International Journal of Production Research, Vol. 45, No. 2, 15 January 2007, 287–307 Object shape reconstruction through NURBS surface interpolation PRALAY PAL*y and R. BALLAVz yTata Technologies, MSD, Tata Motors Premises, Jharkhand District, Jamshedpur, 831010 India zDepartment of Production Engineering & Management, National Institute of Technology, Jharkhand District, Jamshedpur, 831014 India (Revision received March 2006) The skinning of point cloud models has become one of the most popular reverse- engineering exercises for rapid product development in most manufacturing sectors. Common methods such as ‘polygon generation and segmentation’ and ‘direct surface fitting on segmented data’ exhibit shape loss, distortion, continuity problems and a large number of orphan surface patches. The current work discusses data processing through ‘data rarefaction’ to optimize a data set for true object shape and NURBS-based surface interpolation on rarefied data for a reconstruction with good accuracy. For originally rarefied data, on the other hand, conventional subdivision techniques are applied to construct logical points before surface fitting. NURBS interpolation technology ensures accurate surfaces within a limited computation of knot vectors, weight vectors, bi-directional control net and IGES interface file writing. A few reconstruction examples with their results are shown with computation issues and analysis. Keywords: Point cloud data; Matrix inversion; Rarefaction; IGES; Subdivision 1. Introduction Cost competitiveness, a stricter adherence to quality standards and a shorter time to market are conventionally three of the most important factors for the success of a manufacturing organization. However, innovation, perhaps, has become the most influencing factor for the success of leadership companies round the world. The high- end hardware and software systems available today in the field of engineering design and manufacture have made cycle time reduction a certainty and innovation a reality. Complex products are quickly introduced to the market through design and manufacturing cycles each time with an innovative value addition. Reverse engineering has proved to be a workhorse concept that has made innovations possible with every product launch. ‘Reverse engineering’ includes digital recon- struction and surface modelling using discrete-point data sets that facilitates rapid *Corresponding author. Email: pralaypal@tatamotors.com International Journal of Production Research ISSN 0020–7543 print/ISSN 1366–588X online ß 2007 Taylor & Francis http://www.tandf.co.uk/journals DOI: 10.1080/00207540600688481