Creating geometry in Rhino

The first step before you create a mesh is to generate some geometry.

- Open Rhino.
- Set the tolerances for your model (File » Properties » Units)
- Absolute tolerance: the smallest distance in your model. This could be the smallest segment or distance between control points of a curve. Generally 1.e-7. "the absolute tolerance is the maximum permissible distance apart that two objects or elements are permitted to be and still be considered close enough to be touching (hence capable of being joined)" Specific commands that use the absolute tolerance value include: trim, split, intersect, contour, section, project, the rail sweeps, booleans.
- Relative tolerance: the smallest by the largest feature of your model, in percentage. (generally set to 1%)
- Angular tolerance: 3 degrees

- Set the Rhino grid to fit the scale of your model (File » Properties » Grid). If you
- Define the bounding box (if needed)
- Define the structures (fractures, faults, beds) using parametric curves and surfaces (NURBS). All curves and surfaces in Rhino are NURBS.
- If your model has boundaries, then define the boundary surfaces, and put each one of them in a different family.
- Save your file, and close rhino.
- Use the Ansys 3dm2tin.exe converter to turn your geometric data into an Ansys Tetra-readable tetin file.
- Load the tin file (geometry) into Ansys Tetra.

Here is a little cheat-cheat to get you started with Rhino3D rhino3D_cheat_sheet.pdf and a this is the link to a small how-to.