LaGriT (Los Alamos Grid Toolbox) LA-CC-15-069 is a library of user callable tools that provide mesh generation, mesh optimization and dynamic mesh maintenance in two and three dimensions. LaGriT is used for a variety of geology and geophysics modeling applications including porous flow and transport model construction, finite element modeling of stress/strain in crustal fault systems, seismology, discrete fracture networks, asteroids and hydrothermal systems. The general capabilities of LaGriT can also be used outside of earth science applications and applied to nearly any system that requires a grid/mesh and initial and boundary conditions, setting of material properties and other model setup functions. It can also be use as a tool to pre- and post-process and analyze vertex and mesh based data.

Geometric regions for LaGriT are defined as combinations of bounding surfaces, where the surfaces are described analytically or as tessellated surfaces (triangles and/or quadrilaterals). A variety of techniques for distributing points within these geometric regions are provided. Mesh connectivity uses a Delaunay tetrahedralization algorithm that respects material interfaces. The data structures created to implement this algorithm are compact and powerful and expandable to include hybrid meshes (tet, hex, prism, pyramid, quadrilateral, triangle, line) however the main algorithms are for triangle and tetrahedral Delaunay meshes.

Mesh refinement, derefinement and smoothing are available to modify the mesh to provide more resolution in areas of interest. Mesh refinement adds nodes to the mesh based on geometric criteria such as edge length or based on field variable shape. Mesh smoothing moves nodes to adapt the mesh to field variable measures, and, at the same time, maintains quality elements.

LaGriT has three modes of use, 1) command line 2) batch driven via a control file 3) calls from C/Fortran programs. There is no GUI interface.

PyLaGriT is a Python interface that allows LaGriT functionality to be used interactively and in batch mode. It combines the meshing capabilities of LaGriT with the numeric and scientific functionality of Python including the quering of mesh properties, enhanced looping functionality, and user defined error checking. PyLaGriT has been developed to easily generate meshes by extrusion, dimensional reduction, coarsening and refinement of synthetic and realistic data. PyLaGriT enhances the workflow, enabling rapid iterations for use in simulations incorporating uncertainty in system geometry and automatic mesh generation. The PyLagrit Description and Manual are found on github at lanl.github.io/LaGriT/