• Title/Summary/Keyword: Barycentric transformation

Search Result 3, Processing Time 0.018 seconds

ON BARYCENTRIC TRANSFORMATIONS OF FANO POLYTOPES

  • Hwang, DongSeon;Kim, Yeonsu
    • Bulletin of the Korean Mathematical Society
    • /
    • v.58 no.5
    • /
    • pp.1247-1260
    • /
    • 2021
  • We introduce the notion of barycentric transformation of Fano polytopes, from which we can assign a certain type to each Fano polytope. The type can be viewed as a measure of the extent to which the given Fano polytope is close to be Kähler-Einstein. In particular, we expect that every Kähler-Einstein Fano polytope is of type B. We verify this expectation for some low dimensional cases. We emphasize that for a Fano polytope X of dimension 1, 3 or 5, X is Kähler-Einstein if and only if it is of type B.

Geodesics-based Shape-preserving Mesh Parameterization (직선형 측지선에 기초한 원형보전형 메쉬 파라미터화)

  • 이혜영
    • Journal of KIISE:Computer Systems and Theory
    • /
    • v.31 no.7
    • /
    • pp.414-420
    • /
    • 2004
  • Among the desirable properties of a piecewise linear parameterization, guaranteeing a one-to-one mapping (i.e., no triangle flips in the parameter plane) is often sought. A one-to-one mapping is accomplished by non-negative coefficients in the affine transformation. In the Floater's method, the coefficients were computed after the 3D mesh was flattened by geodesic polar-mapping. But using this geodesic polar map introduces unnecessary local distortion. In this paper, a simple variant of the original shape-preserving mapping technique by Floater is introduced. A new simple method for calculating barycentric coordinates by using straightest geodesics is proposed. With this method, the non-negative coefficients are computed directly on the mesh, reducing the shape distortion introduced by the previously-used polar mapping. The parameterization is then found by solving a sparse linear system, and it provides a simple and visually-smooth piecewise linear mapping, without foldovers.

Spectral Reflectivity Recovery from Tristimulus Values Using 3D Extrapolation with 3D Interpolation

  • Kim, Bog G.;Werner, John S.;Siminovitch, Michael;Papamichael, Kostantinos;Han, Jeongwon;Park, Soobeen
    • Journal of the Optical Society of Korea
    • /
    • v.18 no.5
    • /
    • pp.507-516
    • /
    • 2014
  • We present a hybrid method for spectral reflectivity recovery, using 3D extrapolation as a supplemental method for 3D interpolation. The proposed 3D extrapolation is an extended version of 3D interpolation based on the barycentric algorithm. It is faster and more accurate than the conventional spectral-recovery techniques of principal-component analysis and nonnegative matrix transformation. Four different extrapolation techniques (based on nearest neighbors, circumcenters, in-centers, and centroids) are formulated and applied to recover spectral reflectivity. Under the standard conditions of a D65 illuminant and 1964 $10^{\circ}$ observer, all reflectivity data from 1269 Munsell color chips are successfully reconstructed. The superiority of the proposed method is demonstrated using statistical data to compare coefficients of correlation and determination. The proposed hybrid method can be applied for fast and accurate spectral reflectivity recovery in image processing.