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|
// ///////////////////////////////////////////
//
// Mesh Simplification Tutorial
//
// (C) by Sven Forstmann in 2014
//
// License : MIT
// http://opensource.org/licenses/MIT
//
// https://github.com/sp4cerat/Fast-Quadric-Mesh-Simplification
//
// 5/2016: Chris Rorden created minimal version for OSX/Linux/Windows compile
// https://github.com/sp4cerat/Fast-Quadric-Mesh-Simplification/
//
// libslic3r refactor by tamasmeszaros
#ifndef SIMPLIFYMESHIMPL_HPP
#define SIMPLIFYMESHIMPL_HPP
#include <vector>
#include <array>
#include <type_traits>
#include <algorithm>
#include <cmath>
#ifndef NDEBUG
#include <ostream>
#include <iostream>
#endif
namespace SimplifyMesh {
using Bary = std::array<double, 3>;
using Index3 = std::array<size_t, 3>;
template<class Vertex> struct vertex_traits {
using coord_type = typename Vertex::coord_type;
using compute_type = coord_type;
static coord_type x(const Vertex &v);
static coord_type& x(Vertex &v);
static coord_type y(const Vertex &v);
static coord_type& y(Vertex &v);
static coord_type z(const Vertex &v);
static coord_type& z(Vertex &v);
};
template<class Mesh> struct mesh_traits {
using vertex_t = typename Mesh::vertex_t;
static size_t face_count(const Mesh &m);
static size_t vertex_count(const Mesh &m);
static vertex_t vertex(const Mesh &m, size_t vertex_idx);
static void vertex(Mesh &m, size_t vertex_idx, const vertex_t &v);
static Index3 triangle(const Mesh &m, size_t face_idx);
static void triangle(Mesh &m, size_t face_idx, const Index3 &t);
static void update(Mesh &m, size_t vertex_count, size_t face_count);
};
namespace implementation {
// A shorter C++14 style form of the enable_if metafunction
template<bool B, class T>
using enable_if_t = typename std::enable_if<B, T>::type;
// Meta predicates for floating, integer and generic arithmetic types
template<class T, class O = T>
using FloatingOnly = enable_if_t<std::is_floating_point<T>::value, O>;
template<class T, class O = T>
using IntegerOnly = enable_if_t<std::is_integral<T>::value, O>;
template<class T, class O = T>
using ArithmeticOnly = enable_if_t<std::is_arithmetic<T>::value, O>;
template< class T >
struct remove_cvref {
using type = typename std::remove_cv<
typename std::remove_reference<T>::type>::type;
};
template< class T >
using remove_cvref_t = typename remove_cvref<T>::type;
template<class T> FloatingOnly<T, bool> is_approx(T val, T ref) { return std::abs(val - ref) < 1e-8; }
template<class T> IntegerOnly <T, bool> is_approx(T val, T ref) { val == ref; }
template<class T> class SymetricMatrix {
static const constexpr size_t N = 10;
public:
explicit SymetricMatrix(ArithmeticOnly<T> c = T()) { std::fill(m, m + N, c); }
// Make plane
SymetricMatrix(T a, T b, T c, T d)
{
m[0] = a * a; m[1] = a * b; m[2] = a * c; m[3] = a * d;
m[4] = b * b; m[5] = b * c; m[6] = b * d;
m[7] = c * c; m[8] = c * d;
m[9] = d * d;
}
T operator[](int c) const { return m[c]; }
// Determinant
T det(int a11, int a12, int a13,
int a21, int a22, int a23,
int a31, int a32, int a33)
{
T det = m[a11] * m[a22] * m[a33] + m[a13] * m[a21] * m[a32] +
m[a12] * m[a23] * m[a31] - m[a13] * m[a22] * m[a31] -
m[a11] * m[a23] * m[a32] - m[a12] * m[a21] * m[a33];
return det;
}
const SymetricMatrix& operator+=(const SymetricMatrix& n)
{
for (size_t i = 0; i < N; ++i) m[i] += n[i];
return *this;
}
SymetricMatrix operator+(const SymetricMatrix& n)
{
SymetricMatrix self = *this;
return self += n;
}
T m[N];
};
template<class V> using TCoord = typename vertex_traits<remove_cvref_t<V>>::coord_type;
template<class V> using TCompute = typename vertex_traits<remove_cvref_t<V>>::compute_type;
template<class V> inline TCoord<V> x(const V &v) { return vertex_traits<remove_cvref_t<V>>::x(v); }
template<class V> inline TCoord<V> y(const V &v) { return vertex_traits<remove_cvref_t<V>>::y(v); }
template<class V> inline TCoord<V> z(const V &v) { return vertex_traits<remove_cvref_t<V>>::z(v); }
template<class V> inline TCoord<V>& x(V &v) { return vertex_traits<remove_cvref_t<V>>::x(v); }
template<class V> inline TCoord<V>& y(V &v) { return vertex_traits<remove_cvref_t<V>>::y(v); }
template<class V> inline TCoord<V>& z(V &v) { return vertex_traits<remove_cvref_t<V>>::z(v); }
template<class M> using TVertex = typename mesh_traits<remove_cvref_t<M>>::vertex_t;
template<class Mesh> using TMeshCoord = TCoord<TVertex<Mesh>>;
template<class Vertex> TCompute<Vertex> dot(const Vertex &v1, const Vertex &v2)
{
return TCompute<Vertex>(x(v1)) * x(v2) +
TCompute<Vertex>(y(v1)) * y(v2) +
TCompute<Vertex>(z(v1)) * z(v2);
}
template<class Vertex> Vertex cross(const Vertex &a, const Vertex &b)
{
return Vertex{y(a) * z(b) - z(a) * y(b),
z(a) * x(b) - x(a) * z(b),
x(a) * y(b) - y(a) * x(b)};
}
template<class Vertex> TCompute<Vertex> lengthsq(const Vertex &v)
{
return TCompute<Vertex>(x(v)) * x(v) + TCompute<Vertex>(y(v)) * y(v) +
TCompute<Vertex>(z(v)) * z(v);
}
template<class Vertex> void normalize(Vertex &v)
{
double square = std::sqrt(lengthsq(v));
x(v) /= square; y(v) /= square; z(v) /= square;
}
using Bary = std::array<double, 3>;
template<class Vertex>
Bary barycentric(const Vertex &p, const Vertex &a, const Vertex &b, const Vertex &c)
{
Vertex v0 = (b - a);
Vertex v1 = (c - a);
Vertex v2 = (p - a);
double d00 = dot(v0, v0);
double d01 = dot(v0, v1);
double d11 = dot(v1, v1);
double d20 = dot(v2, v0);
double d21 = dot(v2, v1);
double denom = d00 * d11 - d01 * d01;
double v = (d11 * d20 - d01 * d21) / denom;
double w = (d00 * d21 - d01 * d20) / denom;
double u = 1.0 - v - w;
return {u, v, w};
}
template<class Mesh> class SimplifiableMesh {
Mesh *m_mesh;
using Vertex = TVertex<Mesh>;
using Coord = TMeshCoord<Mesh>;
using HiPrecison = TCompute<TVertex<Mesh>>;
using SymMat = SymetricMatrix<HiPrecison>;
struct FaceInfo {
size_t idx;
double err[4] = {0.};
bool deleted = false, dirty = false;
Vertex n;
explicit FaceInfo(size_t id): idx(id) {}
};
struct VertexInfo {
size_t idx;
size_t tstart = 0, tcount = 0;
bool border = false;
SymMat q;
explicit VertexInfo(size_t id): idx(id) {}
};
struct Ref { size_t face; size_t vertex; };
std::vector<Ref> m_refs;
std::vector<FaceInfo> m_faceinfo;
std::vector<VertexInfo> m_vertexinfo;
void compact_faces();
void compact();
size_t mesh_vcount() const { return mesh_traits<Mesh>::vertex_count(*m_mesh); }
size_t mesh_facecount() const { return mesh_traits<Mesh>::face_count(*m_mesh); }
size_t vcount() const { return m_vertexinfo.size(); }
inline Vertex read_vertex(size_t vi) const
{
return mesh_traits<Mesh>::vertex(*m_mesh, vi);
}
inline Vertex read_vertex(const VertexInfo &vinf) const
{
return read_vertex(vinf.idx);
}
inline void write_vertex(size_t idx, const Vertex &v) const
{
mesh_traits<Mesh>::vertex(*m_mesh, idx, v);
}
inline void write_vertex(const VertexInfo &vinf, const Vertex &v) const
{
write_vertex(vinf.idx, v);
}
inline Index3 read_triangle(size_t fi) const
{
return mesh_traits<Mesh>::triangle(*m_mesh, fi);
}
inline Index3 read_triangle(const FaceInfo &finf) const
{
return read_triangle(finf.idx);
}
inline void write_triangle(size_t idx, const Index3 &t)
{
return mesh_traits<Mesh>::triangle(*m_mesh, idx, t);
}
inline void write_triangle(const FaceInfo &finf, const Index3 &t)
{
return write_triangle(finf.idx, t);
}
inline std::array<Vertex, 3> triangle_vertices(const Index3 &f) const
{
std::array<Vertex, 3> p;
for (size_t i = 0; i < 3; ++i) p[i] = read_vertex(f[i]);
return p;
}
// Error between vertex and Quadric
static double vertex_error(const SymMat &q, const Vertex &v)
{
Coord _x = x(v) , _y = y(v), _z = z(v);
return q[0] * _x * _x + 2 * q[1] * _x * _y + 2 * q[2] * _x * _z +
2 * q[3] * _x + q[4] * _y * _y + 2 * q[5] * _y * _z +
2 * q[6] * _y + q[7] * _z * _z + 2 * q[8] * _z + q[9];
}
// Error for one edge
double calculate_error(size_t id_v1, size_t id_v2, Vertex &p_result);
void calculate_error(FaceInfo &fi)
{
Vertex p;
Index3 t = read_triangle(fi);
for (size_t j = 0; j < 3; ++j)
fi.err[j] = calculate_error(t[j], t[(j + 1) % 3], p);
fi.err[3] = std::min(fi.err[0], std::min(fi.err[1], fi.err[2]));
}
void update_mesh(int iteration);
// Update triangle connections and edge error after a edge is collapsed
void update_triangles(size_t i, VertexInfo &vi, std::vector<bool> &deleted, int &deleted_triangles);
// Check if a triangle flips when this edge is removed
bool flipped(const Vertex &p, size_t i0, size_t i1, VertexInfo &v0, VertexInfo &v1, std::vector<bool> &deleted);
public:
explicit SimplifiableMesh(Mesh *m) : m_mesh{m}
{
static_assert(
std::is_arithmetic<Coord>::value,
"Coordinate type of mesh has to be an arithmetic type!");
m_faceinfo.reserve(mesh_traits<Mesh>::face_count(*m));
m_vertexinfo.reserve(mesh_traits<Mesh>::vertex_count(*m));
for (size_t i = 0; i < mesh_facecount(); ++i) m_faceinfo.emplace_back(i);
for (size_t i = 0; i < mesh_vcount(); ++i) m_vertexinfo.emplace_back(i);
}
template<class ProgressFn> void simplify_mesh_lossless(ProgressFn &&fn);
void simplify_mesh_lossless() { simplify_mesh_lossless([](int){}); }
};
template<class Mesh> void SimplifiableMesh<Mesh>::compact_faces()
{
auto it = std::remove_if(m_faceinfo.begin(), m_faceinfo.end(),
[](const FaceInfo &inf) { return inf.deleted; });
m_faceinfo.erase(it, m_faceinfo.end());
}
template<class M> void SimplifiableMesh<M>::compact()
{
for (auto &vi : m_vertexinfo) vi.tcount = 0;
compact_faces();
for (FaceInfo &fi : m_faceinfo)
for (size_t vidx : read_triangle(fi)) m_vertexinfo[vidx].tcount = 1;
size_t dst = 0;
for (VertexInfo &vi : m_vertexinfo) {
if (vi.tcount) {
vi.tstart = dst;
write_vertex(dst++, read_vertex(vi));
}
}
size_t vertex_count = dst;
dst = 0;
for (const FaceInfo &fi : m_faceinfo) {
Index3 t = read_triangle(fi);
for (size_t &idx : t) idx = m_vertexinfo[idx].tstart;
write_triangle(dst++, t);
}
mesh_traits<M>::update(*m_mesh, vertex_count, m_faceinfo.size());
}
template<class Mesh>
double SimplifiableMesh<Mesh>::calculate_error(size_t id_v1, size_t id_v2, Vertex &p_result)
{
// compute interpolated vertex
SymMat q = m_vertexinfo[id_v1].q + m_vertexinfo[id_v2].q;
bool border = m_vertexinfo[id_v1].border & m_vertexinfo[id_v2].border;
double error = 0;
HiPrecison det = q.det(0, 1, 2, 1, 4, 5, 2, 5, 7);
if (!is_approx(det, HiPrecison(0)) && !border)
{
// q_delta is invertible
x(p_result) = Coord(-1) / det * q.det(1, 2, 3, 4, 5, 6, 5, 7, 8); // vx = A41/det(q_delta)
y(p_result) = Coord( 1) / det * q.det(0, 2, 3, 1, 5, 6, 2, 7, 8); // vy = A42/det(q_delta)
z(p_result) = Coord(-1) / det * q.det(0, 1, 3, 1, 4, 6, 2, 5, 8); // vz = A43/det(q_delta)
error = vertex_error(q, p_result);
} else {
// det = 0 -> try to find best result
Vertex p1 = read_vertex(id_v1);
Vertex p2 = read_vertex(id_v2);
Vertex p3 = (p1 + p2) / 2;
double error1 = vertex_error(q, p1);
double error2 = vertex_error(q, p2);
double error3 = vertex_error(q, p3);
error = std::min(error1, std::min(error2, error3));
if (is_approx(error1, error)) p_result = p1;
if (is_approx(error2, error)) p_result = p2;
if (is_approx(error3, error)) p_result = p3;
}
return error;
}
template<class Mesh> void SimplifiableMesh<Mesh>::update_mesh(int iteration)
{
if (iteration > 0) compact_faces();
assert(mesh_vcount() == m_vertexinfo.size());
//
// Init Quadrics by Plane & Edge Errors
//
// required at the beginning ( iteration == 0 )
// recomputing during the simplification is not required,
// but mostly improves the result for closed meshes
//
if (iteration == 0) {
for (VertexInfo &vinf : m_vertexinfo) vinf.q = SymMat{};
for (FaceInfo &finf : m_faceinfo) {
Index3 t = read_triangle(finf);
std::array<Vertex, 3> p = triangle_vertices(t);
Vertex n = cross(Vertex(p[1] - p[0]), Vertex(p[2] - p[0]));
normalize(n);
finf.n = n;
for (size_t fi : t)
m_vertexinfo[fi].q += SymMat(x(n), y(n), z(n), -dot(n, p[0]));
calculate_error(finf);
}
}
// Init Reference ID list
for (VertexInfo &vi : m_vertexinfo) { vi.tstart = 0; vi.tcount = 0; }
for (FaceInfo &fi : m_faceinfo)
for (size_t vidx : read_triangle(fi))
m_vertexinfo[vidx].tcount++;
size_t tstart = 0;
for (VertexInfo &vi : m_vertexinfo) {
vi.tstart = tstart;
tstart += vi.tcount;
vi.tcount = 0;
}
// Write References
m_refs.resize(m_faceinfo.size() * 3);
for (size_t i = 0; i < m_faceinfo.size(); ++i) {
const FaceInfo &fi = m_faceinfo[i];
Index3 t = read_triangle(fi);
for (size_t j = 0; j < 3; ++j) {
VertexInfo &vi = m_vertexinfo[t[j]];
assert(vi.tstart + vi.tcount < m_refs.size());
Ref &ref = m_refs[vi.tstart + vi.tcount];
ref.face = i;
ref.vertex = j;
vi.tcount++;
}
}
// Identify boundary : vertices[].border=0,1
if (iteration == 0) {
for (VertexInfo &vi: m_vertexinfo) vi.border = false;
std::vector<size_t> vcount, vids;
for (VertexInfo &vi: m_vertexinfo) {
vcount.clear();
vids.clear();
for(size_t j = 0; j < vi.tcount; ++j) {
assert(vi.tstart + j < m_refs.size());
FaceInfo &fi = m_faceinfo[m_refs[vi.tstart + j].face];
Index3 t = read_triangle(fi);
for (size_t fid : t) {
size_t ofs=0;
while (ofs < vcount.size())
{
if (vids[ofs] == fid) break;
ofs++;
}
if (ofs == vcount.size())
{
vcount.emplace_back(1);
vids.emplace_back(fid);
}
else
vcount[ofs]++;
}
}
for (size_t j = 0; j < vcount.size(); ++j)
if(vcount[j] == 1) m_vertexinfo[vids[j]].border = true;
}
}
}
template<class Mesh>
void SimplifiableMesh<Mesh>::update_triangles(size_t i0,
VertexInfo & vi,
std::vector<bool> &deleted,
int &deleted_triangles)
{
Vertex p;
for (size_t k = 0; k < vi.tcount; ++k) {
assert(vi.tstart + k < m_refs.size());
Ref &r = m_refs[vi.tstart + k];
FaceInfo &fi = m_faceinfo[r.face];
if (fi.deleted) continue;
if (deleted[k]) {
fi.deleted = true;
deleted_triangles++;
continue;
}
Index3 t = read_triangle(fi);
t[r.vertex] = i0;
write_triangle(fi, t);
fi.dirty = true;
fi.err[0] = calculate_error(t[0], t[1], p);
fi.err[1] = calculate_error(t[1], t[2], p);
fi.err[2] = calculate_error(t[2], t[0], p);
fi.err[3] = std::min(fi.err[0], std::min(fi.err[1], fi.err[2]));
m_refs.emplace_back(r);
}
}
template<class Mesh>
bool SimplifiableMesh<Mesh>::flipped(const Vertex & p,
size_t /*i0*/,
size_t i1,
VertexInfo & v0,
VertexInfo & /*v1*/,
std::vector<bool> &deleted)
{
for (size_t k = 0; k < v0.tcount; ++k) {
size_t ridx = v0.tstart + k;
assert(ridx < m_refs.size());
FaceInfo &fi = m_faceinfo[m_refs[ridx].face];
if (fi.deleted) continue;
Index3 t = read_triangle(fi);
int s = m_refs[ridx].vertex;
size_t id1 = t[(s+1) % 3];
size_t id2 = t[(s+2) % 3];
if(id1 == i1 || id2 == i1) // delete ?
{
deleted[k] = true;
continue;
}
Vertex d1 = read_vertex(id1) - p;
normalize(d1);
Vertex d2 = read_vertex(id2) - p;
normalize(d2);
if (std::abs(dot(d1, d2)) > 0.999) return true;
Vertex n = cross(d1, d2);
normalize(n);
deleted[k] = false;
if (dot(n, fi.n) < 0.2) return true;
}
return false;
}
template<class Mesh>
template<class Fn> void SimplifiableMesh<Mesh>::simplify_mesh_lossless(Fn &&fn)
{
// init
for (FaceInfo &fi : m_faceinfo) fi.deleted = false;
// main iteration loop
int deleted_triangles=0;
std::vector<bool> deleted0, deleted1;
for (int iteration = 0; iteration < 9999; iteration ++) {
// update mesh constantly
update_mesh(iteration);
// clear dirty flag
for (FaceInfo &fi : m_faceinfo) fi.dirty = false;
//
// All triangles with edges below the threshold will be removed
//
// The following numbers works well for most models.
// If it does not, try to adjust the 3 parameters
//
double threshold = std::numeric_limits<double>::epsilon(); //1.0E-3 EPS; // Really? (tm)
fn(iteration);
for (FaceInfo &fi : m_faceinfo) {
if (fi.err[3] > threshold || fi.deleted || fi.dirty) continue;
for (size_t j = 0; j < 3; ++j) {
if (fi.err[j] > threshold) continue;
Index3 t = read_triangle(fi);
size_t i0 = t[j];
VertexInfo &v0 = m_vertexinfo[i0];
size_t i1 = t[(j + 1) % 3];
VertexInfo &v1 = m_vertexinfo[i1];
// Border check
if(v0.border != v1.border) continue;
// Compute vertex to collapse to
Vertex p;
calculate_error(i0, i1, p);
deleted0.resize(v0.tcount); // normals temporarily
deleted1.resize(v1.tcount); // normals temporarily
// don't remove if flipped
if (flipped(p, i0, i1, v0, v1, deleted0)) continue;
if (flipped(p, i1, i0, v1, v0, deleted1)) continue;
// not flipped, so remove edge
write_vertex(v0, p);
v0.q = v1.q + v0.q;
size_t tstart = m_refs.size();
update_triangles(i0, v0, deleted0, deleted_triangles);
update_triangles(i0, v1, deleted1, deleted_triangles);
assert(m_refs.size() >= tstart);
size_t tcount = m_refs.size() - tstart;
if(tcount <= v0.tcount)
{
// save ram
if (tcount) {
auto from = m_refs.begin() + tstart, to = from + tcount;
std::copy(from, to, m_refs.begin() + v0.tstart);
}
}
else
// append
v0.tstart = tstart;
v0.tcount = tcount;
break;
}
}
if (deleted_triangles <= 0) break;
deleted_triangles = 0;
}
compact();
}
} // namespace implementation
} // namespace SimplifyMesh
#endif // SIMPLIFYMESHIMPL_HPP
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