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ReduceFace now uses an IndexSet for containment. #412

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Merged
RossNordby merged 1 commit into from
Aug 9, 2026
Merged

ReduceFace now uses an IndexSet for containment. #412

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19 changes: 13 additions & 6 deletions BepuPhysics/Collidables/ConvexHullHelper.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -301,7 +301,7 @@ static int FindNextIndexForFaceHull(Vector2 start, Vector2 previousEdgeDirection

}

static void ReduceFace(ref QuickList<int> faceVertexIndices, Vector3 faceNormal, Span<Vector3> points, float planeEpsilon, ref QuickList<Vector2> facePoints, ref Buffer<int> allowVertex, ref QuickList<int> reducedIndices)
static void ReduceFace(ref QuickList<int> faceVertexIndices, Vector3 faceNormal, Span<Vector3> points, float planeEpsilon, ref QuickList<Vector2> facePoints, ref Buffer<int> allowVertex, ref QuickList<int> reducedIndices, ref IndexSet reducedIndicesSet)
{
Debug.Assert(facePoints.Count == 0 && reducedIndices.Count == 0 && facePoints.Span.Length >= faceVertexIndices.Count && reducedIndices.Span.Length >= faceVertexIndices.Count);
for (int i = faceVertexIndices.Count - 1; i >= 0; --i)
Expand Down Expand Up @@ -394,14 +394,16 @@ static void ReduceFace(ref QuickList<int> faceVertexIndices, Vector3 faceNormal,
var greatestDistance = (float)Math.Sqrt(greatestDistanceSquared);
var initialOffsetDirection = (facePoints[initialIndex] - centroid) / greatestDistance;
var previousEdgeDirection = new Vector2(initialOffsetDirection.Y, -initialOffsetDirection.X);
reducedIndicesSet.Clear();
reducedIndicesSet.AddUnsafely(faceVertexIndices[initialIndex]);
reducedIndices.AllocateUnsafely() = faceVertexIndices[initialIndex];

var previousEndIndex = initialIndex;
for (int i = 0; i < facePoints.Count; ++i)
{
var nextIndex = FindNextIndexForFaceHull(facePoints[previousEndIndex], previousEdgeDirection, planeEpsilon, ref facePoints);
//This can return -1 in the event of a completely degenerate face.
if (nextIndex == -1 || reducedIndices.Contains(faceVertexIndices[nextIndex]))
if (nextIndex == -1 || reducedIndicesSet.Contains(faceVertexIndices[nextIndex]))
{
if (nextIndex >= 0)
{
Expand All @@ -413,6 +415,8 @@ static void ReduceFace(ref QuickList<int> faceVertexIndices, Vector3 faceNormal,
Debug.Assert(cycleStartIndex >= 0);
if (cycleStartIndex > 0)
{
for (int j = 0; j < cycleStartIndex; ++j)
reducedIndicesSet.Remove(reducedIndices[j]);
//Note that order matters; can't do a last element swapping remove.
reducedIndices.Span.CopyTo(cycleStartIndex, reducedIndices.Span, 0, reducedIndices.Count - cycleStartIndex);
reducedIndices.Count -= cycleStartIndex;
Expand All @@ -421,6 +425,7 @@ static void ReduceFace(ref QuickList<int> faceVertexIndices, Vector3 faceNormal,
break;
}
reducedIndices.AllocateUnsafely() = faceVertexIndices[nextIndex];
reducedIndicesSet.AddUnsafely(faceVertexIndices[nextIndex]);
previousEdgeDirection = Vector2.Normalize(facePoints[nextIndex] - facePoints[previousEndIndex]);
previousEndIndex = nextIndex;
}
Expand All @@ -429,7 +434,7 @@ static void ReduceFace(ref QuickList<int> faceVertexIndices, Vector3 faceNormal,
for (int i = 0; i < faceVertexIndices.Count; ++i)
{
var index = faceVertexIndices[i];
if (!reducedIndices.Contains(index))
if (!reducedIndicesSet.Contains(index))
{
allowVertex[index] = 0;
}
Expand Down Expand Up @@ -738,9 +743,10 @@ public static void ComputeHull(Span<Vector3> points, BufferPool pool, out HullDa
Debug.Assert(rawFaceVertexIndices.Count >= 2);
var facePoints = new QuickList<Vector2>(points.Length, pool);
var reducedFaceIndices = new QuickList<int>(points.Length, pool);
var reducedIndicesSet = new IndexSet(pool, points.Length);


ReduceFace(ref rawFaceVertexIndices, initialFaceNormal, points, planeSlabEpsilonNarrow, ref facePoints, ref allowVertices, ref reducedFaceIndices);
ReduceFace(ref rawFaceVertexIndices, initialFaceNormal, points, planeSlabEpsilonNarrow, ref facePoints, ref allowVertices, ref reducedFaceIndices, ref reducedIndicesSet);

var faces = new QuickList<EarlyFace>(points.Length, pool);
var edgesToTest = new QuickList<EdgeToTest>(points.Length, pool);
Expand Down Expand Up @@ -806,7 +812,7 @@ public static void ComputeHull(Span<Vector3> points, BufferPool pool, out HullDa
FindExtremeFace(basisXBundle, basisYBundle, basisOrigin, edgeToTest.Endpoints, ref pointBundles, indexOffsetBundle, allowVertices, points.Length, ref projectedOnX, ref projectedOnY, planeSlabEpsilon, ref rawFaceVertexIndices, out var faceNormal);
reducedFaceIndices.Count = 0;
facePoints.Count = 0;
ReduceFace(ref rawFaceVertexIndices, faceNormal, points, planeSlabEpsilonNarrow, ref facePoints, ref allowVertices, ref reducedFaceIndices);
ReduceFace(ref rawFaceVertexIndices, faceNormal, points, planeSlabEpsilonNarrow, ref facePoints, ref allowVertices, ref reducedFaceIndices, ref reducedIndicesSet);

if (reducedFaceIndices.Count < 3)
{
Expand Down Expand Up @@ -852,7 +858,7 @@ public static void ComputeHull(Span<Vector3> points, BufferPool pool, out HullDa
face.VertexIndices.Count = 0;
facePoints.Count = 0;
face.VertexIndices.EnsureCapacity(rawFaceVertexIndices.Count, pool);
ReduceFace(ref rawFaceVertexIndices, faceNormal, points, planeSlabEpsilonNarrow, ref facePoints, ref allowVertices, ref face.VertexIndices);
ReduceFace(ref rawFaceVertexIndices, faceNormal, points, planeSlabEpsilonNarrow, ref facePoints, ref allowVertices, ref face.VertexIndices, ref reducedIndicesSet);
#if DEBUG_STEPS
step.UpdateForFaceMerge(rawFaceVertexIndices, face.VertexIndices, allowVertices, i);
#endif
Expand Down Expand Up @@ -933,6 +939,7 @@ public static void ComputeHull(Span<Vector3> points, BufferPool pool, out HullDa
edgesToTest.Dispose(pool);
facePoints.Dispose(pool);
reducedFaceIndices.Dispose(pool);
reducedIndicesSet.Dispose(pool);
rawFaceVertexIndices.Dispose(pool);
pool.Return(ref allowVertices);
pool.Return(ref projectedOnX);
Expand Down
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