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Fix planar hull with several poins in the start/end sweep line #281

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Nov 28, 2021
Merged

Fix planar hull with several poins in the start/end sweep line #281

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7fb6323
Fix planar hull with several poins in the start/end sweep line
blegat Nov 27, 2021
08a0bd5
Fixes
blegat Nov 28, 2021
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20 changes: 19 additions & 1 deletion src/planar.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -17,7 +17,7 @@ function getsemihull(ps::Vector{PT}, sign_sense, counterclockwise, yray::Nothing
psj_vec = ps[j] - prev
cc = counterclockwise(cur_vec, psj_vec)
if isapproxzero(cc)
# `cur` and `ps[j]` are on the same ray from `cur`.
# `cur` and `ps[j]` are on the same ray starting from `prev`.
# The one that is closer to `prev` is redundant.
# If `j` is the last index and redundant (it may happen if this
# ray is perpendicular to the direction of sorting) then we should
Expand All @@ -29,6 +29,7 @@ function getsemihull(ps::Vector{PT}, sign_sense, counterclockwise, yray::Nothing
elseif cc < 0
break
end
# `cur` is redundant so `cur` is dropped and `prev` becomes `cur`
cur = prev
pop!(hull)
if !isempty(hull)
Expand Down Expand Up @@ -124,6 +125,23 @@ function _planar_hull(d::FullDim, points, lines, rays, counterclockwise, rotate)
sweep_norm = rotate(coord(line))
end
sort!(points, by = x -> dot(x, sweep_norm))

if !isempty(points)
# `getsemihull` fails if `points` starts or end with several points on the same sweep line that are not ordered clockwise
start_line = dot(points[1], sweep_norm)
# `isapprox` won't work well with `atol=0` (which is the default) if `start_line` is zero, so we set a nonzero `atol`.
# TODO We should also multiply it with a scaling.
end_start = something(findfirst(x -> !isapprox(dot(x, sweep_norm), start_line, atol=Base.rtoldefault(typeof(start_line))), points), length(points) + 1) - 1
if end_start > 1
sort!(view(points, 1:end_start), by = x -> counterclockwise(x, sweep_norm), rev=true)
end
end_line = dot(points[end], sweep_norm)
start_end = something(findlast(x -> !isapprox(dot(x, sweep_norm), end_line, atol=Base.rtoldefault(typeof(start_line))), points), 0) + 1
if start_end < length(points)
sort!(view(points, start_end:length(points)), by = x -> counterclockwise(x, sweep_norm))
end
end

_points = eltype(points)[]
_lines = eltype(lines)[]
_rays = eltype(rays)[]
Expand Down
27 changes: 23 additions & 4 deletions test/planar.jl
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Expand Up @@ -8,7 +8,7 @@ function test_planar_square(VT, d)
no = -ei[1] - ei[2]
ne = ei[1] - ei[2]
se = ei[1] + ei[2]
expected = [no, so, se, ne]
expected = [ne, no, so, se]
for ps in [
[no, so, ne, se],
[no, se, so, ne],
Expand Down Expand Up @@ -61,7 +61,7 @@ end

# Square + redundant points + [+-1.5, -+0.25]
function test_planar_square_with_more()
expected = [[-1.0, -1.0], [-1.0, 1.0], [1.0, 1.0], [1.0, -1.0]]
expected = [[1.0, -1.0], [-1.0, -1.0], [-1.0, 1.0], [1.0, 1.0]]
v0 = convexhull([-1.0, -1.0], [1.0, -1.0], [-1.0, 1.0], [1.0, 1.0], [0.0, 1.0])
v1 = Polyhedra.planar_hull(v0)
@test collect(points(v1)) == expected
Expand All @@ -71,11 +71,11 @@ function test_planar_square_with_more()
v0 = convexhull([0.0, 1.0 + 1e-10], [-1.0, -1.0], [1.0, -1.0], [-1.0, 1.0], [1.0, 1.0])
v1 = Polyhedra.planar_hull(v0)
@test collect(points(v1)) == expected
expected = [[-1.0, -1.0], [-1.0, 1.0], [0.0, 1.0 + 1e-4], [1.0, 1.0], [1.0, -1.0]]
expected = [[1.0, -1.0], [-1.0, -1.0], [-1.0, 1.0], [0.0, 1.0 + 1e-4], [1.0, 1.0]]
v0 = convexhull([-1.0, -1.0], [1.0, -1.0], [-1.0, 1.0], [1.0, 1.0], [0.0, 1.0 + 1e-4])
v1 = Polyhedra.planar_hull(v0)
@test collect(points(v1)) == expected
expected = [[-1.0, -1.0], [-1.5, 0.25], [-1.0, 1.0], [1.0, 1.0], [1.5, -0.25], [1.0, -1.0]]
expected = [[1.0, -1.0], [-1.0, -1.0], [-1.5, 0.25], [-1.0, 1.0], [1.0, 1.0], [1.5, -0.25]]
v0 = convexhull([-1.0, -1.0], [1.0, -1.0], [-1.0, 1.0], [1.0, 1.0], [0.0, 1.0], [-1.5, 0.25], [1.5, -0.25])
v1 = Polyhedra.planar_hull(v0)
@test collect(points(v1)) == expected
Expand All @@ -90,11 +90,30 @@ function test_planar_square_with_more()
@test collect(points(v1)) == expected
end

function test_issue_271()
expected = [[1.0, 0.0], [-0.5, 0.0], [0.5, 0.5]]
v = convexhull([0.0, 0.0], [1, 0], [0.5, 0.0], [-0.5, 0.0], [0.5, 0.5])
p = Polyhedra.planar_hull(v)
@test collect(points(p)) == expected
v = convexhull([1, 0], [0.0, 0.0], [0.5, 0.0], [-0.5, 0.0], [0.5, 0.5])
p = Polyhedra.planar_hull(v)
@test collect(points(p)) == expected

expected = [[1.0, 0.0], [-0.5, 0.0], [0.0, 0.5], [1.0, 0.5]]
v = vrep([[1, 0], [0.0, 0.0], [0.5, 0.0], [-0.5, 0.0], [0.5, 0.5], [1.0, 0.5], [0.0, 0.5], [0.2, 0.5]])
p = Polyhedra.planar_hull(v)
@test collect(points(p)) == expected
v = vrep([[1, 0], [0.0, 0.0], [0.5, 0.0], [-0.5, 0.0], [1.0, 0.5], [0.2, 0.5], [0.5, 0.5], [0.0, 0.5]])
p = Polyhedra.planar_hull(v)
@test collect(points(p)) == expected
end

@testset "Planar" begin
for T in [Float64, Int]
for (VT, d) in [(Vector{T}, 2), (SVector{2, T}, StaticArrays.Size(2))]
test_planar_square(VT, d)
end
end
test_planar_square_with_more()
test_issue_271()
end