Suraj R. Musuvathy Riesenfeld/Cohen Lab, Warnock Eng. Bldg. School of Computing University of Utah Salt Lake City, Utah 84112 email: srm 'at' cs 'dot' utah 'dot' edu

I am currently a PhD student working with Elaine Cohen in the Geometric Design and Computation (GDC) research group. My research interests include geometric feature extraction and shape analysis using B-Spline techniques for applications in computer-aided design and engineering (CAD) and medical imaging. I have also worked on virtual environments for reverse CAD engineering.

I am a recipient of the 2010-2011 University of Utah Graduate Research Fellowship.

Research

	"Principal Curvature Ridges and Geometrically Salient Regions of Parametric B-Spline Surfaces", Computer-Aided Design 2010 (accepted for publication). Ridges are characteristic curves of a surface that mark salient intrinsic features of its shape and are therefore valuable for shape matching, surface quality control, visualization and various other applications. Ridges are loci of points on a surface where one of the principal curvatures attain a critical value in its respective principal direction. We present a new algorithm for accurately extracting ridges on B-Spline surfaces and define a new type of salient region corresponding to major ridges that characterize geometrically significant regions on surfaces. Ridges exhibit complex behavior near umbilics on a surface, and may also pass through certain turning points causing added complexity for ridge computation. We present a new numerical tracing algorithm for extracting ridges that also accurately captures ridge behavior at umbilics and ridge turning points. The algorithm traverses ridge segments by detecting ridge points while advancing and sliding in principal directions on a surface in a novel manner, thereby computing connected curves of ridge points. The output of the algorithm is a set of curve segments, some or all of which, may be selected for other applications such as those mentioned above. The results of our technique are validated by comparison with results from previous research and with a brute-force domain sampling technique.
	"Ridge Extraction from Isosurfaces of Volumetric Data using Implicit B-Splines", SMI 2010. Ridges on a surface are extremal curves of principal curvatures of the surface that indicate salient intrinsic features of its shape. This paper presents a novel approach for extracting ridges of improved quality from isosurfaces of volumetric scalar-valued grids by converting them to implicit trivariate B-spline representations. A robust tracing approach demonstrated to extract ridges accurately from parametric B-spline surfaces is extended to extract ridges from the implicit representations. Ridges extracted directly from smooth surface representations using the proposed tracing approach are accurate and hence smoother, connected ridge curves as compared to approaches that extract ridges directly from discrete representations. This approach can also be used to extract ridges directly from smooth representations such as isosurfaces of volumetric B-Spline CAD models and algebraic functions, and extended to extract ridges from polygonal meshes, as demonstrated in the paper. Most of the existing approaches for ridge extraction address only crests, a certain subset of the ridges on a surface. The approach presented in this paper enables extraction of all types of generic ridges on a surface thereby presenting a complete solution.
	"Extracting Principal Curvature Ridges from B-Spline Surfaces with Deficient Smoothness", Springer-Verlag Lecture Notes in Computer Science (ISVC 2009). Principal curvature ridges identify characteristic feature curves on a surface that can be used for surface registration, quality control, visualization and various other shape interrogation applications across disciplines such as medical imaging, computer vision, computer-aided design and engineering and geology. Current techniques for accurate extraction of ridges from B-Spline surfaces require $C^n$, $n \geq 3$ smoothness. In practice, many fitting techniques and modeling systems yield surface representations that may be only $C^2$, $C^1$ or $C^0$ on the knot lines. In this paper, we generalize a robust tracing algorithm to address the problem of extracting ridges from surfaces with lower orders of smoothness to broaden its applicability to a much larger set of surfaces.
	"Tracing Ridges on B-Spline Surfaces", SIAM/ACM GDSPM 2009 ( Best Paper Award ). Ridges are characteristic curves of a surface that mark salient intrinsic features of its shape and are therefore valuable for shape matching, surface quality control, visualization and various other applications. Ridges are loci of points on a surface where either of the principal curvatures attain a critical value in its respective principal direction. These curves have complex behavior near umbilics on a surface, and may also pass through certain turning points causing added complexity for ridge computation. We present a new algorithm for numerically tracing ridges on B-Spline surfaces that also accurately captures ridge behavior at umbilics and ridge turning points. The algorithm traverses ridge segments by detecting ridge points while advancing and sliding in principal directions on a surface in a novel manner, thereby computing connected curves of ridge points. The output of the algorithm is a set of curve segments, some or all of which, may be selected for other applications such as those mentioned above. The results of our technique are validated by comparison with results from previous research and with a brute-force domain sampling technique.
	Reverse engineering is a time-consuming and technically formidable process that is increasingly becoming an economic imperative due to replacement costs. The {\em Multiple Engineering Resources aGent Environment} (MERGE) system, introduced in this paper, is a new approach toward reverse engineering whose architecture and modules are driven specifically by the requirements of {\em legacy engineering}. Legacy engineering scenarios presume availability of multiple (possibly incomplete or inconsistent) sources of information, lack of digital descriptions of the parts, constrained time restrictions and need for significant domain knowledge expertise. The reverse engineering process must yield modern CAD models capable of driving state-of-the art CAM processes. The MERGE system aims at making the reverse engineering process more effective, using both intuitive interaction and visualization as key components, by enabling quick identification and resolution of inconsistencies among various resources in a unified environment. The MERGE system also aims at simplifying the reverse engineering process by integrating various {\em computational agents} to assist the reverse engineer in processing information and in creating the desired CAD models. "Integrating Multiple Engineering Resources in a Virtual Environment for Reverse Engineering Legacy Mechanical Parts". ASME IDETC/CIE, 2005. (pdf) "A Virtual Environment for Legacy Mechanical Systems Engineering". MS Thesis, University of Utah, 2006. (pdf)