Find if a point is within a triangle: Difference between revisions
Content added Content deleted
(Added Common Lisp) |
|||
| Line 283: | Line 283: | ||
; We use the sign of the determinant of vectors (AB,AM), where M(X,Y) is the query point: |
; We use the sign of the determinant of vectors (AB,AM), where M(X,Y) is the query point: |
||
; position = sign((Bx - Ax) * (Y - Ay) - (By - Ay) * (X - Ax)) |
; position = sign((Bx - Ax) * (Y - Ay) - (By - Ay) * (X - Ax)) |
||
( |
(signum (- (* (- (car B) (car A)) |
||
(- (cdr P) (cdr A)) ) |
(- (cdr P) (cdr A)) ) |
||
(* (- (cdr B) (cdr A)) |
(* (- (cdr B) (cdr A)) |
||
(- (car P) (car A)) )))) |
(- (car P) (car A)) )))) |
||
(defun sign (x) |
|||
(if (plusp x) |
|||
1 |
|||
(if (minusp x) |
|||
-1 |
|||
0 ))) |
|||
</lang> |
</lang> |
||
{{out}} |
{{out}} |
||
| Line 313: | Line 306: | ||
NIL |
NIL |
||
</pre> |
</pre> |
||
=={{header|D}}== |
=={{header|D}}== |
||