Reverse engineering is a method of creating a 3D virtual model from an existing physical part for use in 3D computer-aided design (CAD), computer-aided manufacturing (CAM), computer-aided engineering (CAE), or other software. The process involves measuring an object and then reconstructing it as a 3D model.

Reverse engineering is useful to analyze product functionality, analyze subcomponents, estimate costs, and identify potential patent infringement. It may also be used to supply documentation that was either lost or never written, typically for parts designed before CAD software became widespread.

The physical object can be measured using 3D scanning technologies mounted on coordinate measuring machines (CMMs), portable coordinate measuring machines (PCMMs) such as arms, and structured white light digitizers. The measured data, usually represented as a point cloud, lacks topological information and is therefore often processed into a triangular-faced mesh (STL) file and then modeled into a more usable format such as a set of NURBS* surfaces or a solid CAD model.

* Non-uniform rational basis spline (NURBS)