A computer-aided design (CAD) import and tracking system, OiNC, has been developed that is currently being incorporated into the MONK and MCBEND criticality and shielding codes. The system enables analysts to take advantage of the advanced geometry modeling capabilities provided by the solid CAD modelers Autodesk Inventor and Solidworks. Various tracking acceleration techniques are implemented in order to reduce calculation time, including the full or partial automatic conversion of the CAD model to constructive solid geometry (CSG) form. For the criticality benchmark model detailed here, the overall calculation run time for a CAD-based geometry was found to be just 14% longer than an equivalent text-based CSG model. OiNC uses analytical surface descriptions, with full NURBS support, avoiding the approximations and problems associated with meshing. However, meshed models can still be imported and tracked, enabling shielding and criticality calculations to be performed, for example, on impact simulated finite element models.