static int
monotonate_trapezoids(int nsegs, segment_t*seg, trap_t* tr,
int flip, boxf* decomp)
{
int i, size;
int tr_start;
int tr_size = TRSIZE(nsegs);
int* visited = N_NEW(tr_size,int);
mchain = N_NEW(tr_size, monchain_t);
vert = N_NEW(nsegs+1,vertexchain_t);
mon = N_NEW(nsegs, int);
/* First locate a trapezoid which lies inside the polygon */
/* and which is triangular */
for (i = 0; i < TRSIZE(nsegs); i++)
if (inside_polygon(&tr[i], seg)) break;
tr_start = i;
/* Initialise the mon data-structure and start spanning all the */
/* trapezoids within the polygon */
for (i = 1; i <= nsegs; i++) {
mchain[i].prev = seg[i].prev;
mchain[i].next = seg[i].next;
mchain[i].vnum = i;
vert[i].pt = seg[i].v0;
vert[i].vnext[0] = seg[i].next; /* next vertex */
vert[i].vpos[0] = i; /* locn. of next vertex */
vert[i].nextfree = 1;
}
chain_idx = nsegs;
mon_idx = 0;
mon[0] = 1; /* position of any vertex in the first */
/* chain */
/* traverse the polygon */
if (tr[tr_start].u0 > 0)
size = traverse_polygon (visited, decomp, 0, seg, tr, 0, tr_start, tr[tr_start].u0, flip, TR_FROM_UP);
else if (tr[tr_start].d0 > 0)
size = traverse_polygon (visited, decomp, 0, seg, tr, 0, tr_start, tr[tr_start].d0, flip, TR_FROM_DN);
free (visited);
free (mchain);
free (vert);
free (mon);
/* return the number of rects created */
return size;
}
/* recursively visit all the trapezoids */
static int
traverse_polygon (int* visited, boxf* decomp, int size, segment_t* seg, trap_t* tr,
int mcur, int trnum, int from, int flip, int dir)
{
trap_t *t = &tr[trnum];
int mnew;
int v0, v1;
int retval;
int do_switch = FALSE;
if ((trnum <= 0) || visited[trnum])
return size;
visited[trnum] = TRUE;
if ((t->hi.y > t->lo.y) &&
(seg[t->lseg].v0.x == seg[t->lseg].v1.x) &&
(seg[t->rseg].v0.x == seg[t->rseg].v1.x)) {
if (flip) {
decomp[size].LL.x = t->lo.y;
decomp[size].LL.y = -seg[t->rseg].v0.x;
decomp[size].UR.x = t->hi.y;
decomp[size].UR.y = -seg[t->lseg].v0.x;
} else {
decomp[size].LL.x = seg[t->lseg].v0.x;
decomp[size].LL.y = t->lo.y;
decomp[size].UR.x = seg[t->rseg].v0.x;
decomp[size].UR.y = t->hi.y;
}
size++;
}
/* We have much more information available here. */
/* rseg: goes upwards */
/* lseg: goes downwards */
/* Initially assume that dir = TR_FROM_DN (from the left) */
/* Switch v0 and v1 if necessary afterwards */
/* special cases for triangles with cusps at the opposite ends. */
/* take care of this first */
if ((t->u0 <= 0) && (t->u1 <= 0))
{
if ((t->d0 > 0) && (t->d1 > 0)) /* downward opening triangle */
{
v0 = tr[t->d1].lseg;
v1 = t->lseg;
if (from == t->d1)
{
do_switch = TRUE;
mnew = make_new_monotone_poly(mcur, v1, v0);
size = traverse_polygon (visited, decomp, size, seg, tr, mcur, t->d1, trnum, flip, TR_FROM_UP);
size = traverse_polygon (visited, decomp, size, seg, tr, mnew, t->d0, trnum, flip, TR_FROM_UP);
}
else
{
mnew = make_new_monotone_poly(mcur, v0, v1);
size = traverse_polygon (visited, decomp, size, seg, tr, mcur, t->d0, trnum, flip, TR_FROM_UP);
size = traverse_polygon (visited, decomp, size, seg, tr, mnew, t->d1, trnum, flip, TR_FROM_UP);
}
}
else
{
retval = SP_NOSPLIT; /* Just traverse all neighbours */
size = traverse_polygon (visited, decomp, size, seg, tr, mcur, t->u0, trnum, flip, TR_FROM_DN);
size = traverse_polygon (visited, decomp, size, seg, tr, mcur, t->u1, trnum, flip, TR_FROM_DN);
size = traverse_polygon (visited, decomp, size, seg, tr, mcur, t->d0, trnum, flip, TR_FROM_UP);
size = traverse_polygon (visited, decomp, size, seg, tr, mcur, t->d1, trnum, flip, TR_FROM_UP);
}
}
else if ((t->d0 <= 0) && (t->d1 <= 0))
{
if ((t->u0 > 0) && (t->u1 > 0)) /* upward opening triangle */
{
v0 = t->rseg;
v1 = tr[t->u0].rseg;
if (from == t->u1)
{
do_switch = TRUE;
mnew = make_new_monotone_poly(mcur, v1, v0);
size = traverse_polygon (visited, decomp, size, seg, tr, mcur, t->u1, trnum, flip, TR_FROM_DN);
size = traverse_polygon (visited, decomp, size, seg, tr, mnew, t->u0, trnum, flip, TR_FROM_DN);
}
else
{
mnew = make_new_monotone_poly(mcur, v0, v1);
size = traverse_polygon (visited, decomp, size, seg, tr, mcur, t->u0, trnum, flip, TR_FROM_DN);
size = traverse_polygon (visited, decomp, size, seg, tr, mnew, t->u1, trnum, flip, TR_FROM_DN);
}
}
else
{
retval = SP_NOSPLIT; /* Just traverse all neighbours */
size = traverse_polygon (visited, decomp, size, seg, tr, mcur, t->u0, trnum, flip, TR_FROM_DN);
size = traverse_polygon (visited, decomp, size, seg, tr, mcur, t->u1, trnum, flip, TR_FROM_DN);
size = traverse_polygon (visited, decomp, size, seg, tr, mcur, t->d0, trnum, flip, TR_FROM_UP);
size = traverse_polygon (visited, decomp, size, seg, tr, mcur, t->d1, trnum, flip, TR_FROM_UP);
}
}
else if ((t->u0 > 0) && (t->u1 > 0))
{
if ((t->d0 > 0) && (t->d1 > 0)) /* downward + upward cusps */
{
v0 = tr[t->d1].lseg;
v1 = tr[t->u0].rseg;
retval = SP_2UP_2DN;
if (((dir == TR_FROM_DN) && (t->d1 == from)) ||
((dir == TR_FROM_UP) && (t->u1 == from)))
{
do_switch = TRUE;
mnew = make_new_monotone_poly(mcur, v1, v0);
size = traverse_polygon (visited, decomp, size, seg, tr, mcur, t->u1, trnum, flip, TR_FROM_DN);
size = traverse_polygon (visited, decomp, size, seg, tr, mcur, t->d1, trnum, flip, TR_FROM_UP);
size = traverse_polygon (visited, decomp, size, seg, tr, mnew, t->u0, trnum, flip, TR_FROM_DN);
size = traverse_polygon (visited, decomp, size, seg, tr, mnew, t->d0, trnum, flip, TR_FROM_UP);
}
else
{
mnew = make_new_monotone_poly(mcur, v0, v1);
size = traverse_polygon (visited, decomp, size, seg, tr, mcur, t->u0, trnum, flip, TR_FROM_DN);
size = traverse_polygon (visited, decomp, size, seg, tr, mcur, t->d0, trnum, flip, TR_FROM_UP);
size = traverse_polygon (visited, decomp, size, seg, tr, mnew, t->u1, trnum, flip, TR_FROM_DN);
size = traverse_polygon (visited, decomp, size, seg, tr, mnew, t->d1, trnum, flip, TR_FROM_UP);
}
}
else /* only downward cusp */
{
if (_equal_to(&t->lo, &seg[t->lseg].v1))
{
v0 = tr[t->u0].rseg;
v1 = seg[t->lseg].next;
retval = SP_2UP_LEFT;
if ((dir == TR_FROM_UP) && (t->u0 == from))
{
do_switch = TRUE;
mnew = make_new_monotone_poly(mcur, v1, v0);
size = traverse_polygon (visited, decomp, size, seg, tr, mcur, t->u0, trnum, flip, TR_FROM_DN);
size = traverse_polygon (visited, decomp, size, seg, tr, mnew, t->d0, trnum, flip, TR_FROM_UP);
size = traverse_polygon (visited, decomp, size, seg, tr, mnew, t->u1, trnum, flip, TR_FROM_DN);
size = traverse_polygon (visited, decomp, size, seg, tr, mnew, t->d1, trnum, flip, TR_FROM_UP);
}
else
{
mnew = make_new_monotone_poly(mcur, v0, v1);
size = traverse_polygon (visited, decomp, size, seg, tr, mcur, t->u1, trnum, flip, TR_FROM_DN);
size = traverse_polygon (visited, decomp, size, seg, tr, mcur, t->d0, trnum, flip, TR_FROM_UP);
size = traverse_polygon (visited, decomp, size, seg, tr, mcur, t->d1, trnum, flip, TR_FROM_UP);
size = traverse_polygon (visited, decomp, size, seg, tr, mnew, t->u0, trnum, flip, TR_FROM_DN);
}
}
else
{
v0 = t->rseg;
v1 = tr[t->u0].rseg;
retval = SP_2UP_RIGHT;
if ((dir == TR_FROM_UP) && (t->u1 == from))
{
do_switch = TRUE;
mnew = make_new_monotone_poly(mcur, v1, v0);
size = traverse_polygon (visited, decomp, size, seg, tr, mcur, t->u1, trnum, flip, TR_FROM_DN);
size = traverse_polygon (visited, decomp, size, seg, tr, mnew, t->d1, trnum, flip, TR_FROM_UP);
size = traverse_polygon (visited, decomp, size, seg, tr, mnew, t->d0, trnum, flip, TR_FROM_UP);
size = traverse_polygon (visited, decomp, size, seg, tr, mnew, t->u0, trnum, flip, TR_FROM_DN);
}
else
{
mnew = make_new_monotone_poly(mcur, v0, v1);
size = traverse_polygon (visited, decomp, size, seg, tr, mcur, t->u0, trnum, flip, TR_FROM_DN);
size = traverse_polygon (visited, decomp, size, seg, tr, mcur, t->d0, trnum, flip, TR_FROM_UP);
size = traverse_polygon (visited, decomp, size, seg, tr, mcur, t->d1, trnum, flip, TR_FROM_UP);
size = traverse_polygon (visited, decomp, size, seg, tr, mnew, t->u1, trnum, flip, TR_FROM_DN);
}
}
}
}
else if ((t->u0 > 0) || (t->u1 > 0)) /* no downward cusp */
{
if ((t->d0 > 0) && (t->d1 > 0)) /* only upward cusp */
{
if (_equal_to(&t->hi, &seg[t->lseg].v0))
{
v0 = tr[t->d1].lseg;
v1 = t->lseg;
retval = SP_2DN_LEFT;
if (!((dir == TR_FROM_DN) && (t->d0 == from)))
{
do_switch = TRUE;
mnew = make_new_monotone_poly(mcur, v1, v0);
size = traverse_polygon (visited, decomp, size, seg, tr, mcur, t->u1, trnum, flip, TR_FROM_DN);
size = traverse_polygon (visited, decomp, size, seg, tr, mcur, t->d1, trnum, flip, TR_FROM_UP);
size = traverse_polygon (visited, decomp, size, seg, tr, mcur, t->u0, trnum, flip, TR_FROM_DN);
size = traverse_polygon (visited, decomp, size, seg, tr, mnew, t->d0, trnum, flip, TR_FROM_UP);
}
else
{
mnew = make_new_monotone_poly(mcur, v0, v1);
size = traverse_polygon (visited, decomp, size, seg, tr, mcur, t->d0, trnum, flip, TR_FROM_UP);
size = traverse_polygon (visited, decomp, size, seg, tr, mnew, t->u0, trnum, flip, TR_FROM_DN);
size = traverse_polygon (visited, decomp, size, seg, tr, mnew, t->u1, trnum, flip, TR_FROM_DN);
size = traverse_polygon (visited, decomp, size, seg, tr, mnew, t->d1, trnum, flip, TR_FROM_UP);
}
}
else
{
v0 = tr[t->d1].lseg;
v1 = seg[t->rseg].next;
retval = SP_2DN_RIGHT;
if ((dir == TR_FROM_DN) && (t->d1 == from))
{
do_switch = TRUE;
mnew = make_new_monotone_poly(mcur, v1, v0);
size = traverse_polygon (visited, decomp, size, seg, tr, mcur, t->d1, trnum, flip, TR_FROM_UP);
size = traverse_polygon (visited, decomp, size, seg, tr, mnew, t->u1, trnum, flip, TR_FROM_DN);
size = traverse_polygon (visited, decomp, size, seg, tr, mnew, t->u0, trnum, flip, TR_FROM_DN);
size = traverse_polygon (visited, decomp, size, seg, tr, mnew, t->d0, trnum, flip, TR_FROM_UP);
}
else
{
mnew = make_new_monotone_poly(mcur, v0, v1);
size = traverse_polygon (visited, decomp, size, seg, tr, mcur, t->u0, trnum, flip, TR_FROM_DN);
size = traverse_polygon (visited, decomp, size, seg, tr, mcur, t->d0, trnum, flip, TR_FROM_UP);
size = traverse_polygon (visited, decomp, size, seg, tr, mcur, t->u1, trnum, flip, TR_FROM_DN);
size = traverse_polygon (visited, decomp, size, seg, tr, mnew, t->d1, trnum, flip, TR_FROM_UP);
}
}
}
else /* no cusp */
{
if (_equal_to(&t->hi, &seg[t->lseg].v0) &&
_equal_to(&t->lo, &seg[t->rseg].v0))
{
v0 = t->rseg;
v1 = t->lseg;
retval = SP_SIMPLE_LRDN;
if (dir == TR_FROM_UP)
{
do_switch = TRUE;
mnew = make_new_monotone_poly(mcur, v1, v0);
size = traverse_polygon (visited, decomp, size, seg, tr, mcur, t->u0, trnum, flip, TR_FROM_DN);
size = traverse_polygon (visited, decomp, size, seg, tr, mcur, t->u1, trnum, flip, TR_FROM_DN);
size = traverse_polygon (visited, decomp, size, seg, tr, mnew, t->d1, trnum, flip, TR_FROM_UP);
size = traverse_polygon (visited, decomp, size, seg, tr, mnew, t->d0, trnum, flip, TR_FROM_UP);
}
else
{
mnew = make_new_monotone_poly(mcur, v0, v1);
size = traverse_polygon (visited, decomp, size, seg, tr, mcur, t->d1, trnum, flip, TR_FROM_UP);
size = traverse_polygon (visited, decomp, size, seg, tr, mcur, t->d0, trnum, flip, TR_FROM_UP);
size = traverse_polygon (visited, decomp, size, seg, tr, mnew, t->u0, trnum, flip, TR_FROM_DN);
size = traverse_polygon (visited, decomp, size, seg, tr, mnew, t->u1, trnum, flip, TR_FROM_DN);
}
}
else if (_equal_to(&t->hi, &seg[t->rseg].v1) &&
_equal_to(&t->lo, &seg[t->lseg].v1))
{
v0 = seg[t->rseg].next;
v1 = seg[t->lseg].next;
retval = SP_SIMPLE_LRUP;
if (dir == TR_FROM_UP)
{
do_switch = TRUE;
mnew = make_new_monotone_poly(mcur, v1, v0);
size = traverse_polygon (visited, decomp, size, seg, tr, mcur, t->u0, trnum, flip, TR_FROM_DN);
size = traverse_polygon (visited, decomp, size, seg, tr, mcur, t->u1, trnum, flip, TR_FROM_DN);
size = traverse_polygon (visited, decomp, size, seg, tr, mnew, t->d1, trnum, flip, TR_FROM_UP);
size = traverse_polygon (visited, decomp, size, seg, tr, mnew, t->d0, trnum, flip, TR_FROM_UP);
}
else
{
mnew = make_new_monotone_poly(mcur, v0, v1);
size = traverse_polygon (visited, decomp, size, seg, tr, mcur, t->d1, trnum, flip, TR_FROM_UP);
size = traverse_polygon (visited, decomp, size, seg, tr, mcur, t->d0, trnum, flip, TR_FROM_UP);
size = traverse_polygon (visited, decomp, size, seg, tr, mnew, t->u0, trnum, flip, TR_FROM_DN);
size = traverse_polygon (visited, decomp, size, seg, tr, mnew, t->u1, trnum, flip, TR_FROM_DN);
}
}
else /* no split possible */
{
retval = SP_NOSPLIT;
size = traverse_polygon (visited, decomp, size, seg, tr, mcur, t->u0, trnum, flip, TR_FROM_DN);
size = traverse_polygon (visited, decomp, size, seg, tr, mcur, t->d0, trnum, flip, TR_FROM_UP);
size = traverse_polygon (visited, decomp, size, seg, tr, mcur, t->u1, trnum, flip, TR_FROM_DN);
size = traverse_polygon (visited, decomp, size, seg, tr, mcur, t->d1, trnum, flip, TR_FROM_UP);
}
}
}
return size;
}
int monotonate_trapezoids(
int n)
{
register int i;
int tr_start;
memset((void *)vert, 0, sizeof(vert));
memset((void *)visited, 0, sizeof(visited));
memset((void *)mchain, 0, sizeof(mchain));
memset((void *)mon, 0, sizeof(mon));
/* First locate a trapezoid which lies inside the polygon */
/* and which is triangular */
for (i = 0; i < TRSIZE; i++)
if (inside_polygon(&tr[i]))
break;
tr_start = i;
/* Initialise the mon data-structure and start spanning all the */
/* trapezoids within the polygon */
#if 0
for (i = 1; i <= n; i++)
{
mchain[i].prev = i - 1;
mchain[i].next = i + 1;
mchain[i].vnum = i;
vert[i].pt = seg[i].v0;
vert[i].vnext[0] = i + 1; /* next vertex */
vert[i].vpos[0] = i; /* locn. of next vertex */
vert[i].nextfree = 1;
}
mchain[1].prev = n;
mchain[n].next = 1;
vert[n].vnext[0] = 1;
vert[n].vpos[0] = n;
chain_idx = n;
mon_idx = 0;
mon[0] = 1; /* position of any vertex in the first */
/* chain */
#else
for (i = 1; i <= n; i++)
{
mchain[i].prev = seg[i].prev;
mchain[i].next = seg[i].next;
mchain[i].vnum = i;
vert[i].pt = seg[i].v0;
vert[i].vnext[0] = seg[i].next; /* next vertex */
vert[i].vpos[0] = i; /* locn. of next vertex */
vert[i].nextfree = 1;
}
chain_idx = n;
mon_idx = 0;
mon[0] = 1; /* position of any vertex in the first */
/* chain */
#endif
/* traverse the polygon */
if (tr[tr_start].u0 > 0)
traverse_polygon(0, tr_start, tr[tr_start].u0, TR_FROM_UP);
else if (tr[tr_start].d0 > 0)
traverse_polygon(0, tr_start, tr[tr_start].d0, TR_FROM_DN);
/* return the number of polygons created */
return newmon();
}
