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/*=========================================================================
Program: Visualization Toolkit
Module: vtkPolygonBuilder.cxx
Copyright (c) Ken Martin, Will Schroeder, Bill Lorensen
All rights reserved.
See Copyright.txt or http://www.kitware.com/Copyright.htm for details.
This software is distributed WITHOUT ANY WARRANTY; without even
the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
PURPOSE. See the above copyright notice for more information.
=========================================================================*/
#include "vtkPolygonBuilder.h"
#include "vtkIdListCollection.h"
VTK_ABI_NAMESPACE_BEGIN
vtkPolygonBuilder::vtkPolygonBuilder() = default;
void vtkPolygonBuilder::InsertTriangle(const vtkIdType* abc)
{
// basic sanity check (see TestPolygonBuilder3)
if (!abc)
{
return;
}
// don't use collapsed triangles - they can give a crash later on
// during the do-while loop in GetPolygons due to the presence of
// naked, unconnected edges (see TestPolygonBuilder2)
if (abc[0] == abc[1] || abc[0] == abc[2] || abc[1] == abc[2])
{
return;
}
vtkIdType key = abc[0] + abc[1] + abc[2];
bool duplicate(false);
TriangleMap::iterator found = this->Tris.find(key);
if (found != Tris.end())
{
Triangles& tris = found->second;
for (Triangles::iterator it = tris.begin(); !duplicate && it != tris.end(); ++it)
{
Triangle& tri = *it;
for (int i = 0; i < 3; ++i)
{
vtkIdType ta = tri[(i + 0) % 3];
vtkIdType tb = tri[(i + 1) % 3];
vtkIdType tc = tri[(i + 2) % 3];
if (abc[0] == ta && abc[1] == tb && abc[2] == tc)
{
duplicate = true;
break;
}
if (abc[2] == ta && abc[1] == tb && abc[0] == tc)
{
duplicate = true;
break;
}
}
}
Triangle my;
my.push_back(abc[0]);
my.push_back(abc[1]);
my.push_back(abc[2]);
tris.push_back(my);
}
else
{
Triangles tris;
Triangle my;
my.push_back(abc[0]);
my.push_back(abc[1]);
my.push_back(abc[2]);
tris.push_back(my);
this->Tris[key] = tris;
}
if (duplicate)
{
// ignoring duplicate triangle
return;
}
// For each triangle edge: the number of instances of each edge are recorded,
// and edges with exactly one instance are stored. Triangle edges are only
// traversed in a counterclockwise direction.
for (int i = 0; i < 3; i++)
{
Edge edge(abc[i], abc[(i + 1) % 3]);
Edge inverseEdge(abc[(i + 1) % 3], abc[i]);
++(this->EdgeCounter[edge]);
if (this->EdgeCounter[inverseEdge] == 0)
{
this->Edges.insert(std::make_pair(edge.first, edge.second));
}
else if (this->EdgeCounter[edge] == 1)
{
std::pair<EdgeMap::iterator, EdgeMap::iterator> range = Edges.equal_range(inverseEdge.first);
EdgeMap::iterator it = range.first;
for (; it != range.second; ++it)
{
if (it->second == inverseEdge.second)
{
Edges.erase(it);
break;
}
}
}
}
}
void vtkPolygonBuilder::GetPolygons(vtkIdListCollection* polys)
{
polys->RemoveAllItems();
// We now have exactly one instance of each outer edge, corresponding to a
// counterclockwise traversal of the polygon
if (this->Edges.size() < 3)
{
return;
}
while (!(this->Edges.empty()))
{
vtkIdList* poly = vtkIdList::New();
EdgeMap::iterator edgeIt = this->Edges.begin();
Edge edge = *(edgeIt);
vtkIdType firstVtx = edge.first;
do
{
poly->InsertNextId(edge.first);
EdgeMap::iterator at = this->Edges.find(edge.second);
// ignore polygon if Edges map not correct - with the fixes for
// ignoring collapsed triangles and ignoring duplicate triangles
// this should not happen anymore, but it does not hurt to be safe.
//
// UPDATE: from a real-world polyhedron case it IS possible to
// get dangling edges. See TestPolygonBuilder5 for details.
if (at == this->Edges.end())
{
Edges.erase(edgeIt); // remove offending edge
poly->Reset(); // empty the list so it does not get added below
break;
}
edge = *(at);
Edges.erase(at);
} while (edge.first != firstVtx);
if (poly->GetNumberOfIds() > 0)
{
polys->AddItem(poly);
}
else
{
poly->Delete(); // don't leak on failure
}
}
this->Reset();
}
void vtkPolygonBuilder::Reset()
{
this->EdgeCounter.clear();
this->Edges.clear();
}
VTK_ABI_NAMESPACE_END
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