Codes_Shape_from_shading

Matlab codes for ADMM-based variational shape from shading with spherical harmonics lighting

Introduction

These codes can be used to solve the shape-from-shading (SfS) problem (estimate shape, given a single image). Main features:

• possibility to add a shape prior in order to guide the solution (useful for instance in RGB-D sensing)
• minimal surface regularization to smooth out the residual noise
• handles second-order spherical harmonics lighting
• handles orthographic or perspective camera
• handles grey or RGB images

Note: the classic eikonal SfS can also be achieved as a special case.

Demos

The following demo files are provided:

• demo_1_lena_eikonal.m : classic SfS (greylevel image, orthographic camera, frontal lighting) applied to the standard Lena image

• demo_2_vase_SH2.m : refinement of the depth map obtained with a RGB-D sensor. Source of the dataset: https://github.com/pengsongyou/SRmeetsPS

Contents

The main fuctions are in the Toolbox/ folder:

• generic_sfs.m: main SfS code
• theta_fun.m: cost function with respect to the surface gradient values
• estimate_lighting.m: can be used to estimate spherical harmonics lighting, given an image and a shape estimate
• make_gradient.m: finite differences stencils on a non-rectangular grid
• export_obj2.m: to produce a .obj file readable with meshlab

Dependencies

• minFunc: need first be compiled: go to Toolbox/minFunc and run mexAll.m script (source: https://www.cs.ubc.ca/~schmidtm/Software/minFunc.html)

• CMG (recommended for faster results): http://www.cs.cmu.edu/~jkoutis/cmg.html

References

[1] "A Variational Approach to Shape-from-shading Under Natural Illumination", Y. Quéau et al., EMMCVPR 2017