Conversion of mesh geometry to watertight boundary representation

A system comprising:

• at least one non-transitory storage medium having instructions of a computer aided design program stored thereon;
• and
• one or more data processing apparatus configured to perform the instructions of the computer aided design program resulting in operations comprising:
• obtaining a first computer model of a three dimensional object, wherein the first computer model comprises a polygon mesh associated with one or more boundary curves;
• producing a quad parameterization computer model of the polygon mesh, wherein the quad parameterization computer model comprises quad parameter domains on the polygon mesh, and wherein at least the quad parameter domains that are adjacent to the one or more boundary curves interpolate the one or more boundary curves;
• and
• forming a second computer model of the three dimensional object, wherein the forming comprises
• constructing one or more locally refinable surface representations from the quad parameterization computer model,
• refining one or more boundaries of the one or more locally refinable surface representations to approximate the one or more boundary curves within a first tolerance value set in accordance with a smallest dimension representable by a geometry modeling kernel used for the second computer model of the three dimensional object,
• freezing control points of the one or more locally refinable surface representations at the one or more boundaries, and
• modifying remaining interior portions of the one or more locally refinable surface representations to approximate the polygon mesh within a second tolerance value that is at least an order of magnitude larger than the first tolerance value.