Using more than three shading images gives more This paper proposes a new method to recover the sign of local Gaussian curvature from multiple shading images (more than three). The required information to recover the sign of Gaussian curvature is obtained by applying Principal Components Analysis (PCA) to the normalized irradiance measurements. The sign of the Gaussian curvature is recovered ba...

Linear, Discrete, and Quadratic Constraints in Single-Image 3D Reconstruction Ady Ecker Doctor of Philosophy Graduate Department of Computer Science University of Toronto 2010 In this thesis, we investigate the formulation, optimization and ambiguities in single-image 3D surface reconstruction from geometric and photometric constraints. We examine linear, discrete and quadratic constraints for ...

The human visual system is proficient in perceiving three-dimensional shape from the shading patterns in a two-dimensional image. How it does this is not well understood and continues to be a question of fundamental and practical interest. In this paper we present a new quantitative approach to shape-from-shading that may provide some answers. We suggest that the brain, through evolution or pri...

We address the problem of integrating multi-frame stereo and shading cues within the framework of optimization in the infinite-dimensional space of piecewise smooth surfaces. Cue integration then reduces to the determination of regions where prior assumptions on the reflectance of the surfaces can be enforced. By combining cues, our formulation allows defining a well-posed problem even when rec...

We investigated shape constancy in human shape from shading under variations of illuminant direction using a local attitude probe in conjunction with a perturbation analysis. Stimuli were computer generated and depicted ellipsoids in a structured setting. Even with these simple shapes subjects settings were systematically biased in the illuminant direction and were consistent with a regression ...

In this paper, a method for estimating parameters of a 3-D shape from a 2-D shading image using a genetic algorithms (GAs) is proposed. The shape of the object is represented by a superquadrics model, and then the model parameters are coded for being applied to GAs. The coded string is evaluated according to the similarity of the shading image calculated from the 3D model shape represented by t...

We introduce a variational method for multi-view shapefrom-shading under natural illumination. The key idea is to couple PDE-based solutions for single-image based shapefrom-shading problems across multiple images and multiple color channels by means of a variational formulation. Rather than alternatingly solving the individual SFS problems and optimizing the consistency across images and chann...

Direct volume rendering is a commonly used technique in visualization applications. Many of these applications require sophisticated shading models to capture subtle lighting effects and characteristics of volumetric data and materials. For many volumes, homogeneous regions pose problems for typical gradient based surface shading. Many common objects and natural phenomena exhibit visual quality...

Shading and classification are among the most powerful and important techniques used in volume rendering. Unfortunately, for hardware accelerated volume rendering based on OpenGL, direct classification was previously only supported on SGI platforms and shading could only be approximated inaccurately, resulting in artifacts mostly visible in darkening. In this paper, we present a novel approach ...