/* Store in the rightface field of each edge the number of the face on
the right hand side of that edge. Faces are numbered 0,1,.... Also
store in facestart[i] an example of an edge in the clockwise orientation
of the face boundary, and the size of the face in facesize[i], for each i.
Returns the number of faces. */
void makeDual() {
register int i, sz;
register EDGE *e, *ex, *ef, *efx;
RESETMARKS;
nf = 0;
for (i = 0; i < nv; ++i) {
e = ex = firstedge[i];
do {
if (!ISMARKEDLO(e)) {
facestart[nf] = ef = efx = e;
faceSets[nf] = EMPTY_SET;
sz = 0;
do {
ef->rightface = nf;
ADD(faceSets[nf], ef->end);
MARKLO(ef);
ef = ef->inverse->prev;
++sz;
} while (ef != efx);
faceSize[nf] = sz;
++nf;
}
e = e->next;
} while (e != ex);
}
}
/* Store in the rightface field of each edge the number of the face on
the right hand side of that edge. Faces are numbered 0,1,.... Also
store in facestart[i] an example of an edge in the clockwise orientation
of the face boundary, and the size of the face in facesize[i], for each i.
Returns the number of faces. */
void makeDual(PLANE_GRAPH *pg) {
register int i, sz;
register PG_EDGE *e, *ex, *ef, *efx;
RESETMARKS(pg);
//first allocate the memory to store faces if this has not yet been done
int maxf = 2*pg->maxn - 4;
if(pg->maxf < maxf){
if(pg->facestart!=NULL){
free(pg->facestart);
}
if(pg->faceSize!=NULL){
free(pg->faceSize);
}
pg->maxf = maxf;
pg->facestart = (PG_EDGE **)malloc(sizeof(PG_EDGE *)*maxf);
if(pg->facestart == NULL){
pg->maxf = 0;
return;
}
pg->faceSize = (int *)malloc(sizeof(int)*maxf);
if(pg->faceSize == NULL){
pg->maxf = 0;
free(pg->facestart);
return;
}
}
int nf = 0;
for (i = 0; i < pg->nv; ++i) {
e = ex = pg->firstedge[i];
do {
if (!ISMARKEDLO(e)) {
pg->facestart[nf] = ef = efx = e;
sz = 0;
do {
ef->rightface = nf;
MARKLO(ef);
ef = ef->inverse->prev;
++sz;
} while (ef != efx);
pg->faceSize[nf] = sz;
++nf;
}
e = e->next;
} while (e != ex);
}
pg->nf = nf;
pg->dualComputed = TRUE;
}
void walk_faces(int i, int face_colour)
{
int r, c, s;
int v1, v2, v3;
int a1, a2, a3;
vertices_of_face(i, &v1, &v2, &v3);
// If we have already visited this face then there
// is nothing to do here so leave.
if (ISMARKED(facestart[i])) return;
// Otherwise we tag this face and recurse on the
// three neighbours.
MARKLO(facestart[i]);
// printf("marking face %d\n", i);
// If all three vertices of this face are uncoloured
// then we are entering walk_faces for for the first time
// so we arbitrarily 3-colour the vertices of this face.
if (vertex_colour[v1] < 0 && vertex_colour[v2] < 0 && vertex_colour[v3] < 0) {
vertex_colour[v1] = 0;
vertex_colour[v2] = 1;
vertex_colour[v3] = 2;
} else if (vertex_colour[v1] >= 0 && vertex_colour[v2] >= 0 && vertex_colour[v3] >= 0) {
// Terminating case, do nothing.
} else {
// Two vertices must be coloured so we can colour the third.
if (vertex_colour[v1] >= 0 && vertex_colour[v2] >= 0) {
assert(vertex_colour[v3] < 0);
vertex_colour[v3] = other_colour(vertex_colour[v1], vertex_colour[v2]);
} else if (vertex_colour[v1] >= 0 && vertex_colour[v3] >= 0) {
assert(vertex_colour[v2] < 0);
vertex_colour[v2] = other_colour(vertex_colour[v1], vertex_colour[v3]);
} else if (vertex_colour[v2] >= 0 && vertex_colour[v3] >= 0) {
assert(vertex_colour[v1] < 0);
vertex_colour[v1] = other_colour(vertex_colour[v2], vertex_colour[v3]);
} else {
printf("%d, %d, %d\n", vertex_colour[v1], vertex_colour[v2], vertex_colour[v3]);
assert(FALSE);
}
}
ordered_triple(v1, v2, v3, &r, &c, &s);
// Have we seen the row label r before? If not, make a note of how
// we will really present it.
if (row_label[r] < 0) {
row_label[r] = max_row_label;
max_row_label++;
}
if (col_label[c] < 0) {
col_label[c] = max_col_label;
max_col_label++;
}
if (sym_label[s] < 0) {
sym_label[s] = max_sym_label;
max_sym_label++;
}
triple e;
e.x = row_label[r];
e.y = col_label[c];
e.z = sym_label[s];
if (face_colour == 0) {
T1[max_entry_index1] = e;
max_entry_index1++;
} else { // face_colour == 1
T2[max_entry_index2] = e;
max_entry_index2++;
}
// tags of the three adjacent faces
a1 = facestart[i]->invers->tag;
a2 = facestart[i]->invers->prev->invers->tag;
a3 = facestart[i]->invers->prev->invers->prev->invers->tag;
if (face_colour == 0) face_colour = 1;
else face_colour = 0;
walk_faces(a1, face_colour);
walk_faces(a2, face_colour);
walk_faces(a3, face_colour);
}
