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feat: generate triangle colors utility
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@andywiecko
andywiecko committed Mar 1, 2025
1 parent a92dd60 commit e91de32
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Showing 2 changed files with 130 additions and 10 deletions.
70 changes: 64 additions & 6 deletions Runtime/Triangulator.cs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -763,12 +763,9 @@ public static class Utilities
/// <param name="allocator">The allocator to use for temporary data.</param>
public static void GenerateHalfedges(Span<int> halfedges, ReadOnlySpan<int> triangles, Allocator allocator)
{
CheckAndThrowIfLengthNotEqual(halfedges, triangles);
ThrowCheckGenerateHalfedges(halfedges, triangles);

for (int i = 0; i < halfedges.Length; i++)
{
halfedges[i] = -1;
}
halfedges.Fill(-1);

using var tmp = new NativeHashMap<int2, int>(triangles.Length, allocator);
for (int he = 0; he < halfedges.Length; he++)
Expand All @@ -790,6 +787,56 @@ public static void GenerateHalfedges(Span<int> halfedges, ReadOnlySpan<int> tria
}
}

/// <summary>
/// Generates triangle <paramref name="colors"/> using the provided <paramref name="halfedges"/>.
/// Triangles that share a common edge are assigned the same color index.
/// The resulting <paramref name="colors"/> contains values in the range <tt>[0, <paramref name="colorsCount"/>)</tt>.
/// Check the documentation for further details.
/// </summary>
/// <param name="colors">A buffer that will be populated with triangle colors. Its length must be three times smaller than <paramref name="halfedges"/>.</param>
/// <param name="halfedges">The halfedge data used for generating colors.</param>
/// <param name="colorsCount">The total number of unique colors assigned.</param>
/// <param name="allocator">The allocator to use for temporary data.</param>
/// <seealso cref="GenerateHalfedges(Span{int}, ReadOnlySpan{int}, Allocator)"/>
public static void GenerateTriangleColors(Span<int> colors, ReadOnlySpan<int> halfedges, out int colorsCount, Allocator allocator)
{
ThrowCheckGenerateTriangleColors(colors, halfedges);

colorsCount = 0;
colors.Fill(-1);

using var heQueue = new NativeQueueList<int>(allocator);
for (int t = 0; t < colors.Length; t++)
{
if (colors[t] == -1)
{
heQueue.Enqueue(3 * t + 0);
heQueue.Enqueue(3 * t + 1);
heQueue.Enqueue(3 * t + 2);
colors[t] = colorsCount;
BFS(colorsCount++, colors, heQueue, halfedges);
}
}

static void BFS(int color, Span<int> colors, NativeQueueList<int> heQueue, ReadOnlySpan<int> halfedges)
{
while (heQueue.TryDequeue(out var he))
{
var ohe = halfedges[he];
var t = ohe / 3;
if (ohe == -1 || colors[t] != -1)
{
continue;
}

heQueue.Enqueue(3 * t + 0);
heQueue.Enqueue(3 * t + 1);
heQueue.Enqueue(3 * t + 2);
colors[t] = color;
}
}
}

/// <summary>
/// Inserts a sub-mesh, defined by (<paramref name="subpositions"/>, <paramref name="subtriangles"/>), into the main mesh
/// represented by (<paramref name="positions"/>, <paramref name="triangles"/>).
Expand Down Expand Up @@ -837,7 +884,7 @@ public static unsafe void InsertSubMesh<T>(NativeList<T> positions, NativeList<i
public static int NextHalfedge(int he) => he % 3 == 2 ? he - 2 : he + 1;

[System.Diagnostics.Conditional("ENABLE_UNITY_COLLECTIONS_CHECKS")]
private static void CheckAndThrowIfLengthNotEqual(ReadOnlySpan<int> halfedges, ReadOnlySpan<int> triangles)
private static void ThrowCheckGenerateHalfedges(ReadOnlySpan<int> halfedges, ReadOnlySpan<int> triangles)
{
if (halfedges.Length != triangles.Length)
{
Expand All @@ -846,6 +893,17 @@ private static void CheckAndThrowIfLengthNotEqual(ReadOnlySpan<int> halfedges, R
);
}
}

[System.Diagnostics.Conditional("ENABLE_UNITY_COLLECTIONS_CHECKS")]
private static void ThrowCheckGenerateTriangleColors(ReadOnlySpan<int> colors, ReadOnlySpan<int> halfedges)
{
if (3 * colors.Length != halfedges.Length)
{
throw new ArgumentException(
$"The provided colors[{colors.Length}] must be one-third of the length of halfedges [{halfedges.Length}]."
);
}
}
}
}

Expand Down
70 changes: 66 additions & 4 deletions Tests/UtilitiesTests.cs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -47,10 +47,9 @@ public int[] GenerateHalfedgesTest(int[] triangles)
}

[Test]
public void GenerateHalfedgesThrowIfDifferentLengthTest()
{
Assert.Throws<ArgumentException>(() => Utilities.GenerateHalfedges(new int[4], new int[7], Allocator.Persistent));
}
public void GenerateHalfedgesThrowTest() => Assert.Throws<ArgumentException>(() =>
Utilities.GenerateHalfedges(halfedges: new int[4], triangles: new int[7], Allocator.Persistent)
);

private static readonly TestCaseData[] nextHalfedgeTestData =
{
Expand Down Expand Up @@ -116,5 +115,68 @@ public int[] InsertSubMeshTest((float2[] p, int[] t) mesh, (float2[] p, int[] t)
Assert.That(positions.AsArray(), Is.EqualTo(mesh.p.Concat(subMesh.p)));
return triangles.AsReadOnly().ToArray();
}

private static readonly TestCaseData[] generateTriangleColorsTestData =
{
new(new int[]{ }, 0)
{
ExpectedResult = new int[]{ },
TestName = "Test case 0 - 0 triangles 0 colors (GenerateTriangleColorsTest)"
},
new(new int[]{ -1, -1, -1 }, 1)
{
ExpectedResult = new int[]{ 0 },
TestName = "Test case 1 - 1 triangle 1 color (GenerateTriangleColorsTest)"
},
new(new int[]{ -1, -1, -1, -1, -1, -1 }, 2)
{
ExpectedResult = new int[]{ 0, 1 },
TestName = "Test case 2a - 2 triangles 2 colors (GenerateTriangleColorsTest)"
},
new(new int[]{ 3, -1, -1, 0, -1, -1 }, 1)
{
ExpectedResult = new int[]{ 0, 0 },
TestName = "Test case 2b - 2 triangles 1 colors (GenerateTriangleColorsTest)"
},
new(new int[]{ -1, -1, -1, -1, -1, -1, -1, -1, -1 }, 3)
{
ExpectedResult = new int[]{ 0, 1, 2 },
TestName = "Test case 3a - 3 triangles 3 colors (GenerateTriangleColorsTest)"
},
new(new int[]{ 3, -1, -1, 0, -1, -1, -1, -1, -1 }, 2)
{
ExpectedResult = new int[]{ 0, 0, 1 },
TestName = "Test case 3b - 3 triangles 2 colors (GenerateTriangleColorsTest)"
},
new(new int[]{ 6, -1, -1, -1, -1, -1, 0, -1, -1 }, 2)
{
ExpectedResult = new int[]{ 0, 1, 0 },
TestName = "Test case 3c - 3 triangles 2 colors (GenerateTriangleColorsTest)"
},
new(new int[]{ -1, -1, -1, 6, -1, -1, 3, -1, -1 }, 2)
{
ExpectedResult = new int[]{ 0, 1, 1 },
TestName = "Test case 3d - 3 triangles 2 colors (GenerateTriangleColorsTest)"
},
new(new int[]{ 3, -1, -1, 0, 6, -1, 4, -1, -1 }, 1)
{
ExpectedResult = new int[]{ 0, 0, 0 },
TestName = "Test case 3e - 3 triangles 1 color (GenerateTriangleColorsTest)"
},
};

[Test, TestCaseSource(nameof(generateTriangleColorsTestData))]
public int[] GenerateTriangleColorsTest(int[] halfedges, int expectedCount)
{
var colors = new int[halfedges.Length / 3];
Utilities.GenerateTriangleColors(colors, halfedges, out var count, Allocator.Persistent);
Assert.That(count, Is.EqualTo(expectedCount));
return colors;
}

[Test]
public void GenerateTriangleColorsThrowTest() => Assert.Throws<ArgumentException>(() =>
Utilities.GenerateTriangleColors(colors: new int[1], halfedges: new int[30], out _, Allocator.Persistent)
);
}
}

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