Sketch-based interactive shape deformation using shading isophotes

De plus en plus d'importance est accordée à la création d'objets 3D en raison des récents essors technologiques. Il est donc crucial de fournir des outils appropriés et accessibles aux utilisateurs de tous les horizons. Malheureusement, les outils traditionnellement utilisés en création 3D sont conçus pour des professionnels, exigent des formations complexes et de longue durée, et ne sont pas adaptés à ceux inexperimentés qui forment la vaste majorité des utilisateurs potentiels. Nous proposons un outil de création simplifié qui utilise des méthodes inspirées d'esquisses. Dans un premier temps, le maillage désiré est créé à partir d'un contour tracé. L'intérieur est gonflé suivant la méthode de Dvoroznak et al. Dans un deuxième temps, la hauteur des sommets du maillage est manipulée en modifiant les courbes formées par l'ombrage. Cet ombrage provient d'un modèle de réflexion Lambertien pour une lumière directionnelle donnée. Notre méthode consiste à utiliser les courbes formées par la méthode des charactéristiques associée au problème de figure dérivée de l'ombre (Shape-From-Shading). Avec les courbes, nous identifions les régions affectées par la modification de l'ombrage. L'une de ces régions sera utilisée pour interpoler l'ombrage d'après la nouvelle isophote. À partir de ce nouvel ombrage, les courbes de la méthode des characteristiques seront utilisées afin de trouver le nouveau déplacement en s'assurant d'altérer uniquement la région affectée par le changement dans l'ombrage. Les maillages créés peuvent ensuite être combinés suivant la méthode proposée par Dvoroznak et al. afin de former un maillage unique et complexe. Notre outil se veut plus intuitif que les outils traditionnels de création. Nos résultats en illustrent le potentiel.Due to recent technological advances, the creation of 3D objects is becoming more important. It is critical to offer appropriate and accessible tools to users from diverse backgrounds. Unfortunately, the tools traditionally used in 3D creation are designed for professionals, require complex and time-consuming training, and are unsuitable for inexperienced users who form the vast majority of potential users. We propose a simplified creation tool that uses sketch-based methods. First, the desired mesh is created from a traced outline. The interior is inflated following the method of Dvoroznak et al. Second, the height (displacement) of the mesh is achieved by altering the strips created by shading. Shading is the result of a Lambertian reflection model for a given directional light. Our method consists of using the strips from the method of characteristics applied to solve Shape-From-Shading. Using the strips, we identify the regions affected by the change in shading. One of these regions will be used to interpolate the shading according to the new isophote. From this new shading, the characteristic strips will be used to find the new height, ensuring that only the region affected by the change in shading is altered. The meshes created can then be combined, inspired by the method proposed by Dvoroznak et al. to form a single, complex mesh. Our tool is designed to be more intuitive than the ones provided by professional 3D software. Our results illustrate its potential

Shape from shading with non-parallel light source.

by Siu-Yuk Yeung.Thesis (M.Phil.)--Chinese University of Hong Kong, 1999.Includes bibliographical references (leaves 96-102).Abstracts in English and Chinese.Chapter 1 --- Introduction --- p.5Chapter 1.1 --- Shape recovery techniques --- p.5Chapter 1.2 --- Shape from Shading algorithms --- p.8Chapter 1.2.1 --- Some developments on surface reflection --- p.9Chapter 1.2.2 --- Some developments on computing methods --- p.11Chapter 1.2.3 --- Some developments on light source model --- p.12Chapter 1.3 --- Proposed algorithms in this thesis --- p.13Chapter 1.4 --- Thesis outline --- p.14Chapter 2 --- Camera and surface reflectance models for SFS --- p.15Chapter 2.1 --- Camera models for SFS --- p.16Chapter 2.1.1 --- Pinhole camera model and perspective projection --- p.17Chapter 2.1.2 --- Approximations of perspective projection --- p.20Chapter 2.2 --- Surface reflectance models for SFS --- p.22Chapter 2.2.1 --- Lambertian surface model --- p.23Chapter 2.2.2 --- Bidirectional Reflectance Distribuction Function --- p.23Chapter 2.3 --- Summary --- p.25Chapter 3 --- Review of some related SFS algorithms --- p.26Chapter 3.1 --- The SFS algorithm proposed by Bichsel and Pentland --- p.27Chapter 3.1.1 --- Determine surface height with a minimum downhill principle --- p.28Chapter 3.1.2 --- Implementation on a discrete grid --- p.30Chapter 3.2 --- The SFS algorithm proposed by Kimmel and Bruckstein --- p.31Chapter 3.2.1 --- Level set propagation --- p.32Chapter 3.2.2 --- Problem formulation --- p.33Chapter 3.2.3 --- Equal height contour propagation using level set method --- p.35Chapter 3.3 --- Summary --- p.36Chapter 4 --- Multiple extended light source models for SFS --- p.38Chapter 4.1 --- Three extended light source models for SFS --- p.40Chapter 4.1.1 --- Rectangular light source model --- p.40Chapter 4.1.2 --- Spherical light source model --- p.43Chapter 4.1.3 --- Cylindrical light source model --- p.48Chapter 4.2 --- SFS for an extended light source --- p.53Chapter 4.3 --- Multiple extended light source model --- p.53Chapter 4.4 --- Simulation and experiment result --- p.54Chapter 4.5 --- Error Analysis --- p.55Chapter 4.5.1 --- Descriptions of the error --- p.55Chapter 4.5.2 --- Errors for different light models --- p.55Chapter 4.6 --- Summary --- p.57Chapter 5 --- Global SFS for an endoscope image --- p.70Chapter 5.1 --- Introduction --- p.71Chapter 5.2 --- Local SFS algorithm for endoscope image --- p.73Chapter 5.2.1 --- Imaging system and brightness formulation --- p.74Chapter 5.2.2 --- Equal distance contour propagation and shape reconstruc- tion --- p.75Chapter 5.3 --- Global SFS algorithm for endoscope image --- p.76Chapter 5.3.1 --- A global shape from shading algorithm for a parallel light --- p.77Chapter 5.3.2 --- The relationship between depth map and distance map --- p.78Chapter 5.3.3 --- A global shape from shading algorithm for endoscope image --- p.78Chapter 5.4 --- Simulations and experiments results --- p.83Chapter 5.5 --- Summary --- p.86Chapter 6 --- Summary and conclusion --- p.87Chapter 6.1 --- Problems tackled in this thesis --- p.87Chapter 6.2 --- Discussion on future developments --- p.8