Added ability to create a Triangulation with only points and triangles as input (#192)

Co-authored-by: Daniel VandenHeuvel <[email protected]>

Author: matgrand

NEWS.md

@@ -1,5 +1,9 @@
 # Changelog
 
+## 1.5.0
+
+- Introduced the ability to reconstruct unconstrained triangulations from an existing set of points and triangles using `Triangulation(points, triangles)`. See [#192](https://github.com/JuliaGeometry/DelaunayTriangulation.jl/pull/192)
+
 ## 1.4.0
 
 - Updated to AdaptivePredicates.jl v1.2, now allowing caches to be passed to the predicates involving `incircle` and `orient3`. These are only useful when using the `AdaptiveKernel()` kernel. Outside of triangulating, these caches are not passed by default, but can be provided. The functions `get_incircle_cache` and `get_orient3_cache` can be used for this purpose on a triangulation (without a triangulation, refer to AdaptivePredicate.jl's `incircleadapt_cache` and `orient3adapt_cache`). See [#185](https://github.com/JuliaGeometry/DelaunayTriangulation.jl/pull/185).

Project.toml

@@ -1,7 +1,7 @@
 name = "DelaunayTriangulation"
 uuid = "927a84f5-c5f4-47a5-9785-b46e178433df"
 authors = ["Daniel VandenHeuvel <[email protected]>"]
-version = "1.4.2"
+version = "1.5.0"
 
 [deps]
 AdaptivePredicates = "35492f91-a3bd-45ad-95db-fcad7dcfedb7"

src/data_structures/triangulation/triangulation.jl

@@ -488,7 +488,7 @@ Returns the `Triangulation` corresponding to the triangulation of `points` with
 
 # Arguments 
 - `points`: The points that the triangulation is of. 
-- `triangles`: The triangles of the triangulation. These should be given in counter-clockwise order, with vertices corresponding to `points`. These should not include any ghost triangles.
+- `triangles`: The triangles of the triangulation. These should be given in counter-clockwise order, with vertices corresponding to `points`. Ghost triangles should not be included (and are ignored if they are).
 - `boundary_nodes`: The boundary nodes of the triangulation. These should match the specification given in the documentation or in [`check_args`](@ref).
 
 # Keyword Arguments 
@@ -520,6 +520,52 @@ Returns the `Triangulation` corresponding to the triangulation of `points` with
     return build_triangulation_from_data!(tri, triangles, _bn, delete_ghosts, predicates)
 end
 
+"""
+    Triangulation(points, triangles; kwargs...) -> Triangulation
+
+Returns the unconstrained `Triangulation` corresponding to the triangulation of `points` with `triangles`.
+
+!!! note "Valid boundary"
+
+    This constructor uses the [`convex_hull`](@ref) of `points` to determine the triangulation's boundary.
+    If the set of triangles does not form a valid unconstrained triangulation, then this constructor may not
+    return a valid triangulation. Similarly, if there is a point in `points` that is not a vertex of some 
+    triangle, but is a vertex of the convex hull, the triangulation will not be valid.
+
+# Arguments 
+- `points`: The points that the triangulation is of. There should not be any points not referenced in `triangles`.
+- `triangles`: The triangles of the triangulation. These should be given in counter-clockwise order, with vertices corresponding to `points`. Ghost triangles should not be included (and are ignored if they are).
+
+# Keyword Arguments 
+- `predicates::AbstractPredicateKernel=AdaptiveKernel()`: Method to use for computing predicates. Can be one of [`FastKernel`](@ref), [`ExactKernel`](@ref), and [`AdaptiveKernel`](@ref). See the documentation for a further discussion of these methods.
+- `IntegerType=Int`: The integer type to use for the triangulation. This is used for representing vertices.
+- `EdgeType=isnothing(segments) ? NTuple{2,IntegerType} : (edge_type ∘ typeof)(segments)`: The edge type to use for the triangulation. 
+- `TriangleType=NTuple{3,IntegerType}`: The triangle type to use for the triangulation.
+- `EdgesType=isnothing(segments) ? Set{EdgeType} : typeof(segments)`: The type to use for storing the edges of the triangulation.
+- `TrianglesType=Set{TriangleType}`: The type to use for storing the triangles of the triangulation.
+- `weights=ZeroWeight()`: The weights associated with the triangulation. 
+- `delete_ghosts=false`: Whether to delete the ghost triangles after the triangulation is computed. This is done using [`delete_ghost_triangles!`](@ref).
+
+# Output 
+- `tri`: The [`Triangulation`](@ref).
+"""
+@inline function Triangulation(
+    points::P, triangles::T;
+    IntegerType::Type{I}=Int,
+    EdgeType::Type{E}=NTuple{2,IntegerType},
+    TriangleType::Type{V}=NTuple{3,IntegerType},
+    EdgesType::Type{Es}=Set{EdgeType},
+    TrianglesType::Type{Ts}=Set{TriangleType},
+    weights=ZeroWeight(),
+    delete_ghosts=false,
+    predicates::AbstractPredicateKernel=AdaptiveKernel(),
+) where {P,T,I,E,V,Es,Ts}
+    bn = get_vertices(convex_hull(points; predicates, IntegerType))
+    tri = Triangulation(points, triangles, bn; IntegerType, EdgeType, TriangleType, EdgesType, TrianglesType, weights, delete_ghosts, predicates)
+    unlock_convex_hull!(tri)
+    return tri
+end
+
 """
     build_triangulation_from_data!(tri::Triangulation, triangles, boundary_nodes, delete_ghosts, predicates::AbstractPredicateKernel=AdaptiveKernel())
 
@@ -540,6 +586,7 @@ See the documentation for more information about these choices.
     graph = get_graph(tri)
     tris = get_triangles(tri)
     for τ in each_triangle(triangles)
+        is_ghost_triangle(τ) && continue
         add_triangle!(adj, τ)
         add_triangle!(adj2v, τ)
         add_triangle!(graph, τ)

test/data_structures/triangulation.jl

@@ -1475,3 +1475,13 @@ end
         end
     end
 end
+
+@testset "Constructor with only points and triangles" begin
+    points = [(0.0, 0.0), (0.87, 0.0), (1.0006, 0.7766), (0.0, 1.0), (0.5, 0.5)]
+    tri1 = triangulate(points)
+    triangles = tri1.triangles
+    tri2 = DT.Triangulation(points, triangles)
+    @test validate_triangulation(tri2)
+    @test tri1 == tri2
+    @test !DT.has_boundary_nodes(tri2)
+end

test/triangulation/triangulate.jl

@@ -36,4 +36,4 @@ end
             @test validate_triangulation(tri; predicates = PT())
         end
     end
-end
+end