This paper describes a method to generate Delaunay tetrahedral meshes directly from regular volume data by vertex insertion driven by an error criterion. By adapting the mesh to the input data, the method produces meshes suitable for fast and precise volume ray-casting. A partitioning method that splits the mesh into homogeneous sub-meshes is also presented. Such mesh segmentation strategy turns out very useful in applications such as numerical simulation and focus-and-context rendering, where well defined structures are of paramount importance. © 2007 Taylor & Francis Group.