| /* |
| ** License Applicability. Except to the extent portions of this file are |
| ** made subject to an alternative license as permitted in the SGI Free |
| ** Software License B, Version 1.1 (the "License"), the contents of this |
| ** file are subject only to the provisions of the License. You may not use |
| ** this file except in compliance with the License. You may obtain a copy |
| ** of the License at Silicon Graphics, Inc., attn: Legal Services, 1600 |
| ** Amphitheatre Parkway, Mountain View, CA 94043-1351, or at: |
| ** |
| ** http://oss.sgi.com/projects/FreeB |
| ** |
| ** Note that, as provided in the License, the Software is distributed on an |
| ** "AS IS" basis, with ALL EXPRESS AND IMPLIED WARRANTIES AND CONDITIONS |
| ** DISCLAIMED, INCLUDING, WITHOUT LIMITATION, ANY IMPLIED WARRANTIES AND |
| ** CONDITIONS OF MERCHANTABILITY, SATISFACTORY QUALITY, FITNESS FOR A |
| ** PARTICULAR PURPOSE, AND NON-INFRINGEMENT. |
| ** |
| ** Original Code. The Original Code is: OpenGL Sample Implementation, |
| ** Version 1.2.1, released January 26, 2000, developed by Silicon Graphics, |
| ** Inc. The Original Code is Copyright (c) 1991-2000 Silicon Graphics, Inc. |
| ** Copyright in any portions created by third parties is as indicated |
| ** elsewhere herein. All Rights Reserved. |
| ** |
| ** Additional Notice Provisions: The application programming interfaces |
| ** established by SGI in conjunction with the Original Code are The |
| ** OpenGL(R) Graphics System: A Specification (Version 1.2.1), released |
| ** April 1, 1999; The OpenGL(R) Graphics System Utility Library (Version |
| ** 1.3), released November 4, 1998; and OpenGL(R) Graphics with the X |
| ** Window System(R) (Version 1.3), released October 19, 1998. This software |
| ** was created using the OpenGL(R) version 1.2.1 Sample Implementation |
| ** published by SGI, but has not been independently verified as being |
| ** compliant with the OpenGL(R) version 1.2.1 Specification. |
| ** |
| ** $Date: 2012/03/29 17:22:17 $ $Revision: 1.1.1.1 $ |
| */ |
| /* |
| ** $Header: /cvs/bao-parsec/pkgs/libs/mesa/src/src/glu/sgi/libnurbs/nurbtess/polyUtil.cc,v 1.1.1.1 2012/03/29 17:22:17 uid42307 Exp $ |
| */ |
| |
| #include <stdlib.h> |
| #include <stdio.h> |
| |
| #include "polyUtil.h" |
| |
| Real area(Real A[2], Real B[2], Real C[2]) |
| { |
| Real Bx, By, Cx, Cy; |
| Bx = B[0] - A[0]; |
| By = B[1] - A[1]; |
| Cx = C[0] - A[0]; |
| Cy = C[1] - A[1]; |
| return Bx*Cy - Cx*By; |
| |
| /* return (B[0]-A[0])*(C[1]-A[1]) - (C[0]-A[0])*(B[1]-A[1]);*/ |
| } |
| |
| /*given a directed line A->B, and a point P, |
| *determine whether P is to the left of AB. |
| *the line A->B (imagine it has beedn extended both |
| *end to the infinity) divides the plan into two |
| *half planes. When we walk from A to B, one |
| *half is to the left and the other half is to the right. |
| *return 1 if P is to the left. |
| *if P is on AB, 0 is returned. |
| */ |
| Int pointLeftLine(Real A[2], Real B[2], Real P[2]) |
| { |
| if(area(A, B, P) >0) return 1; |
| else return 0; |
| } |
| |
| /*given two directed line: A -> B -> C, and another point P. |
| *determine whether P is to the left hand side of A->B->C. |
| *Think of BA and BC extended as two rays. So that the plane is |
| * divided into two parts. One part is to the left we walk from A |
| *to B and to C, the other part is to the right. |
| * In order for P to be the left, P must be either to the left |
| *of |
| */ |
| Int pointLeft2Lines(Real A[2], Real B[2], Real C[2], Real P[2]) |
| { |
| Int C_left_AB = (area(A, B, C)>0); |
| Int P_left_AB = (area(A, B, P)>0); |
| Int P_left_BC = (area(B, C, P)>0); |
| |
| if(C_left_AB) |
| { |
| return (P_left_AB && P_left_BC); |
| } |
| else |
| return (P_left_AB || P_left_BC); |
| } |