#ifndef toposlice_skip_fig_H
#define toposlice_skip_fig_H

/* Copyright (C) 2024 Jorge Stolfi, UNICAMP */
/* Last edited on 2024-05-24 05:12:05 by stolfi */

#include <bool.h>
#include <epswr.h>
#include <r2.h>

#include <hedge.h>

void toposlice_skip_fig_make(char *name, int32_t phase);
  /* Creates a figure to illustrate the use of {.skip} pointers in the
    {Extract-Polygon} procedure.
    
    Let {F} be the main face, at the center of the figure If {phase} is
    0, draws only one slicing plane, at height {Z0}. The algorithm is
    assumed to be processing plane {Z0}, in the middle of the inner loop
    of {Extract-Polygon}, with {e'} (the arc {e} at the start of the
    outer loop) being the arc on the left side of {F} that crosses {Z0},
    directed upwards. All {.skip} pointers are still set to {.next}.
    Some of them have been followed already; they are painted red and
    the last one leads to an arc that will be labelled {e}.

    If {phase} is 1, assumes the algorithm is still processing the
    slicing plane at {Z0}, and has just finished the inner loop of
    {Extract-Polygon} and executed the statement {e'.skip <-- e}. At
    this point {e} is the edge on the right side of {F} that crosses
    {Z0} upwards. The edges that are bypassed by {.skip} are drawn in
    light red and their {.skip} pointers are omitted.
    
    If {phase} is 2, the algorithm is assumed to be again in the middle
    of the inner loop of {Extract-Polygon}, but now processing a second
    plane {Z1} aboce {Z0}. There will be several vertices of {F} between
    the two planes, on both sides. Arc {e'} will then be the one on the
    left side of {F} that crosses {Z1} upwards. The {.skip} pointers are
    now like they were at the end of the processing of {Z0}. Some of
    them have been traversed and will be drawn in red. Edges of {e} that
    are skipped over by {.skip} are omitted. */

#endif