TetrUSS includes grid generation tools that enable even novice users to construct viscous meshes on complex geometries. Typically, IGES files are used as a starting point, but curves or Plot3D surfaces can be used as well. GridTool is used to patch up the geometry to create a watertight representation, and is also used to place nodal, linear, cylindrical, and spherical sources that dictate grid size, distribution, and stretching.
VGRID takes the patched geometry and sourcing from GridTool, and uses the advancing front and advancing layers methods to create a surface mesh and volume grid. In addition to the GridTool/VGRID approach, unstructured grids for USM3D can be generated with third-party tools such as Pointwise, AFLR3, ICEM CFD, and others.