Abstract: Ray traversal is the most time consuming part in volume ray casting. In this paper, an acceleration technique for direct volume rendering is introduced, which uses a GPU friendly data structure to reduce traversal time. Empty regions and homogeneous regions in the volume is encoded using extended anisotropic chessboard distance (EACD) transformation. By means of EACD encoding, both the empty spaces and samples belonging to the homogeneous regions are processed efficiently on GPU with minimum branching. In addition to skipping empty spaces, this method reduces the sampling operation inside a homegeneous region using ray integral factorization. The proposed algorithm integrates the optical properties in the homogeneous regions in one step and leaps directly to the next region. We show that our method can work more than 6 times faster than primitive ray caster without any visible loss in image quality.