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92 lines
3.4 KiB
C++
92 lines
3.4 KiB
C++
/*
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** License Applicability. Except to the extent portions of this file are
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** made subject to an alternative license as permitted in the SGI Free
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** Software License B, Version 1.1 (the "License"), the contents of this
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** file are subject only to the provisions of the License. You may not use
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** this file except in compliance with the License. You may obtain a copy
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** of the License at Silicon Graphics, Inc., attn: Legal Services, 1600
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** Amphitheatre Parkway, Mountain View, CA 94043-1351, or at:
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**
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** http://oss.sgi.com/projects/FreeB
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**
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** Note that, as provided in the License, the Software is distributed on an
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** "AS IS" basis, with ALL EXPRESS AND IMPLIED WARRANTIES AND CONDITIONS
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** DISCLAIMED, INCLUDING, WITHOUT LIMITATION, ANY IMPLIED WARRANTIES AND
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** CONDITIONS OF MERCHANTABILITY, SATISFACTORY QUALITY, FITNESS FOR A
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** PARTICULAR PURPOSE, AND NON-INFRINGEMENT.
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**
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** Original Code. The Original Code is: OpenGL Sample Implementation,
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** Version 1.2.1, released January 26, 2000, developed by Silicon Graphics,
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** Inc. The Original Code is Copyright (c) 1991-2000 Silicon Graphics, Inc.
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** Copyright in any portions created by third parties is as indicated
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** elsewhere herein. All Rights Reserved.
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**
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** Additional Notice Provisions: The application programming interfaces
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** established by SGI in conjunction with the Original Code are The
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** OpenGL(R) Graphics System: A Specification (Version 1.2.1), released
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** April 1, 1999; The OpenGL(R) Graphics System Utility Library (Version
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** 1.3), released November 4, 1998; and OpenGL(R) Graphics with the X
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** Window System(R) (Version 1.3), released October 19, 1998. This software
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** was created using the OpenGL(R) version 1.2.1 Sample Implementation
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** published by SGI, but has not been independently verified as being
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** compliant with the OpenGL(R) version 1.2.1 Specification.
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**
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** $Date$ $Revision: 1.1 $
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*/
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/*
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** $Header: /cygdrive/c/RCVS/CVS/ReactOS/reactos/lib/glu32/libnurbs/nurbtess/polyUtil.cc,v 1.1 2004/02/02 16:39:13 navaraf Exp $
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*/
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#include <stdlib.h>
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#include <stdio.h>
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#include "polyUtil.h"
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Real area(Real A[2], Real B[2], Real C[2])
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{
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Real Bx, By, Cx, Cy;
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Bx = B[0] - A[0];
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By = B[1] - A[1];
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Cx = C[0] - A[0];
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Cy = C[1] - A[1];
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return Bx*Cy - Cx*By;
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/* return (B[0]-A[0])*(C[1]-A[1]) - (C[0]-A[0])*(B[1]-A[1]);*/
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}
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/*given a directed line A->B, and a point P,
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*determine whether P is to the left of AB.
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*the line A->B (imagine it has beedn extended both
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*end to the infinity) divides the plan into two
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*half planes. When we walk from A to B, one
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*half is to the left and the other half is to the right.
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*return 1 if P is to the left.
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*if P is on AB, 0 is returned.
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*/
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Int pointLeftLine(Real A[2], Real B[2], Real P[2])
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{
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if(area(A, B, P) >0) return 1;
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else return 0;
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}
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/*given two directed line: A -> B -> C, and another point P.
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*determine whether P is to the left hand side of A->B->C.
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*Think of BA and BC extended as two rays. So that the plane is
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* divided into two parts. One part is to the left we walk from A
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*to B and to C, the other part is to the right.
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* In order for P to be the left, P must be either to the left
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*of
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*/
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Int pointLeft2Lines(Real A[2], Real B[2], Real C[2], Real P[2])
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{
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Int C_left_AB = (area(A, B, C)>0);
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Int P_left_AB = (area(A, B, P)>0);
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Int P_left_BC = (area(B, C, P)>0);
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if(C_left_AB)
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{
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return (P_left_AB && P_left_BC);
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}
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else
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return (P_left_AB || P_left_BC);
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}
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