diff --git a/Advancing_front_surface_reconstruction/doc/Advancing_front_surface_reconstruction/Advancing_front_surface_reconstruction.txt b/Advancing_front_surface_reconstruction/doc/Advancing_front_surface_reconstruction/Advancing_front_surface_reconstruction.txt index cc1c8f99f59..2a9475f56fa 100644 --- a/Advancing_front_surface_reconstruction/doc/Advancing_front_surface_reconstruction/Advancing_front_surface_reconstruction.txt +++ b/Advancing_front_surface_reconstruction/doc/Advancing_front_surface_reconstruction/Advancing_front_surface_reconstruction.txt @@ -30,10 +30,10 @@ In most surface based Delaunay algorithms the triangles are selected independently, that is in parallel \cgalCite{agj-lcsr-00}\cgalCite{ab-srvf-98}. This chapter presents a surface-based Delaunay surface -reconstruction algorithm by selecting the triangles sequentially, that -is by using previous selected triangles to select a new triangle for +reconstruction algorithm that sequentially selects the triangles, that +is it uses previously selected triangles to select a new triangle for advancing the front. At each advancing step the most plausible -triangle is selected, and the triangles are selected in a way that +triangle is selected, and such that the triangles selected generates an orientable manifold triangulated surface. Two other examples of this greedy approach are the ball pivoting @@ -53,16 +53,16 @@ We describe next the algorithm and provide examples. A detailed description of the algorithm and the underlying theory are provided in \cgalCite{cgal:csd-gdbsra-04}. - The first step of the algorithm is the construction of a 3D Delaunay -triangulation of the point set. The Delaunay triangle with the -smallest radius is the starting point for the greedy algorithm. The -radius of a triangle \f$ t \f$ is the radius of the smallest sphere +triangulation of the point set. +The radius of a triangle \f$ t \f$ is the radius of the smallest sphere passing through the vertices of \f$ t\f$ and enclosing no sample point. In other words, the radius \f$ r_t\f$ is the distance from any vertex of \f$ t\f$ to the Voronoi edge dual to \f$ t\f$. This triangle with three boundary edges is the initial triangulated surface, and its boundary is the advancing front. +The Delaunay triangle with the smallest radius is the starting point +for the greedy algorithm. The algorithm maintains a priority queue of candidate triangles, that is of valid triangles incident to the boundary edges of the current @@ -77,7 +77,7 @@ which are explained next. \subsection AFSR_Topology Topological Constraints -Any triangle \f$t\f$ considered as next potential candidate shares an +Any triangle \f$t\f$ considered as the next potential candidate shares an edge \f$e\f$ with the front of the current reconstruction. Let \f$b\f$ be the vertex of \f$t\f$ opposite to \f$e\f$. There are four configurations where \f$t\f$ is added to the surface. @@ -105,15 +105,15 @@ radius. While the radius is a good criterion in the case of 2D smooth curve reconstruction \cgalCite{b-cccda-94}, we need another criterion for 3D surface reconstruction, namely the dihedral angle between triangles on the surface, that is the angle between the normals of the -triangles. - +triangles. There are two bounds namely \f$ \alpha_\mathrm{sliver} \f$ +and \f$ \beta \f$. We denote by \f$ \beta_t\f$ the angle between the normal of a triangle \f$ t\f$ incident on a boundary edge \f$ e \f$ and the normal of the triangle on the surface incident to \f$ e \f$. The *candidate* triangle of an edge \f$ e \f$ is the triangle -with the smallest radius, that is valid for \f$ e \f$ +with the smallest radius that is valid for \f$ e \f$ and that has \f$ \beta_t < \alpha_\mathrm{sliver} \f$. There may be no such triangle. In the implementation of the algorithm \f$ \alpha_\mathrm{sliver} = 5\pi/6 \f$.