Lighting-up geometry: accurate 3D modelling with a torch and a camera George Vogiatzis, Carlos Hernández, Roberto Cipolla University of Cambridge, Toshiba Research

Our technique Aquire high-res mesh from images taken under changing camera position and illumination Changing illumination uncovers fine geometric detail Assumptions: –Lambertian surface, isolated highlights –Single, distant light-source –Silhouettes of object can be extracted

Image Acquisition Setup

In a nutshell: Estimate light direction in each image With known light directions can estimate surface normals n from pixel intensities i Integrate normals to get geometry n i l

Calibration object –Fully known geometry –Light can be estimated from intensity of all points Light estimation

Visual hull Light estimation

Virtual calibration object –Partially known geometry –Light can be estimated from intensity of correct points

Surface Evolution: Deformable 3D Mesh Evolve mesh until it is predicted appearance under recovered illumination matches images

Results

Advantages –Fully uncalibrated. Camera position and illumination are recovered from images alone –Low cost, practical and efficient alternative to laser range scanning –First image based method to obtain full 3D geometry of untextured objects