void
p2tr_math_triangle_circumcircle (const P2trVector2 *A,
const P2trVector2 *B,
const P2trVector2 *C,
P2trCircle *circle)
{
/* | Ax Bx Cx |
* D = + | Ay By Cy | * 2
* | +1 +1 +1 |
*
* | Asq Bsq Csq |
* X = + | Ay By Cy | / D
* | 1 1 1 |
*
* | Asq Bsq Csq |
* Y = - | Ax Bx Cx | / D
* | 1 1 1 |
*/
gdouble Asq = P2TR_VECTOR2_LEN_SQ (A);
gdouble Bsq = P2TR_VECTOR2_LEN_SQ (B);
gdouble Csq = P2TR_VECTOR2_LEN_SQ (C);
gdouble invD = 1 / (2 * p2tr_matrix_det3 (
A->x, B->x, C->x,
A->y, B->y, C->y,
1, 1, 1));
circle->center.x = + p2tr_matrix_det3 (
Asq, Bsq, Csq,
A->y, B->y, C->y,
1, 1, 1) * invD;
circle->center.y = - p2tr_matrix_det3 (
Asq, Bsq, Csq,
A->x, B->x, C->x,
1, 1, 1) * invD;
circle->radius = sqrt (P2TR_VECTOR2_DISTANCE_SQ (A, &circle->center));
}
static gboolean
find_closest_intersection (P2trPSLG *pslg,
P2trLine *line,
P2trVector2 *close_to,
P2trVector2 *dest)
{
gdouble distance_sq = G_MAXDOUBLE;
gboolean found = FALSE;
const P2trBoundedLine *pslg_line = NULL;
P2trPSLGIter pslg_iter;
P2trVector2 temp;
p2tr_pslg_iter_init (&pslg_iter, pslg);
while (p2tr_pslg_iter_next (&pslg_iter, &pslg_line))
{
if (p2tr_line_intersection (&pslg_line->infinite, line, &temp)
== P2TR_LINE_RELATION_INTERSECTING)
{
gdouble test_distance_sq = P2TR_VECTOR2_DISTANCE_SQ (&temp, close_to);
found = TRUE;
if (test_distance_sq < distance_sq)
{
distance_sq = test_distance_sq;
}
}
}
if (found && dest != NULL)
p2tr_vector2_copy (dest, &temp);
return found;
}