PostGIS  2.1.10dev-r@@SVN_REVISION@@
int lw_arc_side ( const POINT2D A1,
const POINT2D A2,
const POINT2D A3,
const POINT2D Q 
)

Definition at line 179 of file lwalgorithm.c.

References distance2d_pt_pt(), lw_arc_center(), and lw_segment_side().

Referenced by ptarrayarc_contains_point_partial().

180 {
181  POINT2D C;
182  double radius_A;
183  double side_Q, side_A2;
184  double d;
185 
186  side_Q = lw_segment_side(A1, A3, Q);
187  radius_A = lw_arc_center(A1, A2, A3, &C);
188  side_A2 = lw_segment_side(A1, A3, A2);
189 
190  /* Linear case */
191  if ( radius_A < 0 )
192  return side_Q;
193 
194  d = distance2d_pt_pt(Q, &C);
195 
196  /* Q is on the arc boundary */
197  if ( d == radius_A && side_Q == side_A2 )
198  {
199  return 0;
200  }
201 
202  /* Q on A1-A3 line, so its on opposite side to A2 */
203  if ( side_Q == 0 )
204  {
205  return -1 * side_A2;
206  }
207 
208  /*
209  * Q is inside the arc boundary, so it's not on the side we
210  * might think from examining only the end points
211  */
212  if ( d < radius_A && side_Q == side_A2 )
213  {
214  side_Q *= -1;
215  }
216 
217  return side_Q;
218 }
double distance2d_pt_pt(const POINT2D *p1, const POINT2D *p2)
The old function nessecary for ptarray_segmentize2d in ptarray.c.
Definition: measures.c:2123
double lw_arc_center(const POINT2D *p1, const POINT2D *p2, const POINT2D *p3, POINT2D *result)
Determines the center of the circle defined by the three given points.
Definition: lwalgorithm.c:228
int lw_segment_side(const POINT2D *p1, const POINT2D *p2, const POINT2D *q)
lw_segment_side()
Definition: lwalgorithm.c:62

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