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math2d.h

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00001 /*
00002     Copyright (C) 1998-2000 by Jorrit Tyberghein
00003     Largely rewritten by Ivan Avramovic <ivan@avramovic.com>
00004 
00005     This library is free software; you can redistribute it and/or
00006     modify it under the terms of the GNU Library General Public
00007     License as published by the Free Software Foundation; either
00008     version 2 of the License, or (at your option) any later version.
00009 
00010     This library is distributed in the hope that it will be useful,
00011     but WITHOUT ANY WARRANTY; without even the implied warranty of
00012     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00013     Library General Public License for more details.
00014 
00015     You should have received a copy of the GNU Library General Public
00016     License along with this library; if not, write to the Free
00017     Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
00018 */
00019 
00020 #ifndef __CS_MATH2D_H__
00021 #define __CS_MATH2D_H__
00022 
00029 // These are also defined in plane2.h
00030 #ifndef __CS_POLY_MACROS__
00031 #define __CS_POLY_MACROS__
00032 #define CS_POLY_IN 1
00033 #define CS_POLY_ON 0
00034 #define CS_POLY_OUT -1
00035 #endif
00036 
00037 #include "csextern.h"
00038 
00039 #include "csgeom/vector2.h"
00040 #include "csgeom/plane2.h"
00041 #include "csgeom/segment.h"
00042 
00043 class csBox2;
00044 class csPoly2D;
00045 
00050 class CS_CSGEOM_EXPORT csMath2
00051 {
00052 public:
00059   static int WhichSide2D (const csVector2& v,
00060                           const csVector2& s1, const csVector2& s2)
00061   {
00062     float k  = (s1.y - v.y)*(s2.x - s1.x);
00063     float k1 = (s1.x - v.x)*(s2.y - s1.y);
00064     if (k < k1) return -1;
00065     else if (k > k1) return 1;
00066     else return 0;
00067   }
00068 
00075   static int WhichSide2D (const csVector2& v,
00076                           const csSegment2& s)
00077   {
00078     return WhichSide2D (v, s.Start (), s.End ());
00079   }
00080 
00088   static int InPoly2D (const csVector2& v,
00089                        csVector2* P, int n, csBox2* bounding_box);
00090 
00096   static float Area2 (const csVector2& a,
00097                       const csVector2& b,
00098                       const csVector2& c)
00099   {
00100     return
00101       a.x * b.y - a.y * b.x +
00102       a.y * c.x - a.x * c.y +
00103       b.x * c.y - c.x * b.y;
00104   }
00105 
00111   static float Right (const csVector2& a,
00112                       const csVector2& b,
00113                       const csVector2& c)
00114   {
00115     return Area2 (a, b, c) <= -SMALL_EPSILON;
00116   }
00117 
00123   static float Left (const csVector2& a,
00124                      const csVector2& b,
00125                      const csVector2& c)
00126   {
00127     return Area2 (a, b, c) >= SMALL_EPSILON;
00128   }
00129 
00135   static bool Visible (const csVector2& p, const csPlane2& pl)
00136   { return pl.Classify (p) <= 0; }
00137 
00144   static bool PlanesEqual (const csPlane2& p1, const csPlane2& p2)
00145   {
00146     return ( ( p1.norm - p2.norm) < (float).001 ) &&
00147              (  ABS (p1.CC-p2.CC) < (float).001 );
00148   }
00149 
00155   static bool PlanesClose (const csPlane2& p1, const csPlane2& p2);
00156 };
00157 
00163 class CS_CSGEOM_EXPORT csIntersect2
00164 {
00165 public:
00172   static bool PlanePolygon (const csPlane2& plane, csPoly2D* poly,
00173         csSegment2& segment);
00174 
00180   static bool SegmentSegment (
00181     const csSegment2& a, const csSegment2& b,   // Two segments.
00182     csVector2& isect, float& dist);         // intersection point and distance
00183 
00189   static bool SegmentLine (
00190     const csSegment2& a,                // First segment.
00191     const csSegment2& b,                // A line (end is only direction)
00192     csVector2& isect, float& dist);     // intersection point and distance
00193 
00198   static bool LineLine (
00199     // Two lines (end is only direction).
00200     const csSegment2& a, const csSegment2& b,
00201     csVector2& isect);                      // intersection point
00202 
00211   static bool SegmentPlane (
00212     const csVector2& u, const csVector2& v,
00213     const csPlane2& p,                     // plane Ax+By+Cz+D=0
00214     csVector2& isect,                     // intersection point
00215     float& dist);                       // distance from u to isect
00216 
00225   static bool SegmentPlane (
00226     const csSegment2& uv,       // Segment.
00227     const csPlane2& p,                     // plane Ax+By+Cz+D=0
00228     csVector2& isect,                     // intersection point
00229     float& dist)                        // distance from u to isect
00230   {
00231     return SegmentPlane (uv.Start (), uv.End (), p, isect, dist);
00232   }
00233 
00238   static void SegmentPlaneNoTest (const csVector2& u, const csVector2& v,
00239                      const csPlane2& p, csVector2& isect, float& dist)
00240   {
00241     float x,y, denom;
00242     x = v.x-u.x;  y = v.y-u.y;
00243     denom = p.norm.x*x + p.norm.y*y;
00244     dist = -(p.norm*u + p.CC) / denom;
00245     isect.x = u.x + dist*x;  isect.y = u.y + dist*y;
00246   }
00247 
00252   static void SegmentPlaneNoTest (const csSegment2& uv,
00253                      const csPlane2& p, csVector2& isect, float& dist)
00254   {
00255     SegmentPlaneNoTest (uv.Start (), uv.End (), p, isect, dist);
00256   }
00257 
00263   static bool PlanePlane (const csPlane2& p1, const csPlane2& p2,
00264                       csVector2& isect);
00265 
00266 };
00267 
00270 #endif // __CS_MATH2D_H__

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