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// This file is part of libigl, a simple c++ geometry processing library.
//
// Copyright (C) 2015 Alec Jacobson <alecjacobson@gmail.com>
//
// This Source Code Form is subject to the terms of the Mozilla Public License
// v. 2.0. If a copy of the MPL was not distributed with this file, You can
// obtain one at http://mozilla.org/MPL/2.0/.
#include "collapse_edge.h"
#include "circulation.h"
#include "edge_collapse_is_valid.h"
#include "decimate_trivial_callbacks.h"
#include <vector>
IGL_INLINE bool igl::collapse_edge(
const int e,
const Eigen::RowVectorXd & p,
Eigen::MatrixXd & V,
Eigen::MatrixXi & F,
Eigen::MatrixXi & E,
Eigen::VectorXi & EMAP,
Eigen::MatrixXi & EF,
Eigen::MatrixXi & EI,
int & e1,
int & e2,
int & f1,
int & f2)
{
std::vector<int> /*Nse,*/Nsf,Nsv;
circulation(e, true,F,EMAP,EF,EI,/*Nse,*/Nsv,Nsf);
std::vector<int> /*Nde,*/Ndf,Ndv;
circulation(e, false,F,EMAP,EF,EI,/*Nde,*/Ndv,Ndf);
return collapse_edge(
e,p,Nsv,Nsf,Ndv,Ndf,V,F,E,EMAP,EF,EI,e1,e2,f1,f2);
}
IGL_INLINE bool igl::collapse_edge(
const int e,
const Eigen::RowVectorXd & p,
/*const*/ std::vector<int> & Nsv,
const std::vector<int> & Nsf,
/*const*/ std::vector<int> & Ndv,
const std::vector<int> & Ndf,
Eigen::MatrixXd & V,
Eigen::MatrixXi & F,
Eigen::MatrixXi & E,
Eigen::VectorXi & EMAP,
Eigen::MatrixXi & EF,
Eigen::MatrixXi & EI,
int & a_e1,
int & a_e2,
int & a_f1,
int & a_f2)
{
// Assign this to 0 rather than, say, -1 so that deleted elements will get
// draw as degenerate elements at vertex 0 (which should always exist and
// never get collapsed to anything else since it is the smallest index)
using namespace Eigen;
using namespace std;
const int eflip = E(e,0)>E(e,1);
// source and destination
const int s = eflip?E(e,1):E(e,0);
const int d = eflip?E(e,0):E(e,1);
if(!edge_collapse_is_valid(Nsv,Ndv))
{
return false;
}
// OVERLOAD: caller may have just computed this
//
// Important to grab neighbors of d before monkeying with edges
const std::vector<int> & nV2Fd = (!eflip ? Nsf : Ndf);
// The following implementation strongly relies on s<d
assert(s<d && "s should be less than d");
// move source and destination to placement
V.row(s) = p;
V.row(d) = p;
// Helper function to replace edge and associate information with NULL
const auto & kill_edge = [&E,&EI,&EF](const int e)
{
E(e,0) = IGL_COLLAPSE_EDGE_NULL;
E(e,1) = IGL_COLLAPSE_EDGE_NULL;
EF(e,0) = IGL_COLLAPSE_EDGE_NULL;
EF(e,1) = IGL_COLLAPSE_EDGE_NULL;
EI(e,0) = IGL_COLLAPSE_EDGE_NULL;
EI(e,1) = IGL_COLLAPSE_EDGE_NULL;
};
// update edge info
// for each flap
const int m = F.rows();
for(int side = 0;side<2;side++)
{
const int f = EF(e,side);
const int v = EI(e,side);
const int sign = (eflip==0?1:-1)*(1-2*side);
// next edge emanating from d
const int e1 = EMAP(f+m*((v+sign*1+3)%3));
// prev edge pointing to s
const int e2 = EMAP(f+m*((v+sign*2+3)%3));
assert(E(e1,0) == d || E(e1,1) == d);
assert(E(e2,0) == s || E(e2,1) == s);
// face adjacent to f on e1, also incident on d
const bool flip1 = EF(e1,1)==f;
const int f1 = flip1 ? EF(e1,0) : EF(e1,1);
assert(f1!=f);
assert(F(f1,0)==d || F(f1,1)==d || F(f1,2) == d);
// across from which vertex of f1 does e1 appear?
const int v1 = flip1 ? EI(e1,0) : EI(e1,1);
// Kill e1
kill_edge(e1);
// Kill f
F(f,0) = IGL_COLLAPSE_EDGE_NULL;
F(f,1) = IGL_COLLAPSE_EDGE_NULL;
F(f,2) = IGL_COLLAPSE_EDGE_NULL;
// map f1's edge on e1 to e2
assert(EMAP(f1+m*v1) == e1);
EMAP(f1+m*v1) = e2;
// side opposite f2, the face adjacent to f on e2, also incident on s
const int opp2 = (EF(e2,0)==f?0:1);
assert(EF(e2,opp2) == f);
EF(e2,opp2) = f1;
EI(e2,opp2) = v1;
// remap e2 from d to s
E(e2,0) = E(e2,0)==d ? s : E(e2,0);
E(e2,1) = E(e2,1)==d ? s : E(e2,1);
if(side==0)
{
a_e1 = e1;
a_f1 = f;
}else
{
a_e2 = e1;
a_f2 = f;
}
}
// finally, reindex faces and edges incident on d. Do this last so asserts
// make sense.
//
// Could actually skip first and last, since those are always the two
// collpased faces. Nah, this is handled by (F(f,v) == d)
//
// Don't attempt to use Nde,Nse here because EMAP has changed
{
int p1 = -1;
for(auto f : nV2Fd)
{
for(int v = 0;v<3;v++)
{
if(F(f,v) == d)
{
const int e1 = EMAP(f+m*((v+1)%3));
const int flip1 = (EF(e1,0)==f)?1:0;
assert( E(e1,flip1) == d || E(e1,flip1) == s);
E(e1,flip1) = s;
const int e2 = EMAP(f+m*((v+2)%3));
// Skip if we just handled this edge (claim: this will be all except
// for the first non-trivial face)
if(e2 != p1)
{
const int flip2 = (EF(e2,0)==f)?0:1;
assert( E(e2,flip2) == d || E(e2,flip2) == s);
E(e2,flip2) = s;
}
F(f,v) = s;
p1 = e1;
break;
}
}
}
}
// Finally, "remove" this edge and its information
kill_edge(e);
return true;
}
IGL_INLINE bool igl::collapse_edge(
const int e,
const Eigen::RowVectorXd & p,
Eigen::MatrixXd & V,
Eigen::MatrixXi & F,
Eigen::MatrixXi & E,
Eigen::VectorXi & EMAP,
Eigen::MatrixXi & EF,
Eigen::MatrixXi & EI)
{
int e1,e2,f1,f2;
return collapse_edge(e,p,V,F,E,EMAP,EF,EI,e1,e2,f1,f2);
}
IGL_INLINE bool igl::collapse_edge(
const decimate_cost_and_placement_callback & cost_and_placement,
Eigen::MatrixXd & V,
Eigen::MatrixXi & F,
Eigen::MatrixXi & E,
Eigen::VectorXi & EMAP,
Eigen::MatrixXi & EF,
Eigen::MatrixXi & EI,
igl::min_heap< std::tuple<double,int,int> > & Q,
Eigen::VectorXi & EQ,
Eigen::MatrixXd & C)
{
int e,e1,e2,f1,f2;
decimate_pre_collapse_callback always_try;
decimate_post_collapse_callback never_care;
decimate_trivial_callbacks(always_try,never_care);
return
collapse_edge(
cost_and_placement,always_try,never_care,
V,F,E,EMAP,EF,EI,Q,EQ,C,e,e1,e2,f1,f2);
}
IGL_INLINE bool igl::collapse_edge(
const decimate_cost_and_placement_callback & cost_and_placement,
const decimate_pre_collapse_callback & pre_collapse,
const decimate_post_collapse_callback & post_collapse,
Eigen::MatrixXd & V,
Eigen::MatrixXi & F,
Eigen::MatrixXi & E,
Eigen::VectorXi & EMAP,
Eigen::MatrixXi & EF,
Eigen::MatrixXi & EI,
igl::min_heap< std::tuple<double,int,int> > & Q,
Eigen::VectorXi & EQ,
Eigen::MatrixXd & C)
{
int e,e1,e2,f1,f2;
return
collapse_edge(
cost_and_placement,pre_collapse,post_collapse,
V,F,E,EMAP,EF,EI,Q,EQ,C,e,e1,e2,f1,f2);
}
IGL_INLINE bool igl::collapse_edge(
const decimate_cost_and_placement_callback & cost_and_placement,
const decimate_pre_collapse_callback & pre_collapse,
const decimate_post_collapse_callback & post_collapse,
Eigen::MatrixXd & V,
Eigen::MatrixXi & F,
Eigen::MatrixXi & E,
Eigen::VectorXi & EMAP,
Eigen::MatrixXi & EF,
Eigen::MatrixXi & EI,
igl::min_heap< std::tuple<double,int,int> > & Q,
Eigen::VectorXi & EQ,
Eigen::MatrixXd & C,
int & e,
int & e1,
int & e2,
int & f1,
int & f2)
{
using namespace Eigen;
using namespace igl;
std::tuple<double,int,int> p;
while(true)
{
// Check if Q is empty
if(Q.empty())
{
// no edges to collapse
e = -1;
return false;
}
// pop from Q
p = Q.top();
if(std::get<0>(p) == std::numeric_limits<double>::infinity())
{
e = -1;
// min cost edge is infinite cost
return false;
}
Q.pop();
e = std::get<1>(p);
// Check if matches timestamp
if(std::get<2>(p) == EQ(e))
{
break;
}
// must be stale or dead.
assert(std::get<2>(p) < EQ(e) || EQ(e) == -1);
// try again.
}
// Why is this computed up here?
// If we just need original face neighbors of edge, could we gather that more
// directly than gathering face neighbors of each vertex?
std::vector<int> /*Nse,*/Nsf,Nsv;
circulation(e, true,F,EMAP,EF,EI,/*Nse,*/Nsv,Nsf);
std::vector<int> /*Nde,*/Ndf,Ndv;
circulation(e, false,F,EMAP,EF,EI,/*Nde,*/Ndv,Ndf);
bool collapsed = true;
if(pre_collapse(V,F,E,EMAP,EF,EI,Q,EQ,C,e))
{
collapsed = collapse_edge(
e,C.row(e),
Nsv,Nsf,Ndv,Ndf,
V,F,E,EMAP,EF,EI,e1,e2,f1,f2);
}else
{
// Aborted by pre collapse callback
collapsed = false;
}
post_collapse(V,F,E,EMAP,EF,EI,Q,EQ,C,e,e1,e2,f1,f2,collapsed);
if(collapsed)
{
// Erase the two, other collapsed edges by marking their timestamps as -1
EQ(e1) = -1;
EQ(e2) = -1;
// TODO: visits edges multiple times, ~150% more updates than should
//
// update local neighbors
// loop over original face neighbors
//
// Can't use previous computed Nse and Nde because those refer to EMAP
// before it was changed...
std::vector<int> Nf;
Nf.reserve( Nsf.size() + Ndf.size() ); // preallocate memory
Nf.insert( Nf.end(), Nsf.begin(), Nsf.end() );
Nf.insert( Nf.end(), Ndf.begin(), Ndf.end() );
// https://stackoverflow.com/a/1041939/148668
std::sort( Nf.begin(), Nf.end() );
Nf.erase( std::unique( Nf.begin(), Nf.end() ), Nf.end() );
// Collect all edges that must be updated
std::vector<int> Ne;
Ne.reserve(3*Nf.size());
for(auto & n : Nf)
{
if(F(n,0) != IGL_COLLAPSE_EDGE_NULL ||
F(n,1) != IGL_COLLAPSE_EDGE_NULL ||
F(n,2) != IGL_COLLAPSE_EDGE_NULL)
{
for(int v = 0;v<3;v++)
{
// get edge id
const int ei = EMAP(v*F.rows()+n);
Ne.push_back(ei);
}
}
}
// Only process edge once
std::sort( Ne.begin(), Ne.end() );
Ne.erase( std::unique( Ne.begin(), Ne.end() ), Ne.end() );
for(auto & ei : Ne)
{
// compute cost and potential placement
double cost;
RowVectorXd place;
cost_and_placement(ei,V,F,E,EMAP,EF,EI,cost,place);
// Increment timestamp
EQ(ei)++;
// Replace in queue
Q.emplace(cost,ei,EQ(ei));
C.row(ei) = place;
}
}else
{
// reinsert with infinite weight (the provided cost function must **not**
// have given this un-collapsable edge inf cost already)
// Increment timestamp
EQ(e)++;
// Replace in queue
Q.emplace(std::numeric_limits<double>::infinity(),e,EQ(e));
}
return collapsed;
}