/* Function returns TRUE if the trapezoid lies inside the polygon */
static int
inside_polygon (trap_t *t, segment_t* seg)
{
int rseg = t->rseg;
if (t->state == ST_INVALID)
return 0;
if ((t->lseg <= 0) || (t->rseg <= 0))
return 0;
if (((t->u0 <= 0) && (t->u1 <= 0)) ||
((t->d0 <= 0) && (t->d1 <= 0))) /* triangle */
return (_greater_than(&seg[rseg].v1, &seg[rseg].v0));
return 0;
}
int triangulate_monotone_polygons(
int nvert,
int nmonpoly,
int op[][3])
{
register int i;
point_t ymax, ymin;
int p, vfirst, posmax, posmin, v;
int vcount, processed;
#ifdef DEBUG
for (i = 0; i < nmonpoly; i++)
{
fprintf(stderr, "\n\nPolygon %d: ", i);
vfirst = mchain[mon[i]].vnum;
p = mchain[mon[i]].next;
fprintf (stderr, "%d ", mchain[mon[i]].vnum);
while (mchain[p].vnum != vfirst)
{
fprintf(stderr, "%d ", mchain[p].vnum);
p = mchain[p].next;
}
}
fprintf(stderr, "\n");
#endif
op_idx = 0;
for (i = 0; i < nmonpoly; i++)
{
vcount = 1;
processed = FALSE;
vfirst = mchain[mon[i]].vnum;
ymax = ymin = vert[vfirst].pt;
posmax = posmin = mon[i];
mchain[mon[i]].marked = TRUE;
p = mchain[mon[i]].next;
while ((v = mchain[p].vnum) != vfirst)
{
if (mchain[p].marked)
{
processed = TRUE;
break; /* break from while */
}
else
mchain[p].marked = TRUE;
if (_greater_than(&vert[v].pt, &ymax))
{
ymax = vert[v].pt;
posmax = p;
}
if (_less_than(&vert[v].pt, &ymin))
{
ymin = vert[v].pt;
posmin = p;
}
p = mchain[p].next;
vcount++;
}
if (processed) /* Go to next polygon */
continue;
if (vcount == 3) /* already a triangle */
{
op[op_idx][0] = mchain[p].vnum;
op[op_idx][1] = mchain[mchain[p].next].vnum;
op[op_idx][2] = mchain[mchain[p].prev].vnum;
op_idx++;
}
else /* triangulate the polygon */
{
v = mchain[mchain[posmax].next].vnum;
if (_equal_to(&vert[v].pt, &ymin))
{ /* LHS is a single line */
triangulate_single_polygon(nvert, posmax, TRI_LHS, op);
}
else
triangulate_single_polygon(nvert, posmax, TRI_RHS, op);
}
}
#ifdef DEBUG
for (i = 0; i < op_idx; i++)
fprintf(stderr, "tri #%d: (%d, %d, %d)\n", i, op[i][0], op[i][1],
op[i][2]);
#endif
return op_idx;
}