Assimp.Viewer.AssimpView.HandleMouseInputLocal C# (CSharp) Метод

        private void HandleMouseInputLocal()
	    {
	        Point mousePos;
	        mousePos = Control.MousePosition;
            mousePos = PointToClient(mousePos);

	        g_mousePos.X = mousePos.X;
	        g_mousePos.Y = mousePos.Y;

	        if (g_bMousePressed)
		    {
		        int nXDiff = -(g_mousePos.X - g_LastmousePos.X);
		        int nYDiff = -(g_mousePos.Y - g_LastmousePos.Y);

		        Matrix matWorld;
		        if (g_eClick != EClickPos.Outside)
			    {
			        if( 0 != nYDiff && g_eClick != EClickPos.CircleHor)
				    {
				        Vector3 v = new Vector3(1.0f,0.0f,0.0f);
                        matWorld = Matrix.RotationAxis(v, Geometry.DegreeToRadian((float)nYDiff / 2.0f));
				        g_mWorldRotate = g_mWorldRotate * matWorld;
				    }

			        if( 0 != nXDiff && g_eClick != EClickPos.CircleVert)
				    {
				        Vector3 v = new Vector3(0.0f,1.0f,0.0f);
                        matWorld = Matrix.RotationAxis(v, Geometry.DegreeToRadian((float)nXDiff / 2.0f));
				        g_mWorldRotate = g_mWorldRotate * matWorld;
				    }
			    }
		        else
			    {
			        if(0 != nYDiff || 0 != nXDiff)
				    {
                        var sRect = new Rectangle(Point.Empty, this.Size);

				        // rotate around the z-axis
				        int xPos = g_mousePos.X - sRect.Right/2;
				        int yPos = g_mousePos.Y - sRect.Bottom/2;
				        float fXDist = (float)xPos;
				        float fYDist = (float)yPos / (float)Math.Sqrt(yPos * yPos + xPos * xPos);

				        bool bSign1;
				        if (fXDist < 0.0f)bSign1 = false;
				        else bSign1 = true;
				        float fAngle = (float)Math.Asin(fYDist);

				        xPos = g_LastmousePos.X - sRect.Right/2;
				        yPos = g_LastmousePos.Y - sRect.Bottom/2;

				        fXDist = (float)xPos;
				        fYDist = (float)yPos / (float)Math.Sqrt(yPos * yPos + xPos * xPos);

				        bool bSign2;
				        if (fXDist < 0.0f)bSign2 = false;
				        else bSign2 = true;
                        float fAngle2 = (float)Math.Asin(fYDist);
				        fAngle -= fAngle2;

				        if (bSign1 != bSign2)
					    {
					        g_bInvert = !g_bInvert;
					    }
				        if (g_bInvert)fAngle *= -1.0f;

                        Vector3 v = new Vector3(0.0f, 0.0f, 1.0f);
                        matWorld = Matrix.RotationAxis(v, (float)(fAngle * 1.2));
				        g_mWorldRotate = g_mWorldRotate * matWorld;
				    }
			    }
		    }

	        g_LastmousePos.X = g_mousePos.X;
	        g_LastmousePos.Y = g_mousePos.Y;
	    }