Extraction of surface quad layouts from quad layout immersions: application to an isogeometric model of car crash

Extraction of quadrilateral layouts of surfaces is essential for surface rebuilding using splines, semi-structured bilinear quadrilateral mesh extraction, and texture mapping. Layout generation using integer grid based techniques on triangulated meshes have received particular attention for generation of well-structured layouts. In this work, we reiterate a generalization of integer grid parameterizations in which only topological constraints between singularities are necessary to ensure a valid quadrilateral parameterization (and specifically, the integral curves emanating from singularities are of finite length). This generalized representation is motivated by carefully discussing pros and cons of both integer grid and topologically constrained parameterization methods. A computational framework for extracting a quadrilateral layout from a valid input immersion is then presented, which will work for any parameterization that induces a valid quadrilateral layout. Results demonstrate the validity and the potential of the proposed computational framework on a variety of geometries. The proposed extraction framework is ultimately used to reconstruct the body-in-white of a 1996 Dodge Neon as a set of analysis-suitable bicubic B-splines, which are then used in the first known body-in-white crash analysis using boundary-conforming splines, demonstrating that the reconstruction method is viable for industrial use.