In this paper we describe a simple and efficient ray casting engine that is suitable for the rapid exploration of irregular grids composed of tetrahedra cells, or other cell complexes where cells have been broken up into faces. In our method, in a preprocessing phase, all the cells are broken into their corresponding faces. Visibility determination is performed after all the faces have been transformed into screen space; here we compute for each pixel an ordered list of the stabbing boundary faces. The final phase is the actual ray casting, which is performed independently for each pixel, and is basically a walk in the cell complex inside each component of the stabbing ordered list. For color calculations, a simple analytical lighting model is applied to each intersection of ray and cell. Our algorithm is simple, and our implementation fast and robust.