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Novel Depth Cues from Uncalibrated Near-field Lighting. Sanjeev J. Koppal and Srinivasa Narasimhan. Carnegie Mellon University Sponsors: ONR and NSF. Distant Lighting. Sun. Parallel Rays. Scene. Near-field Lighting. Indoor. Night. Underwater. Underground.
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Novel Depth Cues from Uncalibrated Near-field Lighting Sanjeev J. Koppal and Srinivasa Narasimhan Carnegie Mellon University Sponsors: ONR and NSF
Distant Lighting Sun Parallel Rays Scene
Near-field Lighting Indoor Night Underwater Underground
Calibrated Near Point Light Source 1 2 R Scene Inverse-square fall-off can give depth information (Clark 92, Iwahori et al 94, Kao and Fuh 95, Magda et al 01, Zickler et al 02,Prados and Faugeras 05)
Our Key Idea ‘baseline’ Scene Move an uncalibrated point light source in a line or a plane
Appearance Model BRDF Illumination and Viewing angles Foreshortening Distance to Source
Experimental Setup LED Camera Scene
Light source moves in a line Scene t = 0 t = i Camera t = n
Maxima in Intensity Scene t = 0 t = i Plane perpendicular to light source path. Camera t = n
Lambertian Scenes Lambertian Model: Albedo Solve for maxima location: Quadratic Expression for maxima: Shortest distance to light source path If D is small, maxima happens at t = i
Light source moves in a plane Scene Camera
Integrating the Profile Q Q P P Overlapped Incident Angles Integral of Profile: S < S if: p q Works for convex Lambertian scenes
Matching Profiles Scene Camera
Conclusions • Line or plane paths for a near light source are a ‘baseline’. • Depth cues can be obtained from such uncalibrated light paths. • The cues are from the light source ‘viewpoint’ and not from the camera.