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https://git.mirrors.martin98.com/https://github.com/prusa3d/PrusaSlicer.git
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SPE-2194: Split Voronoi cells generated by vertexes into two polygons of equal area instead of selecting just one of the edges based on heuristics.
This commit is contained in:
Lukáš Hejl
Lukas Matena
parent
36f64d9dd7
commit
86fadfc08e
@ -40,6 +40,8 @@ template<typename PT> struct PointCellRange
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PointCellRange() = delete;
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explicit PointCellRange(const PT &source_point) : source_point(source_point) {}
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PointCellRange(const PT &source_point, const VD::edge_type *edge_begin, const VD::edge_type *edge_end)
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: source_point(source_point), edge_begin(edge_begin), edge_end(edge_end) {}
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bool is_valid() const { return edge_begin && edge_end && edge_begin != edge_end; }
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};
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@ -415,6 +415,7 @@ static void delete_vertex_deep(const VD::vertex_type &vertex) {
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while (!vertices_to_delete.empty()) {
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const VD::vertex_type &vertex_to_delete = *vertices_to_delete.front();
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assert(vertex_to_delete.color() != VD_ANNOTATION::VERTEX_ON_CONTOUR);
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vertices_to_delete.pop();
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vertex_to_delete.color(VD_ANNOTATION::DELETED);
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@ -429,99 +430,165 @@ static void delete_vertex_deep(const VD::vertex_type &vertex) {
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}
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}
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static inline Vec2d mk_point_vec2d(const VD::vertex_type *point) {
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assert(point != nullptr);
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return {point->x(), point->y()};
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}
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static inline Vec2d mk_vector_vec2d(const VD::edge_type *edge) {
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assert(edge != nullptr);
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return mk_point_vec2d(edge->vertex1()) - mk_point_vec2d(edge->vertex0());
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}
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static inline Vec2d mk_flipped_vector_vec2d(const VD::edge_type *edge) {
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assert(edge != nullptr);
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return mk_point_vec2d(edge->vertex0()) - mk_point_vec2d(edge->vertex1());
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}
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static double edge_length(const VD::edge_type &edge) {
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assert(edge.is_finite());
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return mk_vector_vec2d(&edge).norm();
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}
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// Used in remove_multiple_edges_in_vertices()
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// Returns length of edge with is connected to contour. To this length is include other edges with follows it if they are almost straight (with the
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// tolerance of 15) And also if node between two subsequent edges is connected only to these two edges.
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static inline double calc_total_edge_length(const VD::edge_type &starting_edge)
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// Removes all edges except one in a Voronoi vertex that has more than one Voronoi edge (for example,
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// in concave parts of a polygon). The one edge that is kept is selected arbitrarily.
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static void remove_excess_voronoi_edges(const VD::vertex_type &vertex)
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{
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double total_edge_length = edge_length(starting_edge);
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const VD::edge_type *prev = &starting_edge;
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do {
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if (prev->is_finite() && non_deleted_edge_count(*prev->vertex1()) > 2)
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break;
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bool found_next_edge = false;
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const VD::edge_type *current = prev->next();
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do {
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if (current->color() == VD_ANNOTATION::DELETED)
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continue;
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Vec2d first_line_vec_n = mk_flipped_vector_vec2d(prev).normalized();
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Vec2d second_line_vec_n = mk_vector_vec2d(current).normalized();
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double angle = ::acos(std::clamp(first_line_vec_n.dot(second_line_vec_n), -1.0, 1.0));
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if (Slic3r::cross2(first_line_vec_n, second_line_vec_n) < 0.0)
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angle = 2.0 * (double) PI - angle;
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if (std::abs(angle - PI) >= (PI / 12))
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continue;
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prev = current;
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found_next_edge = true;
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total_edge_length += edge_length(*current);
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break;
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} while (current = current->prev()->twin(), current != prev->next());
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if (!found_next_edge)
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break;
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} while (prev != &starting_edge);
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return total_edge_length;
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}
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// When a Voronoi vertex has more than one Voronoi edge (for example, in concave parts of a polygon),
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// we leave just one Voronoi edge in the Voronoi vertex.
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// This Voronoi edge is selected based on a heuristic.
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static void remove_multiple_edges_in_vertex(const VD::vertex_type &vertex) {
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if (non_deleted_edge_count(vertex) <= 1)
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if (non_deleted_edge_count(vertex) <= 1) {
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return;
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}
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std::vector<std::pair<const VD::edge_type *, double>> edges_to_check;
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const VD::edge_type *edge = vertex.incident_edge();
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std::vector<const VD::edge_type *> vertex_edges;
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const VD::edge_type *edge = vertex.incident_edge();
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do {
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if (edge->color() == VD_ANNOTATION::DELETED)
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if (edge->color() == VD_ANNOTATION::DELETED) {
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continue;
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}
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edges_to_check.emplace_back(edge, calc_total_edge_length(*edge));
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vertex_edges.emplace_back(edge);
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} while (edge = edge->prev()->twin(), edge != vertex.incident_edge());
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std::sort(edges_to_check.begin(), edges_to_check.end(), [](const auto &l, const auto &r) -> bool {
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return l.second > r.second;
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});
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while (edges_to_check.size() > 1) {
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const VD::edge_type &edge_to_check = *edges_to_check.back().first;
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while (vertex_edges.size() > 1) {
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const VD::edge_type &edge_to_check = *vertex_edges.back();
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edge_to_check.color(VD_ANNOTATION::DELETED);
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edge_to_check.twin()->color(VD_ANNOTATION::DELETED);
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if (const VD::vertex_type &vertex_to_delete = *edge_to_check.vertex1(); can_vertex_be_deleted(vertex_to_delete))
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if (const VD::vertex_type &vertex_to_delete = *edge_to_check.vertex1(); can_vertex_be_deleted(vertex_to_delete)) {
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delete_vertex_deep(vertex_to_delete);
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}
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edges_to_check.pop_back();
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vertex_edges.pop_back();
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}
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}
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// Returns first non-deleted edge in clockwise.
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static const VD::edge_type *get_cw_first_non_deleted_edge(const VD::edge_type *edge_begin)
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{
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const VD::edge_type *edge = edge_begin;
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do {
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if (edge->color() == VD_ANNOTATION::DELETED) {
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continue;
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} else {
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assert(edge->color() != VD_ANNOTATION::VERTEX_ON_CONTOUR);
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return edge;
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}
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} while (edge = edge->prev()->twin(), edge != edge_begin);
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return nullptr;
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}
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// Return convex Polygon for Voronoi cell (Voronoi cell is always convex).
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// During processing a Voronoi cell, it marks its edges as deleted.
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template<typename CellRange>
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static typename std::enable_if<
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std::is_same<CellRange, Geometry::SegmentCellRange<Point>>::value || std::is_same<CellRange, Geometry::PointCellRange<Point>>::value,
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std::optional<Polygon>>::type
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cell_range_to_polygon(const CellRange &cell_range)
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{
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assert(cell_range.is_valid());
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assert(cell_range.edge_begin->vertex0()->color() == VD_ANNOTATION::VERTEX_ON_CONTOUR);
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if (!cell_range.is_valid() || cell_range.edge_begin->vertex0()->color() != VD_ANNOTATION::VERTEX_ON_CONTOUR) {
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return std::nullopt;
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}
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Polygon cell_polygon;
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cell_polygon.points.emplace_back(Geometry::VoronoiUtils::to_point(cell_range.edge_begin->vertex0()).template cast<coord_t>());
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// We have ensured that each cell_polygon have to start at edge_begin->vertex0() and end at edge_end->vertex1().
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const VD::edge_type *edge = cell_range.edge_begin;
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do {
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if (edge->color() == VD_ANNOTATION::DELETED) {
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continue;
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}
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const VD::vertex_type &next_vertex = *edge->vertex1();
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cell_polygon.points.emplace_back(Geometry::VoronoiUtils::to_point(next_vertex).cast<coord_t>());
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edge->color(VD_ANNOTATION::DELETED);
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if (next_vertex.color() == VD_ANNOTATION::VERTEX_ON_CONTOUR || next_vertex.color() == VD_ANNOTATION::DELETED) {
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break;
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}
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edge = edge->twin();
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} while (edge = edge->twin()->next(), edge != cell_range.edge_begin);
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if (edge->vertex1() != cell_range.edge_end->vertex1()) {
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return std::nullopt;
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}
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if (cell_range.edge_begin->vertex0() == cell_range.edge_end->vertex1()) {
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cell_polygon.points.pop_back();
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}
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return cell_polygon;
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}
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static std::optional<Polygon> segment_cell_range_to_polygon(const Geometry::SegmentCellRange<Point> &cell_range)
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{
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return cell_range_to_polygon(cell_range);
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}
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static std::optional<Polygon> point_cell_range_to_polygon(const Geometry::PointCellRange<Point> &cell_range)
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{
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return cell_range_to_polygon(cell_range);
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}
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inline double calc_triangle_area(const Point &a_pt, const Point &b_pt, const Point &c_pt)
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{
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Vec2d ba = (b_pt - a_pt).cast<double>();
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Vec2d ca = (c_pt - a_pt).cast<double>();
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return Slic3r::cross2(ba, ca) / 2.;
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}
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static std::pair<Polygon, Polygon> split_convex_polygon_to_two_polygons_with_equal_area(const Polygon &input_polygon)
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{
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assert(input_polygon.size() >= 3);
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const double half_area = input_polygon.area() / 2.;
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assert(half_area > 0.);
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if (half_area <= 0.) {
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return {};
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}
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Polygon left_polygon;
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left_polygon.points.emplace_back(input_polygon.points[0]);
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Polygon right_polygon;
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right_polygon.points.emplace_back(input_polygon.points[0]);
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right_polygon.points.emplace_back(input_polygon.points[1]);
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double right_polygon_area = 0.;
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size_t curr_idx = 2;
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for (; curr_idx < input_polygon.size(); ++curr_idx) {
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const Point &start_pt = input_polygon.points[0];
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const Point &prev_pt = input_polygon.points[curr_idx - 1];
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const Point &curr_pt = input_polygon.points[curr_idx];
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const double curr_triangle_area = calc_triangle_area(start_pt, prev_pt, curr_pt);
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if ((right_polygon_area + curr_triangle_area) <= half_area) {
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right_polygon_area += curr_triangle_area;
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right_polygon.points.emplace_back(curr_pt);
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} else {
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// Split current triangle.
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const double remaining_area = half_area - right_polygon_area;
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const double split_ratio = remaining_area / curr_triangle_area;
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const Point intersection_pt = prev_pt + (split_ratio * (curr_pt - prev_pt).cast<double>()).cast<coord_t>();
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right_polygon.points.emplace_back(intersection_pt);
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left_polygon.points.emplace_back(intersection_pt);
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break;
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}
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}
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for (; curr_idx < input_polygon.size(); ++curr_idx) {
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left_polygon.points.emplace_back(input_polygon.points[curr_idx]);
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}
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assert(left_polygon.size() >= 3 && right_polygon.size() >= 3);
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return {left_polygon, right_polygon};
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}
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// Returns list of ExPolygons for each extruder + 1 for default unpainted regions.
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// It iterates through all nodes on the border between two different colors, and from this point,
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// start selection always left most edges for every node to construct CCW polygons.
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@ -575,7 +642,7 @@ static std::vector<ExPolygons> extract_colored_segments(const std::vector<Colore
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}
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// Fourth, remove all edges that point outward from the input polygon.
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for (Voronoi::VD::cell_type cell : vd.cells()) {
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for (const Voronoi::VD::cell_type &cell : vd.cells()) {
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if (cell.is_degenerate() || !cell.contains_segment())
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continue;
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@ -597,10 +664,25 @@ static std::vector<ExPolygons> extract_colored_segments(const std::vector<Colore
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}
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}
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// Fifth, if a Voronoi vertex has more than one Voronoi edge, remove all but one of them based on heuristics.
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for (const Voronoi::VD::vertex_type &vertex : vd.vertices()) {
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if (vertex.color() == VD_ANNOTATION::VERTEX_ON_CONTOUR)
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remove_multiple_edges_in_vertex(vertex);
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// Fifth, if a Voronoi vertex has more than one Voronoi edge, remove all except one.
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// Edges are removed only for Voronoi vertices that aren't in the place where color changes.
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for (const Voronoi::VD::cell_type &cell : vd.cells()) {
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if (cell.is_degenerate() || !cell.contains_segment()) {
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continue;
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}
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const ColoredLine &curr_line = Geometry::VoronoiUtils::get_source_segment(cell, colored_lines.begin(), colored_lines.end());
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const ColoredLine &next_line = get_next_contour_line(curr_line);
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if (curr_line.color != next_line.color) {
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continue;
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}
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if (const Geometry::SegmentCellRange<Point> cell_range = Geometry::VoronoiUtils::compute_segment_cell_range(cell, colored_lines.begin(), colored_lines.end());
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cell_range.is_valid()) {
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const VD::vertex_type &vertex = *cell_range.edge_begin->vertex0();
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assert(vertex.color() == VD_ANNOTATION::VERTEX_ON_CONTOUR);
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remove_excess_voronoi_edges(vertex);
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}
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}
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if constexpr (MM_SEGMENTATION_DEBUG_GRAPH) {
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@ -617,38 +699,47 @@ static std::vector<ExPolygons> extract_colored_segments(const std::vector<Colore
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if (cell_range.edge_begin->vertex0()->color() != VD_ANNOTATION::VERTEX_ON_CONTOUR)
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continue;
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const ColoredLine source_segment = Geometry::VoronoiUtils::get_source_segment(cell, colored_lines.begin(), colored_lines.end());
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Polygon segmented_polygon;
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segmented_polygon.points.emplace_back(source_segment.line.b);
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// We have ensured that each segmented_polygon have to start at edge_begin->vertex0() and end at edge_end->vertex1().
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const VD::edge_type *edge = cell_range.edge_begin;
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do {
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if (edge->color() == VD_ANNOTATION::DELETED)
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continue;
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const VD::vertex_type &next_vertex = *edge->vertex1();
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segmented_polygon.points.emplace_back(Geometry::VoronoiUtils::to_point(next_vertex).cast<coord_t>());
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edge->color(VD_ANNOTATION::DELETED);
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if (next_vertex.color() == VD_ANNOTATION::VERTEX_ON_CONTOUR || next_vertex.color() == VD_ANNOTATION::DELETED)
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break;
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edge = edge->twin();
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} while (edge = edge->twin()->next(), edge != cell_range.edge_begin);
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if (edge->vertex1() != cell_range.edge_end->vertex1())
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const ColoredLine &curr_line = Geometry::VoronoiUtils::get_source_segment(cell, colored_lines.begin(), colored_lines.end());
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const std::optional<Polygon> segment_cell_polygon = segment_cell_range_to_polygon(cell_range);
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if (!segment_cell_polygon.has_value())
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continue;
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const Voronoi::VD::vertex_type &cell_begin_vertex = *cell_range.edge_begin->vertex0();
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// The cell_range.edge_begin was deleted, so if any edge is starting in the cell_range.edge_begin->vertex0(),
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// then it is an edge from a cell that was generated by a point, and the cell is between two different colors.
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assert(non_deleted_edge_count(cell_begin_vertex) <= 1);
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if (non_deleted_edge_count(cell_begin_vertex) == 1) {
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const VD::edge_type *point_cell_begin_edge = get_cw_first_non_deleted_edge(cell_range.edge_begin);
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const VD::edge_type *point_cell_end_edge = cell_range.edge_begin->twin();
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assert(point_cell_begin_edge != nullptr && point_cell_end_edge != nullptr);
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if (point_cell_begin_edge == nullptr || point_cell_end_edge == nullptr)
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continue;
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assert(point_cell_begin_edge->color() != VD_ANNOTATION::DELETED && point_cell_end_edge->color() != VD_ANNOTATION::DELETED);
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assert(point_cell_begin_edge->vertex0() == point_cell_end_edge->vertex1());
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const Geometry::PointCellRange<Point> point_cell_range(Geometry::VoronoiUtils::to_point(point_cell_begin_edge->vertex0()).cast<coord_t>(), point_cell_begin_edge, point_cell_end_edge);
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const std::optional<Polygon> point_cell_polygon = point_cell_range_to_polygon(point_cell_range);
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if (!point_cell_polygon.has_value())
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continue;
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const ColoredLine &next_line = get_next_contour_line(curr_line);
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std::pair<Polygon, Polygon> point_cell_polygons = split_convex_polygon_to_two_polygons_with_equal_area(*point_cell_polygon);
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segmented_expolygons_per_extruder[curr_line.color].emplace_back(std::move(point_cell_polygons.first));
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segmented_expolygons_per_extruder[next_line.color].emplace_back(std::move(point_cell_polygons.second));
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}
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cell_range.edge_begin->vertex0()->color(VD_ANNOTATION::DELETED);
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segmented_expolygons_per_extruder[source_segment.color].emplace_back(std::move(segmented_polygon));
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segmented_expolygons_per_extruder[curr_line.color].emplace_back(*segment_cell_polygon);
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}
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}
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// Merge all polygons together for each extruder
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for (auto &segmented_expolygons : segmented_expolygons_per_extruder)
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for (auto &segmented_expolygons : segmented_expolygons_per_extruder) {
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segmented_expolygons = union_ex(segmented_expolygons);
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segmented_expolygons = Slic3r::closing_ex(segmented_expolygons, static_cast<float>(SCALED_EPSILON));
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}
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return segmented_expolygons_per_extruder;
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}
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