//--------------------------------------------------------------
public CDIslandLink(CDIsland islandA, CDIsland islandB, float allowedConcavity, float smallIslandBoost, int vertexLimit, bool sampleVertices, bool sampleCenters)
{
IslandA = islandA;
IslandB = islandB;
Aabb aabb = IslandA.Aabb;
aabb.Grow(IslandB.Aabb);
Aabb = aabb;
float aabbExtentLength = aabb.Extent.Length;
Concavity = GetConcavity(vertexLimit, sampleVertices, sampleCenters);
float alpha = allowedConcavity / (10 * aabbExtentLength);
// Other options for alpha that we could evaluate:
//float alpha = 0.03f / aabbExtentLength; // Independent from concavity.
//alpha = 0.001f;
float aspectRatio = GetAspectRatio();
float term1 = Concavity / aabbExtentLength;
float term2 = alpha * aspectRatio;
// This third term is not in the original paper.
// The goal is to encourage the merging of two small islands. Without this factor
// it can happen that there are few large islands and in each step a single triangle
// is merged into a large island. Resulting in approx. O(n) speed.
// It is much faster if small islands merge first to target an O(log n) speed.
float term3 = smallIslandBoost * Math.Max(IslandA.Triangles.Length, IslandB.Triangles.Length);
DecimationCost = term1 + term2 + term3;
}
//--------------------------------------------------------------
#region Creation & Cleanup
//--------------------------------------------------------------
public CDIslandLink(CDIsland islandA, CDIsland islandB, float allowedConcavity, float smallIslandBoost, int vertexLimit, bool sampleVertices, bool sampleCenters)
{
IslandA = islandA;
IslandB = islandB;
Aabb aabb = IslandA.Aabb;
aabb.Grow(IslandB.Aabb);
Aabb = aabb;
float aabbExtentLength = aabb.Extent.Length;
Concavity = GetConcavity(vertexLimit, sampleVertices, sampleCenters);
float alpha = allowedConcavity / (10 * aabbExtentLength);
// Other options for alpha that we could evaluate:
//float alpha = 0.03f / aabbExtentLength; // Independent from concavity.
//alpha = 0.001f;
float aspectRatio = GetAspectRatio();
float term1 = Concavity / aabbExtentLength;
float term2 = alpha * aspectRatio;
// This third term is not in the original paper.
// The goal is to encourage the merging of two small islands. Without this factor
// it can happen that there are few large islands and in each step a single triangle
// is merged into a large island. Resulting in approx. O(n) speed.
// It is much faster if small islands merge first to target an O(log n) speed.
float term3 = smallIslandBoost * Math.Max(IslandA.Triangles.Length, IslandB.Triangles.Length);
DecimationCost = term1 + term2 + term3;
}
private void MergeIslands()
{
List <CDIslandLink> newLinks = new List <CDIslandLink>();
List <CDIslandLink> obsoleteLinks = (EnableMultithreading) ? new List <CDIslandLink>() : null;
while (_links.Count > 0 && !_cancel)
{
lock (_syncRoot)
{
// Find link with lowest decimation cost.
CDIslandLink bestLink = _links[0];
int bestLinkIndex = 0;
for (int i = 0; i < _links.Count; i++)
{
var link = _links[i];
if (link.DecimationCost < bestLink.DecimationCost)
{
bestLink = link;
bestLinkIndex = i;
}
}
// Remove the found link.
_links.RemoveAt(bestLinkIndex);
// Ignore links that have exceeded the concavity limit.
if (bestLink.Concavity > AllowedConcavity)
{
continue;
}
// The created composite shape is now invalid again.
_decomposition = null;
// Remove island B
_islands.Remove(bestLink.IslandB);
// Merge the islands of the best link into island A.
foreach (var triangle in bestLink.IslandB.Triangles)
{
triangle.Island = bestLink.IslandA;
}
bestLink.IslandA.Triangles = bestLink.IslandA.Triangles.Union(bestLink.IslandB.Triangles).ToArray();
bestLink.IslandA.Aabb = bestLink.Aabb;
bestLink.IslandA.Vertices = bestLink.Vertices;
bestLink.IslandA.ConvexHullBuilder = bestLink.ConvexHullBuilder;
// Remove old links where A and B are involved and add new
// links with A.
if (!EnableMultithreading)
{
for (int i = _links.Count - 1; i >= 0; i--)
{
var link = _links[i];
CDIsland otherIsland = null;
if (link.IslandA == bestLink.IslandA || link.IslandA == bestLink.IslandB)
{
otherIsland = link.IslandB;
}
else if (link.IslandB == bestLink.IslandA || link.IslandB == bestLink.IslandB)
{
otherIsland = link.IslandA;
}
// This link does not link to the merged islands.
if (otherIsland == null)
{
continue;
}
// Remove link.
_links.RemoveAt(i);
// If _newLinks already contains a link with otherIsland we are done.
bool linkExists = false;
foreach (var newLink in newLinks)
{
if (newLink.IslandA == otherIsland || newLink.IslandB == otherIsland)
{
linkExists = true;
break;
}
}
if (linkExists)
{
continue;
}
// Create link between otherIsland and bestLink.IslandA.
link = new CDIslandLink(otherIsland, bestLink.IslandA, AllowedConcavity, SmallIslandBoost,
IntermediateVertexLimit, SampleTriangleVertices, SampleTriangleCenters);
newLinks.Add(link);
}
}
else
{
// Experimental multithreading hack.
// Note: When multithreading is enabled the result is non-deterministic
// because the order of the links in the _links list change...
Parallel.ForEach(_links, link =>
{
CDIsland otherIsland = null;
if (link.IslandA == bestLink.IslandA || link.IslandA == bestLink.IslandB)
{
otherIsland = link.IslandB;
}
else if (link.IslandB == bestLink.IslandA || link.IslandB == bestLink.IslandB)
{
otherIsland = link.IslandA;
}
// This link does not link to the merged islands.
if (otherIsland == null)
{
return;
}
// Remove link.
lock (obsoleteLinks)
obsoleteLinks.Add(link);
// If _newLinks already contains a link with otherIsland we are done.
lock (newLinks)
{
foreach (var newLink in newLinks)
{
if (newLink.IslandA == otherIsland || newLink.IslandB == otherIsland)
{
return;
}
}
}
// Create link between otherIsland and bestLink.IslandA.
link = new CDIslandLink(otherIsland, bestLink.IslandA, AllowedConcavity, SmallIslandBoost,
IntermediateVertexLimit, SampleTriangleVertices, SampleTriangleCenters);
// Add link but only if another thread did not add a similar link.
// TODO: Can this happen or can we remove this check.
lock (newLinks)
{
foreach (var newLink in newLinks)
{
if (newLink.IslandA == otherIsland || newLink.IslandB == otherIsland)
{
return;
}
}
newLinks.Add(link);
}
});
foreach (var link in obsoleteLinks)
{
_links.Remove(link);
}
obsoleteLinks.Clear();
}
// Add new links.
_links.AddRange(newLinks);
newLinks.Clear();
OnProgressChanged((_mesh.NumberOfTriangles - _islands.Count) * 100 / _mesh.NumberOfTriangles);
}
}
}
private void CreateDualGraph()
{
var triangles = new List <CDTriangle>();
// Convert to TriangleMesh.
var triangleMesh = _mesh as TriangleMesh;
if (triangleMesh == null)
{
triangleMesh = new TriangleMesh();
triangleMesh.Add(_mesh, false);
triangleMesh.WeldVertices();
}
// Initialize vertex normals.
var normals = new Vector3F[triangleMesh.Vertices.Count]; // Vertex normals.
var neighborCounts = new int[triangleMesh.Vertices.Count]; // Numbers of triangles that touch each vertex.
for (int i = 0; i < triangleMesh.Vertices.Count; i++)
{
normals[i] = Vector3F.Zero;
neighborCounts[i] = 0;
}
// Go through all triangles. Add the normal to normals and increase the neighborCounts
for (int i = 0; i < triangleMesh.NumberOfTriangles; i++)
{
Triangle triangle = triangleMesh.GetTriangle(i);
var normal = triangle.Normal;
for (int j = 0; j < 3; j++)
{
var vertexIndex = triangleMesh.Indices[(i * 3) + j];
normals[vertexIndex] = normals[vertexIndex] + normal;
neighborCounts[vertexIndex] = neighborCounts[vertexIndex] + 1;
}
}
// Create triangles.
for (int i = 0; i < triangleMesh.NumberOfTriangles; i++)
{
Triangle triangle = triangleMesh.GetTriangle(i);
var cdTriangle = new CDTriangle
{
Id = i,
Vertices = new[] { triangle.Vertex0, triangle.Vertex1, triangle.Vertex2 },
Normal = triangle.Normal, // TODO: Special care for degenerate triangles needed?
};
for (int j = 0; j < 3; j++)
{
var vertexIndex = triangleMesh.Indices[(i * 3) + j];
var normalSum = normals[vertexIndex];
var neighborCount = neighborCounts[vertexIndex];
if (neighborCount > 0)
{
var normal = normalSum / neighborCount;
normal.TryNormalize();
cdTriangle.VertexNormals[j] = normal;
}
}
triangles.Add(cdTriangle);
}
// Create an island for each triangle.
_islands = new List <CDIsland>(triangles.Count);
for (int i = 0; i < triangles.Count; i++)
{
var triangle = triangles[i];
var island = new CDIsland();
island.Id = i;
island.Triangles = new[] { triangle };
island.Vertices = triangle.Vertices;
island.Aabb = new Aabb(triangle.Vertices[0], triangle.Vertices[0]);
island.Aabb.Grow(triangle.Vertices[1]);
island.Aabb.Grow(triangle.Vertices[2]);
triangle.Island = island;
_islands.Add(island);
}
// Find connectivity (= add neighbor links).
for (int i = 0; i < triangles.Count; i++)
{
var a = triangles[i];
for (int j = i + 1; j < triangles.Count; j++)
{
var b = triangles[j];
CDTriangle.FindNeighbors(a, b);
}
}
// Create links.
_links = new List <CDIslandLink>();
for (int i = 0; i < _islands.Count; i++)
{
var island = _islands[i];
var triangle = island.Triangles[0];
// Go through all neighbors.
// If there is a neighbor, create a link.
// To avoid two links per triangle, we create the link only if the id of this triangle
// is less than the other island id.
for (int j = 0; j < 3; j++)
{
CDTriangle neighborTriangle = triangle.Neighbors[j];
if (neighborTriangle != null && neighborTriangle.Island.Id > i)
{
var link = new CDIslandLink(island, neighborTriangle.Island, AllowedConcavity, SmallIslandBoost, IntermediateVertexLimit, SampleTriangleVertices, SampleTriangleCenters);
_links.Add(link);
}
}
}
// Now, we have a lot of islands with 1 triangle each.
}
private void CreateDualGraph()
{
var triangles = new List<CDTriangle>();
// Convert to TriangleMesh.
var triangleMesh = _mesh as TriangleMesh;
if (triangleMesh == null)
{
triangleMesh = new TriangleMesh();
triangleMesh.Add(_mesh, false);
triangleMesh.WeldVertices();
}
// Initialize vertex normals.
var normals = new Vector3F[triangleMesh.Vertices.Count]; // Vertex normals.
var neighborCounts = new int[triangleMesh.Vertices.Count]; // Numbers of triangles that touch each vertex.
for (int i = 0; i < triangleMesh.Vertices.Count; i++)
{
normals[i] = Vector3F.Zero;
neighborCounts[i] = 0;
}
// Go through all triangles. Add the normal to normals and increase the neighborCounts
for (int i = 0; i < triangleMesh.NumberOfTriangles; i++)
{
Triangle triangle = triangleMesh.GetTriangle(i);
var normal = triangle.Normal;
for (int j = 0; j < 3; j++)
{
var vertexIndex = triangleMesh.Indices[(i * 3) + j];
normals[vertexIndex] = normals[vertexIndex] + normal;
neighborCounts[vertexIndex] = neighborCounts[vertexIndex] + 1;
}
}
// Create triangles.
for (int i = 0; i < triangleMesh.NumberOfTriangles; i++)
{
Triangle triangle = triangleMesh.GetTriangle(i);
var cdTriangle = new CDTriangle
{
Id = i,
Vertices = new[] { triangle.Vertex0, triangle.Vertex1, triangle.Vertex2 },
Normal = triangle.Normal, // TODO: Special care for degenerate triangles needed?
};
for (int j = 0; j < 3; j++)
{
var vertexIndex = triangleMesh.Indices[(i * 3) + j];
var normalSum = normals[vertexIndex];
var neighborCount = neighborCounts[vertexIndex];
if (neighborCount > 0)
{
var normal = normalSum / neighborCount;
normal.TryNormalize();
cdTriangle.VertexNormals[j] = normal;
}
}
triangles.Add(cdTriangle);
}
// Create an island for each triangle.
_islands = new List<CDIsland>(triangles.Count);
for (int i = 0; i < triangles.Count; i++)
{
var triangle = triangles[i];
var island = new CDIsland();
island.Id = i;
island.Triangles = new[] { triangle };
island.Vertices = triangle.Vertices;
island.Aabb = new Aabb(triangle.Vertices[0], triangle.Vertices[0]);
island.Aabb.Grow(triangle.Vertices[1]);
island.Aabb.Grow(triangle.Vertices[2]);
triangle.Island = island;
_islands.Add(island);
}
// Find connectivity (= add neighbor links).
for (int i = 0; i < triangles.Count; i++)
{
var a = triangles[i];
for (int j = i + 1; j < triangles.Count; j++)
{
var b = triangles[j];
CDTriangle.FindNeighbors(a, b);
}
}
// Create links.
_links = new List<CDIslandLink>();
for (int i = 0; i < _islands.Count; i++)
{
var island = _islands[i];
var triangle = island.Triangles[0];
// Go through all neighbors.
// If there is a neighbor, create a link.
// To avoid two links per triangle, we create the link only if the id of this triangle
// is less than the other island id.
for (int j = 0; j < 3; j++)
{
CDTriangle neighborTriangle = triangle.Neighbors[j];
if (neighborTriangle != null && neighborTriangle.Island.Id > i)
{
var link = new CDIslandLink(island, neighborTriangle.Island, AllowedConcavity, SmallIslandBoost, IntermediateVertexLimit, SampleTriangleVertices, SampleTriangleCenters);
_links.Add(link);
}
}
}
// Now, we have a lot of islands with 1 triangle each.
}