convert_opengl_depth.cl

			float const depthGL = read_imagef (depthImage, depthSampler, (int2) (x, y)).x; // in range [0,1]

			float2 const pixel = (float2) (	(x + 0.5f) / (float) imageSizeX,
											                (y + 0.5f) / (float) imageSizeY); // in range [0,1]

			float4 point_NDC = (float4) (	2.0f * pixel.x - 1.0f, // in range [-1,1]
                                    2.0f * pixel.y - 1.0f, // in range [-1,1]
                                    2.0f * depthGL - 1.0f, // in range [-1,1]
                                    1.0f);

			point_NDC.z -= 1.25e-6f; // apply constant polygon offset for OpenGL depth

			float4 const point_WORLD = matVecMult (trsf_NDC_WORLD, point_NDC);

			float const rayTime = depthGL < 1.f ? length (point_WORLD.xyz / point_WORLD.w - ray.Origin.xyz) : BIGFLOAT;