NURBS
Non-Uniform Rational B-Splines — the dominant mathematical representation for surface-oriented CAD. A NURBS entity is defined by degree, control points, a knot vector, and an evaluation rule. Moving a control point affects only the adjacent spans (local support), preserving design intent elsewhere.
In context
When a Class-A automotive surface designer creates a hood in CATIA's Generative Shape Design, the resulting geometry is stored as NURBS surfaces — allowing downstream Abaqus simulation to evaluate panel stiffness using the exact mathematical surface rather than a faceted mesh approximation. NURBS also enables the exact representation of circles and cylinders in CAD, which is why a pipe cross-section in engineering drawings is mathematically exact, not a polygon approximation.
Why it matters
NURBS is why Rhino, CATIA, and Class-A automotive surfaces look the way they do. The rational qualifier means NURBS can represent exact conics — circles, ellipses, parabolas — that non-rational splines approximate only approximately.
Related concepts
External References
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Cite this definition
Finocchiaro, Michael. “NURBS.” DemystifyingPLM PLM Glossary, 2026, https://www.demystifyingplm.com/glossary/nurbs