Interactive Hierarchical Space Carving with Projectorbased Calibrations Martin

Interactive Hierarchical Space Carving with Projector-based Calibrations Martin Granger-Piché, Emric Epstein, Pierre Poulin { grangem | epsteine | poulin } @ iro. umontreal. ca Results Interactive System Pipeline normal feedback loop continuous intervention move camera or move object or zoom camera on object silhouette carving on dynamic image list image • acquisition • cleanup • calibration visualization of current 3 D model … system initialization increase subdivision on entire model or selected region Abstract We present an interactive reconstruction system based on space carving. The user controls the camera and object positions and their impact on the reconstruction is immediately displayed. The flow of images is used first for silhouette carving, and then representative images are stored in a hemispherical structure for balanced color carving. Projected color points on the measured background or on the object (acquired by structured light) allow for automatic and adapted calibration of the camera. The octree-based object representation is central to our space carving algorithm: voxels are efficiently carved out at their largest size, images are treated at their appropriate level, and 3 D regions are subdivided only when necessary. occasional intervention threshold modification for color comparison generation of structured light calibration points save current 3 D model Projector-based Calibrations color carving on static and dynamic image structures on user request … static dynamic Octree-based Space Carving Contributions 1. Interactive system • tools to give control to the user • visual feedback loop • real-time simultaneous image acquisition, segmentation, calibration, and reconstruction display 16 x 16 2. Projector-based calibrations 32 x 32 • automatic camera calibration with projected color points • zoomed camera calibration with projected points on the object, which are obtained with structured light • automatic stand tracking 3. Octree-based space carving • compactness : subdivision of only external boundary voxels • efficiency : largest voxels are carved before subdivided • hardware visible voxels detection • appropriate octree level for each image 64 x 64 4. Image processing • RGB ellipsoid : fast and robust color detection • automatic background segmentation All structured light points Selected valid points to allow zoomed in camera calibration 256 x 256 Our Technique Standard Space Carving