Measuring Shape in the Presence of  Inter-reflections, Sub-surface Scattering and Defocus
Mohit Gupta, Amit Agrawal, Ashok Veeraraghavan & Srinivasa Narasimhan
CVPR 2011

Depth Map (Our Technique)
The goal of this work is to build an end-to-end system for structured light 3D scanning under a broad range of global illumination effects, such as inter-reflections, diffusion and sub-surface scattering. We have designed structured light patterns that are resilient to individual global illumination effects using simple logical operations and tools from combinatorial mathematics. Scenes exhibiting multiple phenomena are handled by combining results from a small ensemble of such patterns. Our methods can be readily incorporated into existing scanning systems without a significant overhead in terms of capture time or hardware.


Mohit Gupta, Amit Agrawal, Ashok Veeraraghavan, Srinivasa G. Narasimhan
IEEE Computer Vision and Pattern Recognition (CVPR) 2011

"Structured Light 3D Scanning in the Presence of Global Illumination"

3D Visualization
Conventional Gray Codes
Modulated Phase Shifting
Previous Techniques

The scene shown above has significant global illumination in the form of interreflections and sub-surface scattering. Conventional Gray codes and phase-shifting result in errors at points receiving inter-reflections. Modulated phase-shifting produces errors on translucent fruits. In contrast, the depth map computed using our techniques is nearly error free. Please see the compilation of results below for more examples.
Presentation with Results
CVPR 2011 Paper

Conventional Gray Codes
(Perform Poorly in Presence of Global Illumination)

Logical XOR-02 Codes
(Good for Handling Inter-reflections)

Logical XOR-04 Codes
(Good for Handling Inter-reflections)

Max Min-Stripe Width
Gray Codes

(Good for Handling Inter-reflections, Subsurface Scattering, Defocus etc)

Novel Patterns proposed in this paper

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Gallery of Results (Click on images for details)
Illustration of our techniques on simple shapes
Scenes with multiple global illumination effects
Translucent objects (sub-surface scattering and diffusion) and defocus
Concave Bowl on Marble Slab
Diffuse V-groove
Metal lamp with strong high-frequency interreflections: Illustration of error correction and detection