Lighting-up geometry: accurate 3D modelling with

a torch and a camera

George Vogiatzis, Carlos Hernández, Roberto CipollaUniversity 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: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

il

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

Light estimation

• Visual hull

Light estimation

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

Results

Results

Results

Results

Results

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