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T-splines

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T-splines
NameT-splines
TypeSpline surface representation
DeveloperTimothy A. Sederberg
Firstappeared2000s
RelatedNURBS, B-spline, subdivision surface, Bézier

T-splines.

Overview

T-splines are a spline-based surface representation developed for geometric modeling and computer graphics that unifies concepts from Bézier curve, B-spline, NURBS, subdivision surface, Non-uniform rational B-spline, Bezier surface, Catmull–Clark subdivision, Gregory patch, Isogeometric analysis, and parametric surface traditions. They were introduced to address limitations arising in Automotive design, Aerospace engineering, Shipbuilding, Industrial design, Architectural design and Entertainment industry modeling pipelines. Key proponents and institutions associated with T-splines include Timothy A. Sederberg, Autodesk, Carnegie Mellon University, University of Utah, Georgia Institute of Technology, National Institute of Standards and Technology and Maya (software). The representation bridges workflows used by Rhinoceros 3D, SolidWorks, CATIA, Siemens NX, PTC Creo, Blender, and Autodesk 3ds Max.

Mathematical Foundations

Mathematical foundations of T-splines draw on results from Spline (mathematics), Bernstein polynomial, Linear algebra, Numerical analysis, Approximation theory, Functional analysis, Differential geometry, Tensor product, Piecewise polynomial, and Finite element method. A T-spline surface is defined by a control grid and a set of blending functions built from local knot vectors analogous to those in NURBS and B-spline. The basis functions obey partition of unity and local support properties familiar from work by Isaac Jacob Schoenberg, Carl de Boor, G. de Boor, I. J. Schoenberg, A. Schoenberg and Henri de Villiers. Continuity conditions (Ck continuity) and evaluation formulas connect to theory developed by C. de Boor, Philippe G. Ciarlet, John C. Strikwerda and other researchers in Numerical linear algebra and Approximation theory.

Construction and Algorithms

Construction algorithms for T-splines involve topology-aware knot assignment, patch extraction, and evaluation techniques influenced by algorithms from de Boor algorithm, Bézier extraction, B-spline refinement, knot insertion, knot removal, knot refinement, k-d tree, bilinear interpolation, and multiresolution analysis. Algorithms for local refinement, T-mesh manipulation, and conversion to NURBS or subdivision surfaces employ strategies introduced by Timothy A. Sederberg, Ying He, Mario Botsch, Leif Kobbelt, Jörg Peters, Scott Schaefer, David Baraff, F. P. Preparata, Michael Kass, and Jim Blinn. Numerical stability, basis evaluation, and trimming are addressed using methods from Adaptive subdivision, Bezier clipping, Isogeometric analysis, and Quadrature techniques that reference work by Thomas J.R. Hughes, Andreas Dedner and Ansgar Reusken.

Applications in Computer-Aided Design and Modeling

T-splines are applied extensively in Automotive industry surface modeling, Aerospace industry structural and aerodynamic surface design, Shipbuilding hull fairing, Consumer electronics enclosure design, Jewelry design, Character modeling for Pixar, Walt Disney Animation Studios, Industrial Light & Magic, Video game asset creation for Electronic Arts, Ubisoft, Activision Blizzard and Epic Games, and Architectural design for firms like Zaha Hadid Architects and SOM (architecture firm). They are used in workflows integrating Rhinoceros 3D, Grasshopper (computational design), Autodesk Fusion 360, SolidWorks, CATIA, Siemens NX, PTC Creo, Blender, Maya (software), 3ds Max, and Substance (software). In engineering contexts T-splines support Isogeometric analysis coupling with finite element meshes for work by Thomas J.R. Hughes, J. Austin Cottrell, Y. Bazilevs, T.J.R. Hughes and Matthias Wohlmuth.

Implementation and Software

Commercial and academic implementations exist in Autodesk, Rhinoceros 3D, McNeel & Associates, Siemens PLM Software, Dassault Systèmes, PTC, SolidWorks Corporation, Blender Foundation, Pixar, and research code from Carnegie Mellon University, University of Utah, Georgia Institute of Technology, ETH Zurich, RWTH Aachen University, University of British Columbia and University of Toronto. Plugins and libraries include integrations for RhinoCommon, OpenNURBS, OpenCASCADE, CGAL, Eigen (software), OpenGL, Vulkan, DirectX, CUDA, and OpenMP. File exchange and interoperability target formats used by STEP (ISO 10303), IGES, ACIS (file format), OBJ (geometry format), FBX, and PLY (file format).

Advantages, Limitations, and Comparisons

Advantages cited include local refinement without global mesh refinement, reduced control-point count compared to tensor-product NURBS, and compatibility with Isogeometric analysis and subdivision methods developed by Hughes group, Jörg Peters, Leif Kobbelt, Mario Botsch and Scott Schaefer. Limitations encompass challenges in robust trimming, T-mesh degeneracies, and conversion complexity addressed in work by Timothy A. Sederberg, Xin Li, Rongjun Chen, Thomas J.R. Hughes, Ying He, and J. A. Cottrell. Comparisons with NURBS, subdivision surface, Subdivision, B-spline, and Gregory patch approaches are common in literature from ACM SIGGRAPH, IEEE Visualization, Euromed, ASME, AIAA, and IFIP conferences.

History and Standardization

T-splines originated in the early 2000s with principal contributions from Timothy A. Sederberg, Mridul A. Srinivasan and collaborators at Brigham Young University and were commercialized through partnerships with Autodesk and McNeel & Associates. Standardization efforts intersected with ISO, ASTM International, W3C, and software vendors such as Dassault Systèmes, Siemens PLM Software and PTC aiming for interoperability with STEP (ISO 10303). Key presentations and papers appeared in proceedings of ACM SIGGRAPH, ACM Transactions on Graphics, Computer Aided Geometric Design, SIAM Journal on Numerical Analysis, IEEE Computer Graphics and Applications and CAGD workshops. Ongoing research continues at institutions including Carnegie Mellon University, University of Utah, ETH Zurich, Georgia Institute of Technology, University of British Columbia, and RWTH Aachen University.

Category:Computer graphics