To the Graduate Council: I am submitting herewith a dissertation ...

Chapter 2: Related Work 14heuristics were also used in this work to achieve robustness to missing and unreliabledata. Eggert et al [Eggert96] used both point position and normal information in thesearch for correspondences. All the views were represented in a single coordinateframe, and the search was performed on the combined point sets.Using analogy to physics Eggert et al [Eggert96], and stoddart et al [Stoddart96]devised a force-based optimization method to register the data sets. The closest pointswere connected by springs assuring better convergence to local minima. Formulatingthe multiple-views registration problem in graph theoretic framework, Neugebauer etal [Neugebauer97] represented the different datasets as nodes and the transformationsas links. The registration task in this approach consisted of finding a network withbalanced registration errors. For improved computational efficiency, a multi-resolutionhierarchical approach was adopted, where the number of points used at the start is lowand increases as the registration proceeds. A similar graph theoretical algorithm wasproposed by Huber and Hebert [Huber03]. Recently a hybrid algorithm employinginvariant features was used to enhance the performance of the standard ICP [Sharp02].The search for closest matches was performed in the extended positional and featurespace. For recent surveys and comparisons of several common variants of the ICPalgorithm the following references [Dalley02][Rodrigues02][Rusinkiewicz01] can beconsulted.Several researchers studied the relationship between surface shape complexity and theregistration accuracy. In this context, Pennec and Thirion [Pennec97] characterized theuncertainty of point set registration. Stoddart et al [Stoddart96] defined a registrationindex measuring shape information, and Brujic and Ristic [Brujic96] used MonteCarlo simulation to study the dependence of accuracy and complexity. To enhance thealignment in the case of scenes with low shape information content, Pito [Pito97]designed a registration aid that can be placed with the scanned objects ensuring precisematching.