stageVertexId, x, y, lastVertexId, lastIndexId, searcher); }
                    else
                    { throw new Exception(string.Format("Lack of searcher for [{0}]", mode)); }
                }
            }
            else if (geometryType == PickingGeometryType.Line)
            {
                // 获取pickedGeometry
                if (geometryType == typeOfMode)
                { return PickWhateverItIs(arg, stageVertexId, lastIndexId, typeOfMode); }
                else
                {
                    OneIndexLineSearcher searcher = GetLineSearcher(mode);
                    if (searcher != null)// line is from triangle, quad or polygon
                    { return SearchLine(arg, stageVertexId, x, y, lastVertexId, lastIndexId, searcher); }
                    else if (mode == DrawMode.Points)// want a line when rendering GL_POINTS
                    { return null; }
                    else
                    { throw new Exception(string.Format("Lack of searcher for [{0}]", mode)); }
                }
            }
            else
            {
                if (typeOfMode == geometryType)// I want what it is
                { return PickWhateverItIs(arg, stageVertexId, lastIndexId, typeOfMode); }
                else
                { return null; }
                //{ throw new Exception(string.Format("Lack of searcher for [{0}]", mode)); }
            }
        }