Transfinite interpolation

In numerical analysis, transfinite interpolation is a means to construct functions over a planar domain in such a way that they match a given function on the boundary. This method is applied in geometric modelling and in the field of finite element method. ^[1]

The transfinite interpolation method, first introduced by William J. Gordon and Charles A. Hall,^[2] receives its name due to how a function belonging to this class is able to match the primitive function at a nondenumerable number of points.^[3] In the authors' words:

“

We use the term ‘transfinite’ to describe the general class of interpolation schemes studied herein since, unlike the classical methods of higher dimensional interpolation which match the primitive function F at a finite number of distinct points, these methods match F at a non-denumerable (transfinite) number of points.

”

Formula

With parametrized curves ${\vec {c}}_{1}(u)$ , ${\vec {c}}_{3}(u)$ describing one pair of opposite sides of a domain, and ${\vec {c}}_{2}(v)$ , ${\vec {c}}_{4}(v)$ describing the other pair. the position of point (u,v) in the domain is

${\begin{array}{rcl}{\vec {S}}(u,v)&=&(1-v){\vec {c}}_{1}(u)+v{\vec {c}}_{3}(u)+(1-u){\vec {c}}_{2}(v)+u{\vec {c}}_{4}(v)\\&&-\left[(1-u)(1-v){\vec {P}}_{1,2}+uv{\vec {P}}_{3,4}+u(1-v){\vec {P}}_{1,4}+(1-u)v{\vec {P}}_{3,2}\right]\end{array}}$

where, e.g., ${\vec {P}}_{1,2}$ is the point where curves ${\vec {c}}_{1}$ and ${\vec {c}}_{2}$ meet.

References

↑ Dyken, Christopher; Floater, Michael S. (2009). "Transfinite mean value interpolation". Computer Aided Geometric Design. 1 (26): 117–134. doi:10.1016/j.cagd.2007.12.003.
↑ Gordon, William; Hall, Charles (1973). "Construction of curvilinear coordinate systems and application to mesh generation". International Journal for Numerical Methods in Engineering. 7: 461–177. doi:10.1002/nme.1620070405.
↑ Gordon, William; Thiel, Linda (1982). "Transfinite mapping and their application to grid generation". Applied Mathematics and Computation (10): 171–233. doi:10.1016/0096-3003(82)90191-6.

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