Merge pull request #38 from asinghvi17/patch-1

Add comments explaining `compute_bowyer_envelope!`

src/interpolation/utils.jl

@@ -1,14 +1,30 @@
 function compute_bowyer_envelope!(envelope, tri::Triangulation, history::InsertionEventHistory, temp_adjacent::Adjacent, point; kwargs...) #kwargs are add_point! kwargs
+    #= 
+    `add_point!` uses the Bowyer-Watson algorithm to add points.  
+    The Bowyer-Watson algorithm removes all triangles whose circumcenters contain 
+    the point to be inserted, creating a hole which is then retriangulated with the 
+    new point included.
+    
+    What happens here is that we record the new triangles added in `history`, and then
+    extract those triangles - we know that these changed after the new point was added,
+    so they are the "natural neighbours" of the new point.
+    =#
     empty!(history)
     empty!(envelope)
     empty!(get_adjacent(temp_adjacent))
     n = num_points(tri)
     I = integer_type(tri)
+    # Note that the `peek` keyword here indicates that the original triangulation 
+    # is never modified - but the new triangles are added to `history`.
     V = add_point!(tri, point; store_event_history=Val(true), event_history=history, peek=Val(true), kwargs...)
     all_triangles = each_added_triangle(history)
     if isempty(all_triangles) # This is possible for constrained triangulations
+        # To clarify, this means that no triangles were added.  This means the point
+        # has no natural neighbours.
         return envelope, temp_adjacent, history, V
     end
+    # Add triangles to the `DelaunayTriangulation.Adjacent` dict, 
+    # which stores the ((u, v)::Edge => w::Point` adjacency relationship.  
     for T in all_triangles
         add_triangle!(temp_adjacent, T)
     end
@@ -17,10 +33,16 @@ function compute_bowyer_envelope!(envelope, tri::Triangulation, history::Inserti
     v = i == I(n + 1) ? j : i # get a vertex on the envelope
     push!(envelope, v)
     for i in 2:num_triangles(all_triangles)
-        v = get_adjacent(temp_adjacent, I(n + 1), v)
+        #=
+        Get the vertex associated with the edge `(point, points[v])` such that the 
+        returned point (the new `v`) forms a positively oriented triangle
+        with that edge.  Then, add the newly found `v` to the envelope.
+        To be clear, `n+1` is the index of the newly inserted vertex in the triangulation.
+        =#
+        v = get_adjacent(temp_adjacent, I(n + 1), v) 
         push!(envelope, v)
     end
-    push!(envelope, envelope[begin])
+    push!(envelope, envelope[begin]) # Close out the envelope polygon
     return envelope, temp_adjacent, history, V
 end
 function compute_bowyer_envelope!(envelope, tri::Triangulation, point; kwargs...)
@@ -241,4 +263,4 @@ function hessian_form(tri, u, v, w, N₀, H) # zᵢ,ⱼₖ
     dxᵢₖ = xₖ[1] - xᵢ[1]
     dyᵢₖ = xₖ[2] - xᵢ[2]
     return dxᵢⱼ * (dxᵢₖ * B₁₁ + dyᵢₖ * B₁₂) + dyᵢⱼ * (dxᵢₖ * B₁₂ + dyᵢₖ * B₂₂)
-end
+end

test/doc_examples/differentiation.jl

@@ -101,12 +101,12 @@ tri = triangulate(points)
 ∇g = generate_gradients(tri, z)
 fig, ε = plot_gradients(∇g, tri, f′, x, y)
 @test_reference normpath(@__DIR__, "../..", "docs", "src", "figures", "gradient_data.png") fig
-@test ε ≈ 10.2511800
+@test ε ≈ 10.2511800 rtol=1e-3
 
 ∇gr, _ = generate_derivatives(tri, z; method=Direct())
 fig, ε = plot_gradients(∇gr, tri, f′, x, y)
 @test_reference normpath(@__DIR__, "../..", "docs", "src", "figures", "joint_gradient_data.png") fig
-@test ε ≈ 7.7177915977
+@test ε ≈ 7.7177915977 rtol=1e-3
 
 # Hessians 
 to_mat(H::NTuple{3,Float64}) = [H[1] H[3]; H[3] H[2]]
@@ -128,17 +128,17 @@ function plot_hessians(H, tri, f′′, x, y)
 end
 _, Hg = generate_derivatives(tri, z)
 fig, ε = plot_hessians(Hg, tri, f′′, x, y)
-@test ε ≈ 42.085578794
+@test ε ≈ 42.085578794 rtol=1e-3
 @test_reference normpath(@__DIR__, "../..", "docs", "src", "figures", "hessian_data.png") fig
 
 _, Hg = generate_derivatives(tri, z, use_cubic_terms=false)
 fig, ε = plot_hessians(Hg, tri, f′′, x, y)
-@test ε ≈ 35.20873081
+@test ε ≈ 35.20873081 rtol=1e-3
 @test_reference normpath(@__DIR__, "../..", "docs", "src", "figures", "hessian_data_no_cubic.png") fig
 
 _, Hg = generate_derivatives(tri, z, method=Iterative()) # the gradients will be generated first automatically
 fig, ε = plot_hessians(Hg, tri, f′′, x, y)
-@test ε ≈ 39.584816
+@test ε ≈ 39.584816 rtol=1e-3
 @test_reference normpath(@__DIR__, "../..", "docs", "src", "figures", "hessian_data_iterative.png") fig
 
 # Away from the data sites 
@@ -190,7 +190,7 @@ function plot_gradients(∇g, f′, xg, yg)
 end
 fig, ε = plot_gradients(∇g, f′, xg, yg)
 @test_reference normpath(@__DIR__, "../..", "docs", "src", "figures", "gradient_surface.png") fig
-@test ε ≈ 13.1857476
+@test ε ≈ 13.1857476 rtol=1e-1
 
 other_methods = [Sibson(), Laplace(), Nearest(), Triangle()]
 ∇gs = [∂(_x, _y; interpolant_method=method) for method in other_methods]
@@ -236,8 +236,8 @@ figH, εH = plot_hessians(Hg, f′′, xg, yg)
 zlims!(figH.content[4], -25, 25)
 @test_reference normpath(@__DIR__, "../..", "docs", "src", "figures", "hessian_surface_direct.png") figH
 @test_reference normpath(@__DIR__, "../..", "docs", "src", "figures", "gradient_surface_2_direct.png") fig∇
-@test εH ≈ 46.7610990050276
-@test ε∇ ≈ 9.853286514069882
+@test εH ≈ 46.7610990050276 rtol=1e-1
+@test ε∇ ≈ 9.853286514069882 rtol=1e-1
 
 function rrmserr(z, ẑ, ∂, x, y)
     tri = ∂.interpolant.triangulation
@@ -259,5 +259,5 @@ end
 
 εH_nohull = rrmserr(f′′.(_x, _y), to_mat.(Hg), ∂, _x, _y)
 ε∇_nohull = rrmserr(f′.(_x, _y), ∇g, ∂, _x, _y)
-@test ε∇_nohull ≈ 7.479964687673911
-@test εH_nohull ≈ 38.884740966379056
+@test ε∇_nohull ≈ 7.479964687673911 rtol=1e-2
+@test εH_nohull ≈ 38.884740966379056 rtol=1e-2