Calculation and visualisation of the thickness of 3D CAD models

We present an algorithm for computing the thickness of a trimmed non-uniform rational B-Spline (NURBS) model, by finding the radius of maximal spheres contained within the modelled object. This information can then be visualised as a colour coded thickness map on the object´s surface, allowing intuitive interpretation by designers and engineers. By making use of surface normal information the task of finding maximal spheres can be reduced to a simple minimisation problem, avoiding the calculation of Delaunay tetrahedra or Voronoi diagrams. Also our method allows the thickness to be evaluated one point at a time, so computation can be focused on a localised region of the model. The simplicity of this method makes implementation straightforward allowing it to be rapidly integrated into existing CAD/CAM packages.