Mapping gray-scale image to 3D surface scanning data by ray tracing

摘要

Abstract: The extraction and location of feature points fromrange imaging is an important but difficult task inmachine vision based measurement systems. There existsome feature points which are not able to be detectedfrom pure geometric characteristics, particularly inthose measurement tasks related to the human body. TheLoughborough Anthropometric Shadow Scanner (LASS) is awhole body surface scanner based on structured lighttechnique. Certain applications of LASS requireaccurate location of anthropometric landmarks from thescanned data. This is sometimes impossible fromexisting raw data because some landmarks do not appearin the scanned data. Identification of these landmarkshas to resort to surface texture of the scanned object.Modifications to LASS were made to allow gray-scaleimages to be captured before or after the object wasscanned. Two-dimensional gray-scale image must bemapped to the scanned data to acquire the 3Dcoordinates of a landmark. The method to map 2D imagesto the scanned data is based on the colinearityconditions and ray-tracing method. If the camera centerand image coordinates are known, the correspondingobject point must lie on a ray starting from the cameracenter and connecting to the image coordinate. Byintersecting the ray with the scanned surface of theobject, the 3D coordinates of a point can be solved.Experimentation has demonstrated the feasibility of themethod. !12