P2trEdge*
p2tr_point_edge_cw (P2trPoint* self,
P2trEdge *e)
{
GList *node;
if (P2TR_EDGE_START(e) != self)
p2tr_exception_programmatic ("Not an edge of this point!");
node = g_list_find (self->outgoing_edges, e);
if (node == NULL)
p2tr_exception_programmatic ("Could not find the CW sibling edge"
"because the edge is not present in the outgoing-edges list!");
return (P2trEdge*) g_list_cyclic_prev (self->outgoing_edges, node);
}
/* ^ e1
* /
* /_ e1.Tri (e2.Mirror.Tri)
* / |
* *---------> e2
*
* Check if the angle marked is a part of the triangulation
* domain
*/
static gboolean
p2tr_cluster_cw_tri_between_is_in_domain (P2trEdge *e1, P2trEdge *e2)
{
if (P2TR_EDGE_START(e1) != P2TR_EDGE_START(e2) || e1->tri != e2->mirror->tri)
p2tr_exception_programmatic ("Non clockwise adjacent edges!");
return e1->tri != NULL;
}
void
_p2tr_point_remove_edge (P2trPoint *self, P2trEdge* e)
{
GList *node;
if (P2TR_EDGE_START(e) != self)
p2tr_exception_programmatic ("Could not remove the given outgoing "
"edge because doesn't start on this point!");
node = g_list_find (self->outgoing_edges, e);
if (node == NULL)
p2tr_exception_programmatic ("Could not remove the given outgoing "
"edge because it's not present in the outgoing-edges list!");
self->outgoing_edges = g_list_delete_link (self->outgoing_edges, node);
p2tr_edge_unref (e);
}
P2trEdge*
p2tr_point_get_edge_to (P2trPoint *start,
P2trPoint *end)
{
P2trEdge* result = p2tr_point_has_edge_to (start, end);
if (result == NULL)
p2tr_exception_programmatic ("Tried to get an edge that doesn't exist!");
else
return result;
}
/**
* Return the edge cluster of the specified edge from the specified end
* point. THE EDGES IN THE CLUSTER MUST BE UNREFFED!
* @param[in] P The point which is shared between all edges of the cluster
* @param[in] E The edge whose cluster should be returned
* @return The cluster of @ref E from the point @ref P
*/
P2trCluster*
p2tr_cluster_get_for (P2trPoint *P,
P2trEdge *E)
{
P2trCluster *cluster = g_slice_new (P2trCluster);
gdouble temp_angle;
P2trEdge *current, *next;
cluster->min_angle = G_MAXDOUBLE;
g_queue_init (&cluster->edges);
if (P == E->end)
P = P2TR_EDGE_START (E);
else if (P != P2TR_EDGE_START (E))
p2tr_exception_programmatic ("Unexpected point for the edge!");
g_queue_push_head (&cluster->edges, E);
current = E;
next = p2tr_point_edge_cw (P, current);
while (next != g_queue_peek_head (&cluster->edges)
&& (temp_angle = p2tr_edge_angle_between (current->mirror, next)) <= P2TR_CLUSTER_LIMIT_ANGLE
&& p2tr_cluster_cw_tri_between_is_in_domain (current, next))
{
g_queue_push_tail (&cluster->edges, next);
p2tr_edge_ref (next);
current = next;
next = p2tr_point_edge_cw (P, current);
cluster->min_angle = MIN (cluster->min_angle, temp_angle);
}
current = E;
next = p2tr_point_edge_ccw(P, current);
while (next != g_queue_peek_tail (&cluster->edges)
&& (temp_angle = p2tr_edge_angle_between (current->mirror, next)) <= P2TR_CLUSTER_LIMIT_ANGLE
&& p2tr_cluster_cw_tri_between_is_in_domain (next, current))
{
g_queue_push_head (&cluster->edges, next);
p2tr_edge_ref (next);
current = next;
next = p2tr_point_edge_ccw (P, current);
cluster->min_angle = MIN(cluster->min_angle, temp_angle);
}
return cluster;
}
gdouble
p2tr_edge_angle_between(P2trEdge *e1, P2trEdge *e2)
{
/* A = E1.angle, a = abs (A)
* B = E1.angle, b = abs (B)
*
* W is the angle we wish to find. Note the fact that we want
* to find the angle so that the edges go CLOCKWISE around it.
*
* Case 1: Signs of A and B agree | Case 2: Signs of A and B disagree
* and A > 0 | and A > 0
* |
* a = A, b = B | a = A, b = -B
* ^^ |
* E2 // | /
* //\ | /
* //b| | /a
* - - - - * - |W- - - - - - - - | - - - - * - - - -
* ^^a'| | ^^ \\b
* ||_/ | // W \\
* E1 ||\ | E1 // \_/ \\ E2
* '||a\ | // \\
* - - - - - - | // vv
* |
* W = A' + B = (180 - A) + B | W = 180 - (a + b) = 180 - (A - B)
* W = 180 - A + B | W = 180 - A + B
*
* By the illustration above, we can see that in general the angle W
* can be computed by W = 180 - A + B in every case. The only thing to
* note is that the range of the result of the computation is
* [180 - 360, 180 + 360] = [-180, +540] so we may need to subtract
* 360 to put it back in the range [-180, +180].
*/
gdouble result;
if (e1->end != P2TR_EDGE_START(e2))
p2tr_exception_programmatic ("The end-point of the first edge isn't"
" the end-point of the second edge!");
result = G_PI - e1->angle + e2->angle;
if (result > 2 * G_PI)
result -= 2 * G_PI;
return result;
}
/**
* Triangulate a polygon by creating edges to a center point.
* 1. If there is a NULL point in the polygon, two triangles are not
* created (these are the two that would have used it)
* 2. THE RETURNED TRIANGLES MUST BE UNREFFED!
*/
static GList*
p2tr_cdt_triangulate_fan (P2trCDT *self,
P2trPoint *center,
GList *edge_pts)
{
GList *new_tris = NULL;
GList *iter;
/* We can not triangulate unless at least two points are given */
if (edge_pts == NULL || edge_pts->next == NULL)
{
p2tr_exception_programmatic ("Not enough points to triangulate as"
" a star!");
}
for (iter = edge_pts; iter != NULL; iter = iter->next)
{
P2trPoint *A = (P2trPoint*) iter->data;
P2trPoint *B = (P2trPoint*) g_list_cyclic_next (edge_pts, iter)->data;
P2trEdge *AB, *BC, *CA;
P2trTriangle *tri;
if (A == NULL || B == NULL)
continue;
AB = p2tr_point_get_edge_to (A, B);
BC = p2tr_mesh_new_or_existing_edge (self->mesh, B, center, FALSE);
CA = p2tr_mesh_new_or_existing_edge (self->mesh, center, A, FALSE);
tri = p2tr_mesh_new_triangle (self->mesh, AB, BC, CA);
new_tris = g_list_prepend (new_tris, tri);
p2tr_edge_unref (BC);
p2tr_edge_unref (CA);
}
return new_tris;
}
/**
* Triangulate a polygon by creating edges to a center point.
* 1. If there is a NULL point in the polygon, two triangles are not
* created (these are the two that would have used it)
* 2. THE RETURNED EDGES MUST BE UNREFFED!
*/
static P2trVEdgeSet*
p2tr_cdt_triangulate_fan (P2trCDT *self,
P2trPoint *center,
GList *edge_pts)
{
P2trVEdgeSet* fan_edges = p2tr_vedge_set_new ();
GList *iter;
/* We can not triangulate unless at least two points are given */
if (edge_pts == NULL || edge_pts->next == NULL)
{
p2tr_exception_programmatic ("Not enough points to triangulate as"
" a star!");
}
for (iter = edge_pts; iter != NULL; iter = iter->next)
{
P2trPoint *A = (P2trPoint*) iter->data;
P2trPoint *B = (P2trPoint*) g_list_cyclic_next (edge_pts, iter)->data;
P2trEdge *AB, *BC, *CA;
if (A == NULL || B == NULL)
continue;
AB = p2tr_point_get_edge_to (A, B, TRUE);
BC = p2tr_mesh_new_or_existing_edge (self->mesh, B, center, FALSE);
CA = p2tr_mesh_new_or_existing_edge (self->mesh, center, A, FALSE);
p2tr_triangle_unref (p2tr_mesh_new_triangle (self->mesh, AB, BC, CA));
p2tr_vedge_set_add (fan_edges, CA);
p2tr_vedge_set_add (fan_edges, BC);
p2tr_vedge_set_add (fan_edges, AB);
}
return fan_edges;
}
