This paper by Valerio Pascucci describes a simple technique to compute isosurfaces on programmable GPUs. Given the vertices of a tetrahedron a simple vertex program computes the position of the vertices, normal and connectivity of the potential portion of an isosurface contained in the tetrahedron (a marching tet approach). One main advantage of this technique is to offload the CPU of the task of computing the isosurface and more importantly to avoid storing the surface in main memory. Interestingly, one could compile a display list for a tetrahedral mesh and display different isosurfaces by changing an OpenGL parameter and always rendering the same list. The paper presents and comments in detail all the source code of the vertex program. (Isosurface Computation Made Simple: Hardware Acceleration, Adaptive Refinement and Tetrahedral Stripping. V. Pascucci, Proceedings of VisSym 2004)