ObjMesh * ObjMeshOrientable::GenerateOrientedMesh()
{
ObjMesh * outputObjMesh = new ObjMesh(*objMesh);
for(unsigned int i=0; i < outputObjMesh->getNumGroups(); i++) // over all groups
{
ObjMesh::Group * groupHandle = (ObjMesh::Group*) outputObjMesh->getGroupHandle(i);
for (unsigned int j=0; j < groupHandle->getNumFaces(); j++) // over all faces
{
const ObjMesh::Face * face = groupHandle->getFaceHandle(j);
if (face->getNumVertices() < 3)
{
printf("Warning: encountered a face with fewer than 3 vertices.\n");
continue;
}
HalfEdge edge = edgeAtFace(i, j);
// loop until edge is first edge
unsigned int startPosition = face->getVertex(0).getPositionIndex();
while (edgeStartVertex(edge).getPositionIndex() != startPosition)
edge = edgeNext(edge);
// reverse the face if not correctly oriented
if (edgeEndVertex(edge).getPositionIndex() != face->getVertex(1).getPositionIndex())
groupHandle->reverseFace(j);
}
}
return outputObjMesh;
}
// returns the number of edges flipped
int ObjMeshOrientable::GenerateHalfEdgeDataStructure()
{
std::cout << "Building the half edge data structure..." << std::endl;
// Step 1: iterate over all faces
// for each face, add all the edges onto the list of half-edges
std::cout << "Step 1: Generating the list of half edges..." << std::endl;
typedef std::vector<ObjMesh::Group> SGroup;
int coutCounter = 0;
for(unsigned int i = 0; i < objMesh->getNumGroups(); i++ )
{
const ObjMesh::Group * currentGroup = objMesh->getGroupHandle(i);
std::cout << " Processing obj group '" << currentGroup->getName() << std::endl;
std::cout << " Iterating through group faces..." << std::endl;
for( unsigned int iFace = 0; iFace < currentGroup->getNumFaces(); ++iFace )
{
ObjMesh::Face face = currentGroup->getFace(iFace); // get face whose number is iFace
if (coutCounter < 100)
{
std::cout << face.getNumVertices() ;
coutCounter++;
}
if (coutCounter == 100)
{
cout << "...[and more]";
coutCounter++;
}
unsigned int edgesSoFar = halfEdges_.size();
for ( unsigned int iVertex = 0; iVertex < face.getNumVertices(); ++iVertex )
{
// create a half edge for each edge, store -1 for half-edge adjacent edge for now
// index vertices starting from 0
int nextEdge = edgesSoFar + ((iVertex + 1) % face.getNumVertices());
HalfEdge halfEdge(edgesSoFar + iVertex, face.getVertex(iVertex).getPositionIndex(), face.getVertex((iVertex + 1) % face.getNumVertices()).getPositionIndex(),
iVertex, (iVertex + 1) % face.getNumVertices(), i, iFace, -1, nextEdge);
halfEdges_.push_back(halfEdge);
}
}
std::cout << std::endl;
}
/*
for (unsigned int i=0; i<halfEdges_.size(); i++)
{
cout << "Half edge "<< i << " :" << endl;
cout << " Opposite edge: " << halfEdges_[i].opposite() << endl;
cout << " Next edge: " << halfEdges_[i].next() << endl;
cout << " Group: " << halfEdges_[i].groupID() << endl;
cout << " Face: " << halfEdges_[i].face() << endl;
cout << " Start vertex: " << halfEdges_[i].startVertex() << endl;
cout << " End vertex: " << halfEdges_[i].endVertex() << endl;
cout << " Start vertex (local): " << halfEdges_[i].startV() << endl;
cout << " End vertex (local): " << halfEdges_[i].endV() << endl;
cout << " Is boundary: " << halfEdges_[i].isBoundary() << endl;
}
*/
// Step 2: build correspondence among half-dges
// for each half-edge, search for the opposite half-edge, if it exists
std::cout << "Step 2: Building correspondence among half-edges..." << std::endl;
std::cout << "Boundary edges: ";
// insert all edges into a binary tree
typedef std::multimap<std::pair< unsigned int, unsigned int > , unsigned int> BinaryTree;
BinaryTree edges;
for (unsigned int i=0; i < halfEdges_.size(); i++)
{
int vertex1 = halfEdges_[i].startVertex();
int vertex2 = halfEdges_[i].endVertex();
if (vertex1 == vertex2)
{
std::cout << "Error: encountered a degenerated edge with equal starting and ending vertex." << std::endl;
std::cout << " Group:" << halfEdges_[i].groupID() << " Face #: " << halfEdges_[i].face() << "Vertex ID: " << vertex1 << std::endl;
exit(1);
}
if (vertex1 > vertex2) // swap
{
int buffer = vertex1;
vertex1 = vertex2;
vertex2 = buffer;
}
std::pair<unsigned int, unsigned int> vertices(vertex1,vertex2);
edges.insert(std::make_pair(vertices,i));
}
// retrieve one by one and build correspondence
for (unsigned int i=0; i < halfEdges_.size(); i++)
{
int vertex1 = halfEdges_[i].startVertex();
int vertex2 = halfEdges_[i].endVertex();
if (vertex1 > vertex2) // swap
{
int buffer = vertex1;
vertex1 = vertex2;
vertex2 = buffer;
}
std::pair<unsigned int, unsigned int> vertices(vertex1,vertex2);
// search for the edge
int hits = 0;
int candidates = 0;
BinaryTree::iterator pos;
for (pos = edges.lower_bound(vertices);
pos != edges.upper_bound(vertices);
++pos)
{
candidates++;
// check if we found ourselves
if (pos->second != i)
{ // not ourselves
halfEdges_[i].setOpposite(pos->second);
hits++;
}
}
if (candidates >= 3)
{
std::cout << "Error: encountered an edge that appears in more than two triangles. Geometry is non-manifold. Exiting." << std::endl;
int faceNum = halfEdges_[i].face();
std::cout << " Group:" << halfEdges_[i].groupID() << std::endl << " Face #: " << faceNum << std::endl;
std::cout << " Edge: " << vertex1 << " " << vertex2 << std::endl;
std::cout << " Vertices: " << objMesh->getPosition(vertex1) << " " << objMesh->getPosition(vertex2) << std::endl;
exit(1);
}
if (hits == 0) // boundary edge
{
//std::cout << "B";
std::cout << "B(" << vertex1 << "," << vertex2 << ") ";
boundaryEdges_.push_back(i);
}
}
std::cout << " total: " << boundaryEdges_.size() << std::endl;
/*
for (unsigned int i=0; i<halfEdges_.size(); i++)
{
cout << "Half edge "<< i << " :" << endl;
cout << " Opposite edge: " << halfEdges_[i].opposite() << endl;
cout << " Next edge: " << halfEdges_[i].next() << endl;
cout << " Group: " << halfEdges_[i].groupID() << endl;
cout << " Face: " << halfEdges_[i].face() << endl;
cout << " Start vertex: " << halfEdges_[i].startVertex() << endl;
cout << " End vertex: " << halfEdges_[i].endVertex() << endl;
cout << " Start vertex (local): " << halfEdges_[i].startV() << endl;
cout << " End vertex (local): " << halfEdges_[i].endV() << endl;
cout << " Is boundary: " << halfEdges_[i].isBoundary() << endl;
}
*/
// now, each half-edge knows its mirror edge, but orientations of faces might be inconsistent
// orient all half-edges consistently
std::cout << "Step 3: Attempting to orient the faces coherently..." << std::endl;
// generate marks for all the edges
std::vector<int> marks(halfEdges_.size(), 0);
// initialize queue
std::set<int> queue;
connectedComponents = 0;
int numOrientationFlips = 0;
while(1) // breakable
{
// find the first un-marked edge and queue it
unsigned int unmarkedEdge;
for (unmarkedEdge = 0; unmarkedEdge < halfEdges_.size(); unmarkedEdge++)
{
if (marks[unmarkedEdge] == 0)
break; // found an unmarked edge
}
if (unmarkedEdge == halfEdges_.size()) // no unmarked edge was found
{
break; // out of while; we are done
}
else
{
cout << "Found a new connected component. Seed half-edge is: " << unmarkedEdge << endl;
connectedComponents++;
queue.insert(unmarkedEdge);
while(queue.size() > 0)
{
int edge = *(queue.begin());
queue.erase(queue.begin());
//std::cout << "Retrieved edge from queue: " << edge << " Queue size: " << queue.size() << std::endl;
//cout << "The edge is boundary: " << halfEdges_[edge].isBoundary() << endl;
//std::cout << "Marking all the edges on this face: ";
// first, mark all the edges on this face as visited
int loop = edge;
do
{
marks[loop] = 1;
//std::cout << loop << " ";
loop = halfEdges_[loop].next();
}
while (loop != edge);
//std::cout << std::endl;
// check if edge is consistent with the opposite edge orientation
// careful: edge might be on the boundary
// find a non-boundary edge on the same face (if it exists)
//std::cout << "Seeking for a non-boundary edge on this face...";
loop = edge;
int exitFlag = 0;
while ((halfEdges_[loop].isBoundary()) && (exitFlag == 0))
{
//cout << loop << " ";
loop = halfEdges_[loop].next();
if (loop == edge) // all edges are boundary
exitFlag = 1;
}
if (exitFlag == 1) // all edges are boundary; this is an isolated face
{
cout << "Encountered an isolated face." << endl;
//cout << "none found." << endl;
continue; // no need to queue anything or flip anything, this was an isolated face
// also, this case can only happen during the first iteration of the while loop, which will also be the last one
}
edge = loop; // now, edge is a non-boundary halfedge
//std::cout << "found non-boundary edge: " << edge << std::endl;
//std::cout << "opposite edge is: " << halfEdges_[edge].opposite() << std::endl;
bool orientationFlipNecessary = (marks[halfEdges_[edge].opposite()] == 1) && (halfEdges_[edge].startVertex() == (edgeOpposite(halfEdges_[edge])).startVertex());
//std::cout << "Orientation flip necessary for this face: " << orientationFlipNecessary << std::endl;
if (orientationFlipNecessary)
{
// flip all edges along this face
//cout << "Orientation flip" << endl;
numOrientationFlips++;
loop = edge;
int cache = 0;
do
{
int nextO = halfEdges_[loop].next();
halfEdges_[loop].setNext(cache);
cache = loop;
halfEdges_[loop].flipOrientation(); // flip orientation
loop = nextO;
}
while (loop != edge);
halfEdges_[loop].setNext(cache);
int groupID = halfEdges_[loop].groupID();
int faceID = halfEdges_[loop].face();
ObjMesh::Group * currentGroup = (ObjMesh::Group*) objMesh->getGroupHandle(groupID);
currentGroup->getFace(faceID).printVertices();
currentGroup->reverseFace(faceID);
currentGroup->getFace(faceID).printVertices();
}
// check if new orientation is consistent eveywhere along the face
// if not, surface is not orientable
// at the same time, queue the opposite edges if they are not marked already
loop = edge;
do
{
if (!halfEdges_[loop].isBoundary()) // skip boundary edges
{
// if opposite unmarked, queue the opposite edge
if (marks[halfEdges_[loop].opposite()] == 0)
{
queue.insert(halfEdges_[loop].opposite());
//marks[halfEdges_[loop].opposite()] = 1; // JNB, 2008
//std::cout << "visiting edge: " << loop << " pushing opposite: " << halfEdges_[loop].opposite() << std::endl;
}
else
{
// opposite edge is marked as already visited
// if orientation consistent, do nothing
// if orientation not consistent, surface is not orientable
bool orientationConsistent = (halfEdges_[loop].startVertex() == (edgeOpposite(halfEdges_[loop])).endVertex());
//std::cout << "visiting edge: " << loop << " opposite marked " << std::endl;
if (!orientationConsistent)
{
std::cout << "Error: surface is non-orientable. Offending edge: [" << halfEdges_[loop].startVertex() << "," << halfEdges_[loop].endVertex() << "]" << std::endl;
exit(1);
}
}
}
loop = halfEdges_[loop].next();
}
while (loop != edge);
}
}
} // end of while
printf("Consistent orientation generated. Performed %d orientation flips.\n", numOrientationFlips);
//PrintHalfEdges();
// step 4: for every vertex, find a half-edge emanating out of it
std::cout << "Step 4: For every vertex, caching a half-edge emanating out of it..." << std::endl;
std::cout << " For every face, caching a half-edge on it..." << std::endl;
for (unsigned int i=0; i< objMesh->getNumVertices(); i++)
edgesAtVertices_.push_back(-1); // value of -1 corresponds to no edge (i.e. isolated vertex)
for (unsigned int i=0; i < halfEdges_.size(); i++)
{
//cout << i << " " << halfEdges_[i].startVertex() << " " << halfEdges_[i].endVertex() << endl;
edgesAtVertices_[halfEdges_[i].endVertex()] = i;
}
// if vertex is on the boundary, rotate the edge until it is an incoming boundary edge
// rotate edge until it is either on the boundary, or we come around to the same edge
int numIsolatedVertices = 0;
for (unsigned int i=0; i < objMesh->getNumVertices(); i++)
{
if (isIsolatedVertex(i))
{
numIsolatedVertices++;
continue;
}
HalfEdge * loop = &edgeAtVertex(i);
HalfEdge * start = loop;
do
{
if (loop->isBoundary())
{
// set the edge to the current edge
edgesAtVertices_[i] = loop->position();
break;
}
loop = &edgePrevious(edgeOpposite(*loop));
}
while (*loop != *start);
// if we came around, no need to change edgeAtVertices[i]
}
if (numIsolatedVertices > 0)
printf("Warning: mesh has %d isolated vertices.\n", numIsolatedVertices);
// build the cache for faces, first reset to -1
for (unsigned int i=0; i < objMesh->getNumGroups(); i++)
{
const ObjMesh::Group * currentGroup = objMesh->getGroupHandle(i);
std::vector<int> dataForThisGroup;
dataForThisGroup.clear();
for (unsigned int j=0; j < currentGroup->getNumFaces(); j++)
{
dataForThisGroup.push_back(-1);
}
edgesAtFaces_.push_back(dataForThisGroup);
}
for (unsigned int i=0; i < halfEdges_.size(); i++)
edgesAtFaces_[halfEdges_[i].groupID()][halfEdges_[i].face()] = i;
// sanity check: none of the face entries should be -1
for (unsigned int i=0; i < objMesh->getNumGroups(); i++)
{
const ObjMesh::Group * currentGroup = objMesh->getGroupHandle(i);
for (unsigned int j=0; j < currentGroup->getNumFaces(); j++)
if (edgesAtFaces_[i][j] == -1)
cout << "Warning: face on group " << i << "(" << currentGroup->getName() << "), position " << j << " has no edges." << endl;
}
determineIfSurfaceHasBoundary();
// testing: previous edge capability
/*
cout << "Testing previous edge capability..." << endl;
for (unsigned int i=0; i < halfEdges_.size(); i++)
{
cout << i << ": " << edgePrevious(halfEdges_[i]).position() << endl;
}
// testing: print out associated edges for every vertex
for (unsigned int i=0; i < vertexPositions_.size(); i++)
{
cout << "Halfedge into vertex " << i << ": " << edgeAtVertex(i).position() << endl;
}
// testing: print out associated edges for every face
for (unsigned int i=0; i < groups_.size(); i++)
for (unsigned int j=0; j < groups_[i].getNumFaces(); j++)
{
cout << "Halfedge on face " << i << " " << j << ": " << edgeAtFace(i,j).position() << endl;
}
// testing: loop around every vertex
for (unsigned int i=0; i < vertexPositions_.size(); i++)
{
cout << "Looping around vertex " << i << ":";
int flag = 0;
HalfEdge * start = &edgeAtVertex(i);
HalfEdge * loop = start;
do
{
cout << loop->position() << " ";
if (flag != 0) // boundary edge, exit the loop
{
cout << " B";
break;
}
loop = &loopVertex(*loop,flag);
}
while (loop->position() != start->position());
cout << endl;
}
*/
std::cout << "Half-edge datastructure constructed successfully." << std::endl;
std::cout << "Statistics: " << std::endl;
std::cout << " Half-edges: " << halfEdges_.size() << std::endl;
std::cout << " Boundary half-edges: " << boundaryEdges_.size() << std::endl;
std::cout << " Connected components: " << connectedComponents << std::endl;
return numOrientationFlips;
}