Promising approach to medial axis pruning

This commit is contained in:
Alessandro Ranellucci 2014-03-04 23:33:13 +01:00
parent 8644440070
commit 3c77b301a7
13 changed files with 126 additions and 326 deletions

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@ -5,7 +5,7 @@ use warnings;
require Exporter;
our @ISA = qw(Exporter);
our @EXPORT_OK = qw(
PI X Y Z A B X1 Y1 X2 Y2 Z1 Z2 MIN MAX epsilon slope line_atan lines_parallel
PI X Y Z A B X1 Y1 X2 Y2 Z1 Z2 MIN MAX epsilon slope
line_point_belongs_to_segment points_coincide distance_between_points
normalize tan move_points_3D
point_in_polygon point_in_segment segment_in_segment
@ -15,7 +15,7 @@ our @EXPORT_OK = qw(
rotate_points move_points
dot perp polygon_points_visibility
line_intersection bounding_box bounding_box_intersect
angle3points three_points_aligned line_direction
angle3points
chained_path chained_path_from collinear scale unscale
rad2deg_dir bounding_box_center line_intersects_any douglas_peucker
polyline_remove_short_segments normal triangle_normal polygon_is_convex
@ -57,30 +57,6 @@ sub slope {
return ($line->[B][Y] - $line->[A][Y]) / ($line->[B][X] - $line->[A][X]);
}
sub line_atan {
my ($line) = @_;
return atan2($line->[B][Y] - $line->[A][Y], $line->[B][X] - $line->[A][X]);
}
sub line_direction {
my ($line) = @_;
my $atan2 = line_atan($line);
return ($atan2 == PI) ? 0
: ($atan2 < 0) ? ($atan2 + PI)
: $atan2;
}
sub lines_parallel {
my ($line1, $line2) = @_;
return abs(line_direction($line1) - line_direction($line2)) < $parallel_degrees_limit;
}
sub three_points_aligned {
my ($p1, $p2, $p3) = @_;
return lines_parallel([$p1, $p2], [$p2, $p3]);
}
# this subroutine checks whether a given point may belong to a given
# segment given the hypothesis that it belongs to the line containing
# the segment

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@ -224,7 +224,7 @@ sub make_perimeters {
# process thin walls by collapsing slices to single passes
my $min_thin_wall_width = $pwidth/3;
my $min_thin_wall_length = 2*$pwidth;
@thin_walls = @{offset2_ex([ map @$_, @thin_walls ], -0.5*$min_thin_wall_width, +0.5*$min_thin_wall_width)};
#@thin_walls = @{offset2_ex([ map @$_, @thin_walls ], -0.5*$min_thin_wall_width, +0.5*$min_thin_wall_width)};
if (@thin_walls) {
my @p = map @{$_->medial_axis($pspacing)}, @thin_walls;

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@ -7,16 +7,6 @@ use parent 'Slic3r::Polyline';
use Slic3r::Geometry qw(A B X Y);
sub atan {
my $self = shift;
return Slic3r::Geometry::line_atan($self);
}
sub direction {
my $self = shift;
return Slic3r::Geometry::line_direction($self);
}
sub intersection {
my $self = shift;
my ($line, $require_crossing) = @_;

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@ -10,7 +10,7 @@ BEGIN {
}
use Slic3r;
use Slic3r::Geometry qw(line_atan line_direction rad2deg_dir angle3points PI);
use Slic3r::Geometry qw(rad2deg_dir angle3points PI);
#==========================================================
@ -61,3 +61,13 @@ use Slic3r::Geometry qw(line_atan line_direction rad2deg_dir angle3points PI);
}
#==========================================================
sub line_atan {
my ($l) = @_;
return Slic3r::Line->new(@$l)->atan2_;
}
sub line_direction {
my ($l) = @_;
return Slic3r::Line->new(@$l)->direction;
}

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@ -135,10 +135,10 @@ ExPolygon::simplify(double tolerance, ExPolygons &expolygons) const
}
void
ExPolygon::medial_axis(Polylines* polylines) const
ExPolygon::medial_axis(double width, Polylines* polylines) const
{
// init helper object
Slic3r::Geometry::MedialAxis ma;
Slic3r::Geometry::MedialAxis ma(width);
// populate list of segments for the Voronoi diagram
this->contour.lines(&ma.lines);

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@ -26,7 +26,7 @@ class ExPolygon
Polygons simplify_p(double tolerance) const;
ExPolygons simplify(double tolerance) const;
void simplify(double tolerance, ExPolygons &expolygons) const;
void medial_axis(Polylines* polylines) const;
void medial_axis(double width, Polylines* polylines) const;
#ifdef SLIC3RXS
void from_SV(SV* poly_sv);

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@ -3,10 +3,10 @@
#include "PolylineCollection.hpp"
#include "clipper.hpp"
#include <algorithm>
#include <list>
#include <map>
#include <set>
#include <vector>
//#include "voronoi_visual_utils.hpp"
#ifdef SLIC3R_DEBUG
#include "SVG.hpp"
@ -92,6 +92,16 @@ chained_path_items(Points &points, T &items, T &retval)
}
template void chained_path_items(Points &points, ClipperLib::PolyNodes &items, ClipperLib::PolyNodes &retval);
Line
MedialAxis::edge_to_line(const VD::edge_type &edge) {
Line line;
line.a.x = edge.vertex0()->x();
line.a.y = edge.vertex0()->y();
line.b.x = edge.vertex1()->x();
line.b.y = edge.vertex1()->y();
return line;
}
void
MedialAxis::build(Polylines* polylines)
{
@ -104,11 +114,73 @@ MedialAxis::build(Polylines* polylines)
construct_voronoi(this->lines.begin(), this->lines.end(), &this->vd);
// collect valid edges (i.e. prune those not belonging to MAT)
// note: this keeps twins, so it contains twice the number of the valid edges
this->edges.clear();
for (VD::const_edge_iterator edge = this->vd.edges().begin(); edge != this->vd.edges().end(); ++edge) {
if (this->is_valid_edge(*edge)) this->edges.insert(&*edge);
}
// count valid segments for each vertex
std::map< const VD::vertex_type*,std::list<const VD::edge_type*> > vertex_edges;
std::list<const VD::vertex_type*> entry_nodes;
for (VD::const_vertex_iterator vertex = this->vd.vertices().begin(); vertex != this->vd.vertices().end(); ++vertex) {
// get a reference to the list of valid edges originating from this vertex
std::list<const VD::edge_type*>& edges = vertex_edges[&*vertex];
// get one random edge originating from this vertex
const VD::edge_type* edge = vertex->incident_edge();
do {
if (this->edges.count(edge) > 0) // only count valid edges
edges.push_back(edge);
edge = edge->rot_next(); // next edge originating from this vertex
} while (edge != vertex->incident_edge());
// if there's only one edge starting at this vertex then it's a leaf
if (edges.size() == 1) entry_nodes.push_back(&*vertex);
}
// iterate through the leafs to prune short branches
for (std::list<const VD::vertex_type*>::const_iterator vertex = entry_nodes.begin(); vertex != entry_nodes.end(); ++vertex) {
const VD::vertex_type* v = *vertex;
// start a polyline from this vertex
Polyline polyline;
polyline.points.push_back(Point(v->x(), v->y()));
// keep track of visited edges to prevent infinite loops
std::set<const VD::edge_type*> visited_edges;
do {
// get edge starting from v
const VD::edge_type* edge = vertex_edges[v].front();
// if we picked the edge going backwards (thus the twin of the previous edge)
if (visited_edges.count(edge->twin()) > 0) {
edge = vertex_edges[v].back();
}
// avoid getting twice on the same edge
if (visited_edges.count(edge) > 0) break;
visited_edges.insert(edge);
// get ending vertex for this edge and append it to the polyline
v = edge->vertex1();
polyline.points.push_back(Point( v->x(), v->y() ));
// if two edges start at this vertex (one forward one backwards) then
// it's not branching and we can go on
} while (vertex_edges[v].size() == 2);
// if this branch is too short, invalidate all of its edges so that
// they will be ignored when building actual polylines in the loop below
if (polyline.length() < this->width) {
for (std::set<const VD::edge_type*>::const_iterator edge = visited_edges.begin(); edge != visited_edges.end(); ++edge) {
(void)this->edges.erase(*edge);
(void)this->edges.erase((*edge)->twin());
}
}
}
// iterate through the valid edges to build polylines
while (!this->edges.empty()) {
const VD::edge_type& edge = **this->edges.begin();
@ -176,107 +248,26 @@ MedialAxis::is_valid_edge(const VD::edge_type& edge) const
but I don't know how to do it. Maybe we could check the relative angle of
the two segments (we are only interested in facing segments). */
const voronoi_diagram<double>::cell_type &cell1 = *edge.cell();
const voronoi_diagram<double>::cell_type &cell2 = *edge.twin()->cell();
const VD::cell_type &cell1 = *edge.cell();
const VD::cell_type &cell2 = *edge.twin()->cell();
if (cell1.contains_segment() && cell2.contains_segment()) {
Line segment1 = this->retrieve_segment(cell1);
Line segment2 = this->retrieve_segment(cell2);
if (segment1.a == segment2.b || segment1.b == segment2.a) return false;
if (fabs(segment1.atan2_() - segment2.atan2_()) < PI/3) {
//printf("segment1 atan2 = %f, segment2 atan2 = %f\n", segment1.atan2_(), segment2.atan2_());
//printf(" => SAME ATAN2\n");
return false;
}
}
return true;
}
/*
void
MedialAxis::clip_infinite_edge(const voronoi_diagram<double>::edge_type& edge, Points* clipped_edge)
{
const voronoi_diagram<double>::cell_type& cell1 = *edge.cell();
const voronoi_diagram<double>::cell_type& cell2 = *edge.twin()->cell();
Point origin, direction;
// Infinite edges could not be created by two segment sites.
if (cell1.contains_point() && cell2.contains_point()) {
Point p1 = retrieve_point(cell1);
Point p2 = retrieve_point(cell2);
origin.x = (p1.x + p2.x) * 0.5;
origin.y = (p1.y + p2.y) * 0.5;
direction.x = p1.y - p2.y;
direction.y = p2.x - p1.x;
} else {
origin = cell1.contains_segment()
? retrieve_point(cell2)
: retrieve_point(cell1);
Line segment = cell1.contains_segment()
? retrieve_segment(cell1)
: retrieve_segment(cell2);
coord_t dx = high(segment).x - low(segment).x;
coord_t dy = high(segment).y - low(segment).y;
if ((low(segment) == origin) ^ cell1.contains_point()) {
direction.x = dy;
direction.y = -dx;
} else {
direction.x = -dy;
direction.y = dx;
}
}
coord_t side = this->bb.size().x;
coord_t koef = side / (std::max)(fabs(direction.x), fabs(direction.y));
if (edge.vertex0() == NULL) {
clipped_edge->push_back(Point(
origin.x - direction.x * koef,
origin.y - direction.y * koef
));
} else {
clipped_edge->push_back(
Point(edge.vertex0()->x(), edge.vertex0()->y()));
}
if (edge.vertex1() == NULL) {
clipped_edge->push_back(Point(
origin.x + direction.x * koef,
origin.y + direction.y * koef
));
} else {
clipped_edge->push_back(
Point(edge.vertex1()->x(), edge.vertex1()->y()));
}
}
void
MedialAxis::sample_curved_edge(const voronoi_diagram<double>::edge_type& edge, Points* sampled_edge)
{
Point point = edge.cell()->contains_point()
? retrieve_point(*edge.cell())
: retrieve_point(*edge.twin()->cell());
Line segment = edge.cell()->contains_point()
? retrieve_segment(*edge.twin()->cell())
: retrieve_segment(*edge.cell());
double max_dist = 1E-3 * this->bb.size().x;
voronoi_visual_utils<double>::discretize<coord_t,coord_t,Point,Line>(point, segment, max_dist, sampled_edge);
}
*/
Point
MedialAxis::retrieve_point(const voronoi_diagram<double>::cell_type& cell)
{
voronoi_diagram<double>::cell_type::source_index_type index = cell.source_index();
voronoi_diagram<double>::cell_type::source_category_type category = cell.source_category();
if (category == SOURCE_CATEGORY_SINGLE_POINT) {
return this->points[index];
}
index -= this->points.size();
if (category == SOURCE_CATEGORY_SEGMENT_START_POINT) {
return low(this->lines[index]);
} else {
return high(this->lines[index]);
}
}
Line
MedialAxis::retrieve_segment(const voronoi_diagram<double>::cell_type& cell) const
MedialAxis::retrieve_segment(const VD::cell_type& cell) const
{
voronoi_diagram<double>::cell_type::source_index_type index = cell.source_index() - this->points.size();
VD::cell_type::source_index_type index = cell.source_index() - this->points.size();
return this->lines[index];
}

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@ -20,19 +20,18 @@ class MedialAxis {
public:
Points points;
Lines lines;
double width;
MedialAxis(double _width) : width(_width) {};
void build(Polylines* polylines);
void process_edge_neighbors(const voronoi_diagram<double>::edge_type& edge, Points* points);
bool is_valid_edge(const voronoi_diagram<double>::edge_type& edge) const;
//void clip_infinite_edge(const voronoi_diagram<double>::edge_type& edge, Points* clipped_edge);
//void sample_curved_edge(const voronoi_diagram<double>::edge_type& edge, Points* sampled_edge);
Point retrieve_point(const voronoi_diagram<double>::cell_type& cell);
Line retrieve_segment(const voronoi_diagram<double>::cell_type& cell) const;
private:
typedef voronoi_diagram<double> VD;
VD vd;
//BoundingBox bb;
std::set<const VD::edge_type*> edges;
Line edge_to_line(const VD::edge_type &edge);
void process_edge_neighbors(const voronoi_diagram<double>::edge_type& edge, Points* points);
bool is_valid_edge(const voronoi_diagram<double>::edge_type& edge) const;
Line retrieve_segment(const voronoi_diagram<double>::cell_type& cell) const;
};
} }

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@ -1,6 +1,7 @@
#include "Line.hpp"
#include "Polyline.hpp"
#include <algorithm>
#include <cmath>
#include <sstream>
namespace Slic3r {
@ -85,6 +86,21 @@ Line::distance_to(const Point* point) const
return point->distance_to(this);
}
double
Line::atan2_() const
{
return atan2(this->b.y - this->a.y, this->b.x - this->a.x);
}
double
Line::direction() const
{
double atan2 = this->atan2_();
return (atan2 == PI) ? 0
: (atan2 < 0) ? (atan2 + PI)
: atan2;
}
#ifdef SLIC3RXS
void
Line::from_SV(SV* line_sv)

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@ -28,6 +28,8 @@ class Line
Point* point_at(double distance) const;
bool coincides_with(const Line* line) const;
double distance_to(const Point* point) const;
double atan2_() const;
double direction() const;
#ifdef SLIC3RXS
void from_SV(SV* line_sv);

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@ -1,186 +0,0 @@
// Boost.Polygon library voronoi_graphic_utils.hpp header file
// Copyright Andrii Sydorchuk 2010-2012.
// Distributed under the Boost Software License, Version 1.0.
// (See accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt)
// See http://www.boost.org for updates, documentation, and revision history.
#ifndef BOOST_POLYGON_VORONOI_VISUAL_UTILS
#define BOOST_POLYGON_VORONOI_VISUAL_UTILS
#include <stack>
#include <vector>
#include <boost/polygon/isotropy.hpp>
#include <boost/polygon/point_concept.hpp>
#include <boost/polygon/segment_concept.hpp>
#include <boost/polygon/rectangle_concept.hpp>
namespace boost {
namespace polygon {
// Utilities class, that contains set of routines handful for visualization.
template <typename CT>
class voronoi_visual_utils {
public:
// Discretize parabolic Voronoi edge.
// Parabolic Voronoi edges are always formed by one point and one segment
// from the initial input set.
//
// Args:
// point: input point.
// segment: input segment.
// max_dist: maximum discretization distance.
// discretization: point discretization of the given Voronoi edge.
//
// Template arguments:
// InCT: coordinate type of the input geometries (usually integer).
// Point: point type, should model point concept.
// Segment: segment type, should model segment concept.
//
// Important:
// discretization should contain both edge endpoints initially.
template <class InCT1, class InCT2,
class Point,
class Segment>
static
typename enable_if<
typename gtl_and<
typename gtl_if<
typename is_point_concept<
typename geometry_concept< Point >::type
>::type
>::type,
typename gtl_if<
typename is_segment_concept<
typename geometry_concept< Segment >::type
>::type
>::type
>::type,
void
>::type discretize(
const Point& point,
const Segment& segment,
const CT max_dist,
std::vector< Point >* discretization) {
// Apply the linear transformation to move start point of the segment to
// the point with coordinates (0, 0) and the direction of the segment to
// coincide the positive direction of the x-axis.
CT segm_vec_x = cast(x(high(segment))) - cast(x(low(segment)));
CT segm_vec_y = cast(y(high(segment))) - cast(y(low(segment)));
CT sqr_segment_length = segm_vec_x * segm_vec_x + segm_vec_y * segm_vec_y;
// Compute x-coordinates of the endpoints of the edge
// in the transformed space.
CT projection_start = sqr_segment_length *
get_point_projection<InCT1>((*discretization)[0], segment);
CT projection_end = sqr_segment_length *
get_point_projection<InCT1>((*discretization)[1], segment);
// Compute parabola parameters in the transformed space.
// Parabola has next representation:
// f(x) = ((x-rot_x)^2 + rot_y^2) / (2.0*rot_y).
CT point_vec_x = cast(x(point)) - cast(x(low(segment)));
CT point_vec_y = cast(y(point)) - cast(y(low(segment)));
CT rot_x = segm_vec_x * point_vec_x + segm_vec_y * point_vec_y;
CT rot_y = segm_vec_x * point_vec_y - segm_vec_y * point_vec_x;
// Save the last point.
Point last_point = (*discretization)[1];
discretization->pop_back();
// Use stack to avoid recursion.
std::stack<CT> point_stack;
point_stack.push(projection_end);
CT cur_x = projection_start;
CT cur_y = parabola_y(cur_x, rot_x, rot_y);
// Adjust max_dist parameter in the transformed space.
const CT max_dist_transformed = max_dist * max_dist * sqr_segment_length;
while (!point_stack.empty()) {
CT new_x = point_stack.top();
CT new_y = parabola_y(new_x, rot_x, rot_y);
// Compute coordinates of the point of the parabola that is
// furthest from the current line segment.
CT mid_x = (new_y - cur_y) / (new_x - cur_x) * rot_y + rot_x;
CT mid_y = parabola_y(mid_x, rot_x, rot_y);
// Compute maximum distance between the given parabolic arc
// and line segment that discretize it.
CT dist = (new_y - cur_y) * (mid_x - cur_x) -
(new_x - cur_x) * (mid_y - cur_y);
dist = dist * dist / ((new_y - cur_y) * (new_y - cur_y) +
(new_x - cur_x) * (new_x - cur_x));
if (dist <= max_dist_transformed) {
// Distance between parabola and line segment is less than max_dist.
point_stack.pop();
CT inter_x = (segm_vec_x * new_x - segm_vec_y * new_y) /
sqr_segment_length + cast(x(low(segment)));
CT inter_y = (segm_vec_x * new_y + segm_vec_y * new_x) /
sqr_segment_length + cast(y(low(segment)));
discretization->push_back(Point(inter_x, inter_y));
cur_x = new_x;
cur_y = new_y;
} else {
point_stack.push(mid_x);
}
}
// Update last point.
discretization->back() = last_point;
}
private:
// Compute y(x) = ((x - a) * (x - a) + b * b) / (2 * b).
static CT parabola_y(CT x, CT a, CT b) {
return ((x - a) * (x - a) + b * b) / (b + b);
}
// Get normalized length of the distance between:
// 1) point projection onto the segment
// 2) start point of the segment
// Return this length divided by the segment length. This is made to avoid
// sqrt computation during transformation from the initial space to the
// transformed one and vice versa. The assumption is made that projection of
// the point lies between the start-point and endpoint of the segment.
template <class InCT,
class Point,
class Segment>
static
typename enable_if<
typename gtl_and<
typename gtl_if<
typename is_point_concept<
typename geometry_concept< Point >::type
>::type
>::type,
typename gtl_if<
typename is_segment_concept<
typename geometry_concept< Segment >::type
>::type
>::type
>::type,
CT
>::type get_point_projection(
const Point& point, const Segment& segment) {
CT segment_vec_x = cast(x(high(segment))) - cast(x(low(segment)));
CT segment_vec_y = cast(y(high(segment))) - cast(y(low(segment)));
CT point_vec_x = x(point) - cast(x(low(segment)));
CT point_vec_y = y(point) - cast(y(low(segment)));
CT sqr_segment_length =
segment_vec_x * segment_vec_x + segment_vec_y * segment_vec_y;
CT vec_dot = segment_vec_x * point_vec_x + segment_vec_y * point_vec_y;
return vec_dot / sqr_segment_length;
}
template <typename InCT>
static CT cast(const InCT& value) {
return static_cast<CT>(value);
}
};
}
}
#endif // BOOST_POLYGON_VORONOI_VISUAL_UTILS

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@ -26,7 +26,7 @@
ExPolygons simplify(double tolerance);
Polygons simplify_p(double tolerance);
Polylines medial_axis(double width)
%code{% THIS->medial_axis(&RETVAL); %};
%code{% THIS->medial_axis(width, &RETVAL); %};
%{
ExPolygon*

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@ -21,6 +21,8 @@
void scale(double factor);
void translate(double x, double y);
double length();
double atan2_();
double direction();
Point* midpoint()
%code{% const char* CLASS = "Slic3r::Point"; RETVAL = THIS->midpoint(); %};
Point* point_at(double distance)