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refactor: unify build triangles bw
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Unifies methods related to building triangles in Bower-Watson algorithm. Star and Amphitheater topology are now merged into single method with a proper comment.
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@andywiecko
andywiecko committed Nov 22, 2024
1 parent cadad6a commit 332a04a
Showing 1 changed file with 63 additions and 101 deletions.
164 changes: 63 additions & 101 deletions Runtime/Triangulator.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -3163,38 +3163,29 @@ public struct UnsafeBowerWatson
/// </summary>
private int heLoopId;

private int UnsafeInsertPointCommon(T2 p, int initTriangle)
public int UnsafeInsertPointBulk(T2 p, int initTriangle, NativeList<int> heQueue = default, NativeList<int> tQueue = default) => UnsafeInsertPoint(p, initTriangle, initHe: -1, boundary: false, heQueue, tQueue);

public int UnsafeInsertPointBoundary(T2 p, int initHe, NativeList<int> heQueue = default, NativeList<int> tQueue = default) => UnsafeInsertPoint(p, initTriangle: -1, initHe, boundary: true, heQueue, tQueue);

private int UnsafeInsertPoint(T2 p, int initTriangle, int initHe, bool boundary, NativeList<int> heQueue = default, NativeList<int> tQueue = default)
{
var pId = Output.Positions.Length;
Output.Positions.Add(p);
ClearTmpBuffers();
RecalculateBadTriangles(p, initTriangle: boundary ? initHe / 3 : initTriangle);
BuildPolygon(initHe: boundary ? initHe : heLoopId, boundary);
ProcessBadTriangles(heQueue, tQueue);
BuildNewTriangles(pId, boundary);
return PathPoints.Length;
}

private void ClearTmpBuffers()
{
TrianglesQueue.Clear();
PathPoints.Clear();
PathHalfedges.Clear();
VisitedTriangles.Clear();
VisitedTriangles.Length = Output.Triangles.Length / 3;

RecalculateBadTriangles(p, initTriangle);

return pId;
}

public int UnsafeInsertPointBulk(T2 p, int initTriangle, NativeList<int> heQueue = default, NativeList<int> tQueue = default)
{
var pId = UnsafeInsertPointCommon(p, initTriangle);
BuildPolygon(initHe: heLoopId, amphitheater: false);
ProcessBadTriangles(heQueue, tQueue);
BuildNewTrianglesForStar(pId);
return PathPoints.Length;
}

public int UnsafeInsertPointBoundary(T2 p, int initHe, NativeList<int> heQueue = default, NativeList<int> tQueue = default)
{
var pId = UnsafeInsertPointCommon(p, initHe / 3);
BuildPolygon(initHe, amphitheater: true);
ProcessBadTriangles(heQueue, tQueue);
BuildNewTrianglesForAmphitheater(pId);
return PathPoints.Length;
}

private void RecalculateBadTriangles(T2 p, int initTriangle)
Expand Down Expand Up @@ -3238,12 +3229,12 @@ private void RecalculateBadTriangles(T2 p, int initTriangle)
}
}

private void BuildPolygon(int initHe, bool amphitheater)
private void BuildPolygon(int initHe, bool boundary)
{
var triangles = Output.Triangles;
var halfedges = Output.Halfedges;

if (!amphitheater)
if (!boundary)
{
PathPoints.Add(triangles[initHe]);
PathHalfedges.Add(halfedges[initHe]);
Expand All @@ -3269,7 +3260,7 @@ private void BuildPolygon(int initHe, bool amphitheater)
id = he;
}

if (amphitheater)
if (boundary)
{
PathPoints.Add(triangles[initHe]);
PathHalfedges.Add(-1);
Expand Down Expand Up @@ -3349,18 +3340,46 @@ static void AdaptHe(NativeList<int> halfedges, int he, int rId, int wId)
}
}

private void BuildNewTrianglesForStar(int pId)
private void BuildNewTriangles(int pId, bool boundary)
{
// Note: In this method, we create new triangles with the inserted point `pId`.
// There are two possible topologies to consider, depending on whether
// the point is inserted on the boundary or not.
//
// - **Star topology**. The inserted point (pId) lies entirely within the region,
// forming new triangles radiating outward from it. All new triangles share pId
// as a common vertex, resembling a star. Example:
//
// ..................
// ..' :. ....''':
// .''' :...''' :'
// :.......* pId :'
// :. .''.. .:
// :. .' ''.. :
// :.'...........:.'
//
// - **Amphitheater topology**. The inserted point (pId) lies on the boundary,
// creating new triangles that connect to the cavity edges. Example:
//
// ....
// .': ''''''....
// :' : ..:'':
// .: : ...''' ''..
// .:........*...............:.
// pId
//
var triangles = Output.Triangles;
var halfedges = Output.Halfedges;
var constrainedHalfedges = Output.ConstrainedHalfedges;

var createdTrianglesCount = boundary ? PathPoints.Length - 1 : PathPoints.Length;

// Build triangles/circles for inserted point pId.
var initTriangles = triangles.Length;
triangles.Length += 3 * PathPoints.Length;
triangles.Length += 3 * createdTrianglesCount;
if (Circles.IsCreated)
{
Circles.Length += PathPoints.Length;
Circles.Length += createdTrianglesCount;
}
for (int i = 0; i < PathPoints.Length - 1; i++)
{
Expand All @@ -3372,78 +3391,22 @@ private void BuildNewTrianglesForStar(int pId)
Circles[initTriangles / 3 + i] = new(CalculateCircumCircle(pId, PathPoints[i], PathPoints[i + 1], Output.Positions.AsArray()));
}
}
triangles[^3] = pId;
triangles[^2] = PathPoints[^1];
triangles[^1] = PathPoints[0];
if (Circles.IsCreated)
{
Circles[^1] = new(CalculateCircumCircle(pId, PathPoints[^1], PathPoints[0], Output.Positions.AsArray()));
}

// Build half-edges for inserted point pId.
var heOffset = halfedges.Length;
halfedges.Length += 3 * PathPoints.Length;
constrainedHalfedges.Length += 3 * PathPoints.Length;
for (int i = 0; i < PathPoints.Length - 1; i++)
{
var he = PathHalfedges[i];
halfedges[3 * i + 1 + heOffset] = he;
if (he != -1)
{
halfedges[he] = 3 * i + 1 + heOffset;
constrainedHalfedges[3 * i + 1 + heOffset] = constrainedHalfedges[he];
}
else
{
constrainedHalfedges[3 * i + 1 + heOffset] = true;
}
halfedges[3 * i + 2 + heOffset] = 3 * i + 3 + heOffset;
halfedges[3 * i + 3 + heOffset] = 3 * i + 2 + heOffset;
}
var phe = PathHalfedges[^1];
halfedges[heOffset + 3 * (PathPoints.Length - 1) + 1] = phe;
if (phe != -1)
if (!boundary)
{
halfedges[phe] = heOffset + 3 * (PathPoints.Length - 1) + 1;
constrainedHalfedges[heOffset + 3 * (PathPoints.Length - 1) + 1] = constrainedHalfedges[phe];
}
else
{
constrainedHalfedges[heOffset + 3 * (PathPoints.Length - 1) + 1] = true;
}
halfedges[heOffset] = heOffset + 3 * (PathPoints.Length - 1) + 2;
halfedges[heOffset + 3 * (PathPoints.Length - 1) + 2] = heOffset;
}

private void BuildNewTrianglesForAmphitheater(int pId)
{
var triangles = Output.Triangles;
var halfedges = Output.Halfedges;
var constrainedHalfedges = Output.ConstrainedHalfedges;

// Build triangles/circles for inserted point pId.
var initTriangles = triangles.Length;
triangles.Length += 3 * (PathPoints.Length - 1);
if (Circles.IsCreated)
{
Circles.Length += PathPoints.Length - 1;
}
for (int i = 0; i < PathPoints.Length - 1; i++)
{
triangles[initTriangles + 3 * i + 0] = pId;
triangles[initTriangles + 3 * i + 1] = PathPoints[i];
triangles[initTriangles + 3 * i + 2] = PathPoints[i + 1];
triangles[^3] = pId;
triangles[^2] = PathPoints[^1];
triangles[^1] = PathPoints[0];
if (Circles.IsCreated)
{
Circles[initTriangles / 3 + i] = new(CalculateCircumCircle(pId, PathPoints[i], PathPoints[i + 1], Output.Positions.AsArray()));
Circles[^1] = new(CalculateCircumCircle(pId, PathPoints[^1], PathPoints[0], Output.Positions.AsArray()));
}
}

// Build half-edges for inserted point pId.
var heOffset = halfedges.Length;
halfedges.Length += 3 * (PathPoints.Length - 1);
constrainedHalfedges.Length += 3 * (PathPoints.Length - 1);
for (int i = 0; i < PathPoints.Length - 2; i++)
halfedges.Length += 3 * createdTrianglesCount;
constrainedHalfedges.Length += 3 * createdTrianglesCount;
for (int i = 0; i < createdTrianglesCount - 1; i++)
{
var he = PathHalfedges[i];
halfedges[3 * i + 1 + heOffset] = he;
Expand All @@ -3459,20 +3422,19 @@ private void BuildNewTrianglesForAmphitheater(int pId)
halfedges[3 * i + 2 + heOffset] = 3 * i + 3 + heOffset;
halfedges[3 * i + 3 + heOffset] = 3 * i + 2 + heOffset;
}

var phe = PathHalfedges[^2];
halfedges[heOffset + 3 * (PathPoints.Length - 2) + 1] = phe;
var phe = boundary ? PathHalfedges[^2] : PathHalfedges[^1];
halfedges[heOffset + 3 * (createdTrianglesCount - 1) + 1] = phe;
if (phe != -1)
{
halfedges[phe] = heOffset + 3 * (PathPoints.Length - 2) + 1;
constrainedHalfedges[heOffset + 3 * (PathPoints.Length - 2) + 1] = constrainedHalfedges[phe];
halfedges[phe] = heOffset + 3 * (createdTrianglesCount - 1) + 1;
constrainedHalfedges[heOffset + 3 * (createdTrianglesCount - 1) + 1] = constrainedHalfedges[phe];
}
else
{
constrainedHalfedges[heOffset + 3 * (PathPoints.Length - 2) + 1] = true;
constrainedHalfedges[heOffset + 3 * (createdTrianglesCount - 1) + 1] = true;
}
halfedges[heOffset] = -1;
halfedges[heOffset + 3 * (PathPoints.Length - 2) + 2] = -1;
halfedges[heOffset] = boundary ? -1 : heOffset + 3 * (createdTrianglesCount - 1) + 2;
halfedges[heOffset + 3 * (createdTrianglesCount - 1) + 2] = boundary ? -1 : heOffset;
}

private readonly void AdaptQueues(int wId, NativeList<int> heQueue, NativeList<int> tQueue)
Expand Down

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