Reconstruction of Lambertian surfaces by discrete equal height contours and regions propagation (original) (raw)
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Lecture Notes in Computer Science, 2003
This paper describes two new methods for the reconstruction of discrete surfaces from shading images. Both approaches are based on the reconstruction of a discrete surface by mixing photometric and geometric techniques. The processing of photometric informations is based on reflectance maps which are classic tools of shape from shading. The geometric features are extracted from the discrete surface and propagated along the surface. The propagation is based in one case on equal height discrete contour propagation and in the other case on region propagation. Both methods allow photometric stereo. Results of reconstruction from synthetic and real images are presented.
Variable albedo surface reconstruction from stereo and shape from shading
2000
We p r e s e n t a m ultiview method for the computation of object shape and re ectance characteristics based on the integration of shape from shading (SFS) and stereo, for nonconstan talbedo and non-uniformly Lambertian surfaces. First we perform stereo tting on the input stereo pairs or image sequences. When the images are uncalibrated, w e recover the camera parameters using bundle adjustment. Based on the stereo result, we can automatically segment the albedo map (which i s t a k en to be piece-wise constant) using a Minimum Description Length (MDL) based metric, to identify areas suitable for SFS (typically smooth textureless areas) and to deriv e illumination information. The shape and the illumination parameter estimates are re ned using a deformable model SFS algorithm, which i terates bet w een computing shape and illumination parameters. Our method takes into accoun tthe viewing angle dependent foreshortening and specularity e ects, and compensates as much as possible by utilizing information from more than one images. We demonstrate that we can extend the applicability of SFS algorithms to real world situations when some of its traditional assumptions are violated. We demonstrate our method by applying it to face shape reconstruction. Experimental results indicate a signi cant improvement over SFS-only or stereo-only based reconstruction. Model accuracy and detail are improved, especially in areas of low texture detail. Albedo information is retrieved and can be used to accurately re-render the model under di erent illumination conditions.
A New Formulation for Shape from Shading for Non-Lambertian Surfaces
Lambert's model for diffuse reflection is a main assump- tion in most of shape from shading (SFS) literature. Even with this simplified model, the SFS is still a difficult prob- lem. Nevertheless, Lambert's model has been proven to be an inaccurate approximation of the diffuse component of the surface reflectance. In this paper, we propose a new solution of the SFS problem based on a more comprehensive diffuse reflectance model: the Oren and Nayar model. In this work, we slightly modify this more realistic model in order to take into account the attenuation of the illumination due to dis- tance. Using the modified non-Lambertian reflectance, we design a new explicit Partial Differential Equation (PDE) and then solve it using Lax-Friedrichs Sweeping method. Our experiments on synthetic data show that the proposed modeling gives a unique solution without any information about the height at the singular points of the surface. Ad- ditional results for real data are presented t...
Surface shape estimation from photometric images
Optics and Lasers in Engineering, 2004
One of the most studied techniques for recovering surface shapes using a computer vision system is the photometric. This method is based on the analysis of one or several images of an object illuminated from a known direction . This kind of images can be considered reflectance maps that give us information of the surface gradient. In computer vision, the problem of recovering 3D information from shaded images is considered an inverse problem. To integrate surface gradient information it is proposed a regularization technique that gives a stable solution of the inverse problem and allows the possibility of reducing errors caused by noise. Results applied on synthetic and real experimental images are presented. r
Analysis and approximation of some Shape-from-Shading models for non-Lambertian surfaces
The reconstruction of a 3D object or a scene is a classical inverse problem in Computer Vision. In the case of a single image this is called the Shape-from-Shading (SfS) problem and is known to be ill-posed even in a simplified version like the vertical light source case. A huge number of works deals with the orthographic SfS problem based on the Lambertian reflectance model, the most common and simplest model which leads to an eikonal type equation when the light source is on the vertical axis. In this paper we want to overcome this model dealing with non-Lambertian models, more realistic and suitable whenever one has to deal with different kind of surfaces, rough or specular. We will present a unique mathematical formulation for these models, considering oblique light directions. These models lead to more complex nonlinear partial differential equations of Hamilton-Jacobi type which we are able to describe in a unified framework. The construction of approximate (weak) solutions ar...
Direct Differential Photometric Stereo Shape Recovery of Diffuse and Specular Surfaces
Journal of Mathematical Imaging and Vision, 2016
Recovering the 3D shape of an object from shading is a challenging problem due to the complexity of modeling light propagation and surface reflections. Photometric Stereo (PS) is broadly considered a suitable approach for high-resolution shape recovery, but its functionality is restricted to a limited set of object surfaces and controlled lighting setup. In particular, PS models generally consider reflection from objects as purely diffuse, with specularities being regarded as a nuisance that breaks down shape reconstruction. This is a serious drawback for implementing PS approaches since most common materials have prominent specular components. In this paper, we propose a PS model that solves the problem for both diffuse and specular components aimed at shape recovery of generic objects with the approach being independent of the albedo values
Reconstructing shape from shading images under point light source illumination
[1990] Proceedings. 10th International Conference on Pattern Recognition, 1990
A new photometric method is proposed f o r determining the 3-D shape of t h e object from multiple shading Images under t h e point light source illumination. When t h e surface is t h e perfect diffuser with t h e uniform reflectance, an algorithm f o r the determination of 3-D shape with positions is developed by using t h e method of least squares and basing on the principle of the monocular vision and the inverse square law f o r illuminance. In t h e proposed method, the number of the necessary images is four f o r the general surface, and can be reduced t o three for t h e continuous surface.
Image and Vision Computing, 2007
This paper presents a new multi-light source photometric stereo system for reconstructing images of various characteristics of non-Lambertian rough surfaces with widely varying texture and specularity. Compared to the traditional three-light photometric stereo method, extra lights are employed using a hierarchical selection strategy to eliminate the effects of shadows and specularities, and to make the system more robust. We also show that six lights is the minimum needed in order to apply photometric stereo to the entire visible surface of any convex object. Experiments on synthetic and real scenes demonstrate that the proposed method can extract surface reflectance and orientation effectively, even in the presence of strong shadows and highlights. Hence, the method offers advantages in the recovery of dichromatic surfaces possessing rough texture or deeply relieved topographic features, with applications in reverse engineering and industrial surface inspection. Experimental results are presented in the paper. Published by Elsevier B.V.
Reconstruction of three-dimensional surfaces from two-dimensional binary images
This paper describes a method for reconstruction of threedimensional visible and invisible opaque surfaces using moving shadows. An object whose shape is to be determined is placed on a reference surface. A beam of substantially parallel rays of light is projected at the object at a set of different angles relative to the reference surface. Using a camera which is placed above the reference surface, the shadows cast by the object for each angle are transferred to a computer. A threedimensional binary level shadow diagram (JDBL Shadowgram) is formed and analyzed. The Shadowgram has some features which make the reconstruction very simple: a section of the 3DBL Shadowgram, referred to as a LDBL Shadowgram, can be used to determine the heights of points of the object to be reconstructed. Further analysis of some curves of the Shadowgram can he used for the partial reconstruction of invisible surfaces.