Reconstruction and Geometric Algorithms - Romain Vergne

Property of empty circumscribed circles. Page 78. Delaunay Triangulation. Properties. Property of empty circumscribed circles. Page 79. Delaunay Triangulation.
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Reconstruction and Geometric Algorithms Romain Vergne 2014 - 2015

PLAN • Introduction • Parameterized / Ordered data – Curve Interpolation – Surface Interpolation – Curve Approximation – Surface Approximation

PLAN • Introduction • Parameterized / Ordered data – Curve Interpolation – Surface Interpolation

Point Interpolation Parametric Functions

Linear

Shepard

Shepard

Polynomial

Point Interpolation Parametric Functions

Hermite Interpolation

Spline

Point Interpolation Parametric Functions

Shepard

Bilinear

Shepard

Polynomial

Point Interpolation Parametric Functions

Tensor Product

Curve Interpolation Parametric Functions Linear

Coons

Hermite

Laplace/Poisson Interpolation Functions f( x, y ) = z

Original

3D Version

10%

3D Version

Laplace Interpolation Functions f( x, y ) = z

PLAN • Introduction • Parameterized / Ordered data – Curve Interpolation – Surface Interpolation – Curve Approximation – Surface Approximation

Subdivision Curves • Repeatedly refine the control polygon – P1  P2  P3  P4 …….

• Curve is the limit of an infinite process

Subdivision Curves

Chaikin 1

Catmull-Clark (approx)

Chaikin 2

Catmull-Clark (interp)

Subdivision Surfaces

Subdivision Loop

Butterfly Subdivision

Catmull-Clark Subdivision

Subdivision Surfaces For real-time applications?

PN triangles

Phong tessellation

Least Squares

Principal Component Analysis

On two random variables x and y

Principal Component Analysis

On an image

Total Least Squares

Comparison

Moving Least Squares

w = Gaussian function

PLAN • Introduction • Parameterized / Ordered data • Reconstruction of non-organized data – Explicit Methods – Implicit Methods

Convex Hull Incremental

Convex Hull Incremental

Convex Hull Incremental

Convex Hull Incremental

Convex Hull Incremental

Convex Hull Incremental

Convex Hull Incremental

Convex Hull Incremental

Convex Hull Incremental

Convex Hull Incremental

Convex Hull Incremental

Convex Hull Incremental

Convex Hull Incremental

Convex Hull Quick Hull

Convex Hull Quick Hull

Convex Hull Quick Hull

Convex Hull Quick Hull

Convex Hull Quick Hull

Convex Hull Quick Hull

Convex Hull Quick Hull

Convex Hull Quick Hull

Convex Hull Quick Hull

Convex Hull Quick Hull

Convex Hull Quick Hull

Convex Hull Quick Hull

Convex Hull Quick Hull

Convex Hull Quick Hull

Convex Hull Quick Hull

Voronoi diagram

Voronoi diagram

Voronoi diagram

Voronoi diagram

Voronoi diagram

Voronoi diagram

Voronoi diagram

Voronoi diagram

Voronoi diagram

Voronoi diagram

Natural neighbor interpolation: (Obramov): http://pirlwww.lpl.arizona.edu/~abramovo/MOLA_interpolation/interpolation_paper/interpolation_paper.html

Voronoi diagram

Voronoi diagram

Voronoi diagram Green and Sibson

Voronoi diagram Green and Sibson

Voronoi diagram Green and Sibson

Demo: http://alexbeutel.com/webgl/voronoi.html

Voronoi diagram

Voronoi diagram

Voronoi diagram

Voronoi diagram

Weighted voronoi diagram Okabe et al. 1992

Weighted voronoi diagram

Secord, 2002

Weighted voronoi diagram

Secord, 2002

Delaunay Triangulation Properties

Delaunay Triangulation Properties

Voronoi Diagram of Ѵ of E

Delaunay Triangulation Properties

Delaunay Triangulation Ϯ of E

Delaunay Triangulation Properties

Delaunay Triangulation Ϯ of E

Delaunay Triangulation Properties

Property of empty circumscribed circles

Delaunay Triangulation Properties

Property of empty circumscribed circles

Delaunay Triangulation Properties

Property of empty circumscribed circles

Delaunay Triangulation Properties

Property of empty circumscribed circles

Delaunay Triangulation Properties

Property of empty circumscribed circles

Delaunay Triangulation Properties

Property of empty circumscribed circles

Delaunay Triangulation Properties

Property of empty circumscribed circles

Delaunay Triangulation Properties

Property of empty circumscribed circles

Delaunay Triangulation Properties

Property of empty circumscribed circles

Delaunay Triangulation Properties

Property of empty circumscribed circles

Delaunay Triangulation Properties

Center of circumscribed circles = Vertices of Voronoi diagram

Delaunay Triangulation Properties

Center of circumscribed circles = Vertices of Voronoi diagram

Delaunay Triangulation Properties

Example of non-Delaunay triangulation

Delaunay Triangulation Properties

Example of non-Delaunay triangulation

Delaunay Triangulation Incremental Algorithm We consider an initial triangulation and you want to add P – find the triangle containing P – destroy the triangles that pose problem – construct new triangles – add new triangles to the initial triangulation

Delaunay Triangulation Algorithm Flip – Compute any triangulation – While there exist non-Delaunay triangles • Flip edges

Delaunay Triangulation Construction by Convex Hull

Points Pi( xi, yi )

Delaunay Triangulation Construction by Convex Hull

Points Pi projected( xi, yi , Pi.Pi)

Delaunay Triangulation Construction by Convex Hull

Convex hull of Pi

Delaunay Triangulation Construction by Convex Hull

Lower Convex hull of Pi

Delaunay Triangulation Construction by Convex Hull

Project points on the plane z=0

Delaunay Triangulation Construction by Convex Hull

Elipse: project plan on convex hull

Delaunay Triangulation Construction by Convex Hull

Projected ellipse: circumscribed circle of the triangle

Delaunay Triangulation Construction by Convex Hull

Delaunay triangulation (dim d) = convex hull (dim d+1)

Crust algorithm (2D)

Crust algorithm (2D)

Crust algorithm (2D)

Crust algorithm (2D)

Crust algorithm (2D)

Crust algorithm (2D)

Crust algorithm (2D)

Crust algorithm (3D)

Bibliography • Cours de Nicolas Szafran 2011/2012 (http://www-ljk.imag.fr/membres/Nicolas.Szafran/) • Scattered Data Interpolation and Approximation for Computer Graphics (Siggraph Asia course 2010) • Implicit surface reconstruction from point clouds (Johan Huysmans’s thesis) • http://www.cise.ufl.edu/~sitharam/COURSES/ CG/kreveldmorevoronoi.pdf