# csgeom/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
00031 #include "csextern.h"
00032
00033 #include "csgeom/plane2.h"
00034 #include "csgeom/segment.h"
00035 #include "csgeom/vector2.h"
00036
00037 class csBox2;
00038 class csPoly2D;
00039
00044 class CS_CRYSTALSPACE_EXPORT csMath2
00045 {
00046 public:
00053   static int WhichSide2D (const csVector2& v,
00054                           const csVector2& s1, const csVector2& s2)
00055   {
00056     float k  = (s1.y - v.y)*(s2.x - s1.x);
00057     float k1 = (s1.x - v.x)*(s2.y - s1.y);
00058     if (k < k1) return -1;
00059     else if (k > k1) return 1;
00060     else return 0;
00061   }
00062
00069   static int WhichSide2D (const csVector2& v,
00070                           const csSegment2& s)
00071   {
00072     return WhichSide2D (v, s.Start (), s.End ());
00073   }
00074
00082   static int InPoly2D (const csVector2& v,
00083                        csVector2* P, int n, csBox2* bounding_box);
00084
00090   static float Area2 (const csVector2& a,
00091                       const csVector2& b,
00092                       const csVector2& c)
00093   {
00094     return
00095       a.x * b.y - a.y * b.x +
00096       a.y * c.x - a.x * c.y +
00097       b.x * c.y - c.x * b.y;
00098   }
00099
00105   static float Right (const csVector2& a,
00106                       const csVector2& b,
00107                       const csVector2& c)
00108   {
00109     return Area2 (a, b, c) <= -SMALL_EPSILON;
00110   }
00111
00117   static float Left (const csVector2& a,
00118                      const csVector2& b,
00119                      const csVector2& c)
00120   {
00121     return Area2 (a, b, c) >= SMALL_EPSILON;
00122   }
00123
00129   static bool Visible (const csVector2& p, const csPlane2& pl)
00130   { return pl.Classify (p) <= 0; }
00131
00138   static bool PlanesEqual (const csPlane2& p1, const csPlane2& p2)
00139   {
00140     return ( ( p1.norm - p2.norm) < (float).001 ) &&
00141              (  ABS (p1.CC-p2.CC) < (float).001 );
00142   }
00143
00149   static bool PlanesClose (const csPlane2& p1, const csPlane2& p2);
00150 };
00151
00157 class CS_CRYSTALSPACE_EXPORT csIntersect2
00158 {
00159 public:
00166   static bool PlanePolygon (const csPlane2& plane, csPoly2D* poly,
00167         csSegment2& segment);
00168
00175   static bool SegmentSegment (
00176     const csSegment2& a, const csSegment2& b,   // Two segments.
00177     csVector2& isect, float& dist);         // intersection point and distance
00178
00185   static bool SegmentLine (
00186     const csSegment2& a,                // First segment.
00187     const csSegment2& b,                // A line (end is only direction)
00188     csVector2& isect, float& dist);     // intersection point and distance
00189
00195   static bool LineLine (
00196     // Two lines (end is only direction).
00197     const csSegment2& a, const csSegment2& b,
00198     csVector2& isect);                      // intersection point
00199
00209   static bool SegmentPlane (
00210     const csVector2& u, const csVector2& v,
00211     const csPlane2& p,                     // plane Ax+By+Cz+D=0
00212     csVector2& isect,                     // intersection point
00213     float& dist);                       // distance from u to isect
00214
00224   static bool SegmentPlane (
00225     const csSegment2& uv,       // Segment.
00226     const csPlane2& p,                     // plane Ax+By+Cz+D=0
00227     csVector2& isect,                     // intersection point
00228     float& dist)                        // distance from u to isect
00229   {
00230     return SegmentPlane (uv.Start (), uv.End (), p, isect, dist);
00231   }
00232
00237   static void SegmentPlaneNoTest (const csVector2& u, const csVector2& v,
00238                      const csPlane2& p, csVector2& isect, float& dist)
00239   {
00240     float x,y, denom;
00241     x = v.x-u.x;  y = v.y-u.y;
00242     denom = p.norm.x*x + p.norm.y*y;
00243     dist = -(p.norm*u + p.CC) / denom;
00244     isect.x = u.x + dist*x;  isect.y = u.y + dist*y;
00245   }
00246
00251   static void SegmentPlaneNoTest (const csSegment2& uv,
00252                      const csPlane2& p, csVector2& isect, float& dist)
00253   {
00254     SegmentPlaneNoTest (uv.Start (), uv.End (), p, isect, dist);
00255   }
00256
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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