#173 Fix bug when super-triangle does not contain vertices

artem-ogre · May 2, 2024 · b9d761e · b9d761e
1 parent 58f34da
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diff --git a/CDT/include/Triangulation.hpp b/CDT/include/Triangulation.hpp
@@ -988,8 +988,12 @@ void Triangulation<T, TNearPointLocator>::addSuperTriangle(const Box2d<T>& box)
         (box.min.x + box.max.x) / T(2), (box.min.y + box.max.y) / T(2)};
     const T w = box.max.x - box.min.x;
     const T h = box.max.y - box.min.y;
-    T r = std::sqrt(w * w + h * h) / T(2); // incircle radius
-    r = r > 0 ? r * T(1.1) : T(1e-6);
+    T r = std::max(w, h); // incircle radius upper bound
+
+    // Note: make sure radius is big enough. Constants chosen experimentally.
+    // - for tiny bounding boxes: use 1.0 as the smallest radius
+    // - multiply radius by 2.0 for extra safety margin
+    r = std::max(T(2) * r, T(1));
 
     // Note: for very large floating point numbers rounding can lead to wrong
     // super-triangle coordinates. This is a very rare corner-case so the
@@ -999,8 +1003,9 @@ void Triangulation<T, TNearPointLocator>::addSuperTriangle(const Box2d<T>& box)
             r *= T(2);
     }
 
-    const T R = T(2) * r;                        // excircle radius
-    const T shiftX = R * std::sqrt(T(3)) / T(2); // R * cos(30 deg)
+    const T R = T(2) * r;                    // excircle radius
+    const T cos_30_deg = 0.8660254037844386; // note: (std::sqrt(3.0) / 2.0)
+    const T shiftX = R * cos_30_deg;
     const V2d<T> posV1 = {center.x - shiftX, center.y - r};
     const V2d<T> posV2 = {center.x + shiftX, center.y - r};
     const V2d<T> posV3 = {center.x, center.y + R};

diff --git a/CDT/tests/cdt.test.cpp b/CDT/tests/cdt.test.cpp
@@ -945,3 +945,17 @@ TEST_CASE("Regression test: hanging edge in pseudo-poly", "")
     cdt.insertEdges(ee);
     REQUIRE(CDT::verifyTopology(cdt));
 }
+
+TEST_CASE("Regression test #174: super-triangle of tiny bounding box", "")
+{
+    auto cdt = Triangulation<double>{};
+    const auto vv = Vertices<double>{
+        {{45802.2779561576462583616375923, 169208.540894783218391239643097},
+         {45802.2779561576317064464092255, 169208.540894783218391239643097},
+         {45802.2779561576462583616375923, 169208.540894783247495070099831}},
+    };
+    REQUIRE_NOTHROW(cdt.insertVertices(vv));
+    REQUIRE(CDT::verifyTopology(cdt));
+    cdt.eraseSuperTriangle();
+    REQUIRE(cdt.triangles.size() == std::size_t(1));
+}
diff --git a/CDT/tests/expected/cdt__as-provided_ignore_all.txt b/CDT/tests/expected/cdt__as-provided_ignore_all.txt
@@ -1,61 +1,61 @@
 203
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-1 63 59   14 142 0
-1 64 63   15 146 13
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-2 3 51   17 26 23
-2 4 3   18 24 16
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-2 6 5   20 29 18
-2 7 6   21 31 19
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-2 9 8   1 34 21
-2 51 65   16 108 12
-3 4 41   17 28 25
+0 1 59   4294967295 12 10
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 3 41 42   24 92 26
-3 42 51   25 93 16
-4 5 40   18 30 28
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 4 40 41   27 92 24
-5 6 39   19 31 30
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 5 39 40   29 90 27
-6 7 39   20 33 29
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 7 38 39   32 90 31
-8 9 37   22 37 35
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 8 37 38   34 89 32
-9 10 36   2 39 37
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 9 36 37   36 87 34
-10 11 35   3 41 39
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 10 35 36   38 86 36
-11 12 34   4 43 41
+11 12 34   3 43 41
 11 34 35   40 82 38
-12 13 33   5 45 43
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 12 33 34   42 77 40
-13 14 32   6 47 45
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 13 32 33   44 76 42
-14 15 31   7 49 47
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 14 31 32   46 81 44
-15 16 30   8 51 49
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 15 30 31   48 80 46
-16 17 29   9 53 51
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 16 29 30   50 80 48
-17 18 28   10 55 53
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 17 28 29   52 79 50
 18 19 27   56 57 55
 18 27 28   54 75 52
-18 59 19   11 58 54
+18 59 19   10 58 54
 19 20 27   59 62 54
 19 59 70   56 141 60
 19 69 20   60 63 57
@@ -141,12 +141,12 @@
 57 77 76   129 169 138
 58 59 60   141 142 128
 58 70 59   132 58 140
-59 63 60   13 144 140
+59 63 60   12 144 140
 60 62 61   144 145 125
 60 63 62   142 146 143
 61 62 66   143 148 126
-62 63 64   144 14 147
-62 64 65   146 15 148
+62 63 64   144 13 147
+62 64 65   146 14 148
 62 65 66   147 108 145
 67 83 82   150 179 114
 67 84 83   151 181 149

diff --git a/CDT/tests/expected/cdt__as-provided_resolve_all.txt b/CDT/tests/expected/cdt__as-provided_resolve_all.txt
@@ -1,61 +1,61 @@
 203
-0 1 59   4294967295 13 11
-0 9 2   2 22 4294967295
-0 10 9   3 36 1
-0 11 10   4 38 2
-0 12 11   5 40 3
-0 13 12   6 42 4
-0 14 13   7 44 5
-0 15 14   8 46 6
-0 16 15   9 48 7
-0 17 16   10 50 8
-0 18 17   11 52 9
-0 59 18   0 56 10
-1 2 65   4294967295 23 15
-1 63 59   14 142 0
-1 64 63   15 146 13
-1 65 64   12 147 14
-2 3 51   17 26 23
-2 4 3   18 24 16
-2 5 4   19 27 17
-2 6 5   20 29 18
-2 7 6   21 31 19
-2 8 7   22 32 20
-2 9 8   1 34 21
-2 51 65   16 108 12
-3 4 41   17 28 25
+0 1 59   4294967295 12 10
+0 10 2   2 22 4294967295
+0 11 10   3 38 1
+0 12 11   4 40 2
+0 13 12   5 42 3
+0 14 13   6 44 4
+0 15 14   7 46 5
+0 16 15   8 48 6
+0 17 16   9 50 7
+0 18 17   10 52 8
+0 59 18   0 56 9
+1 2 65   4294967295 23 14
+1 63 59   13 142 0
+1 64 63   14 146 12
+1 65 64   11 147 13
+2 3 51   16 26 23
+2 4 3   17 24 15
+2 5 4   18 27 16
+2 6 5   19 29 17
+2 7 6   20 31 18
+2 8 7   21 32 19
+2 9 8   22 34 20
+2 10 9   1 36 21
+2 51 65   15 108 11
+3 4 41   16 28 25
 3 41 42   24 92 26
-3 42 51   25 93 16
-4 5 40   18 30 28
+3 42 51   25 93 15
+4 5 40   17 30 28
 4 40 41   27 92 24
-5 6 39   19 31 30
+5 6 39   18 31 30
 5 39 40   29 90 27
-6 7 39   20 33 29
-7 8 38   21 35 33
+6 7 39   19 33 29
+7 8 38   20 35 33
 7 38 39   32 90 31
-8 9 37   22 37 35
+8 9 37   21 37 35
 8 37 38   34 89 32
-9 10 36   2 39 37
+9 10 36   22 39 37
 9 36 37   36 87 34
-10 11 35   3 41 39
+10 11 35   2 41 39
 10 35 36   38 86 36
-11 12 34   4 43 41
+11 12 34   3 43 41
 11 34 35   40 82 38
-12 13 33   5 45 43
+12 13 33   4 45 43
 12 33 34   42 77 40
-13 14 32   6 47 45
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 13 32 33   44 76 42
-14 15 31   7 49 47
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 16 29 30   50 80 48
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 18 27 28   54 75 52
-18 59 19   11 58 54
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 19 20 27   59 62 54
 19 59 70   56 141 60
 19 69 20   60 63 57
@@ -141,12 +141,12 @@
 57 77 76   129 169 138
 58 59 60   141 142 128
 58 70 59   132 58 140
-59 63 60   13 144 140
+59 63 60   12 144 140
 60 62 61   144 145 125
 60 63 62   142 146 143
 61 62 66   143 148 126
-62 63 64   144 14 147
-62 64 65   146 15 148
+62 63 64   144 13 147
+62 64 65   146 14 148
 62 65 66   147 108 145
 67 83 82   150 179 114
 67 84 83   151 181 149