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csgeom/math2d.h

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/*
    Copyright (C) 1998-2000 by Jorrit Tyberghein
    Largely rewritten by Ivan Avramovic <[email protected]>

    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Library General Public
    License as published by the Free Software Foundation; either
    version 2 of the License, or (at your option) any later version.

    This library is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
    Library General Public License for more details.

    You should have received a copy of the GNU Library General Public
    License along with this library; if not, write to the Free
    Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/

#ifndef __CS_MATH2D_H__
#define __CS_MATH2D_H__

#include "csextern.h"

#include "csgeom/plane2.h"
#include "csgeom/segment.h"
#include "csgeom/vector2.h"

class csBox2;
class csPoly2D;

class CS_CRYSTALSPACE_EXPORT csMath2
{
public:
  static int WhichSide2D (const csVector2& v,
                          const csVector2& s1, const csVector2& s2)
  {
    float k  = (s1.y - v.y)*(s2.x - s1.x);
    float k1 = (s1.x - v.x)*(s2.y - s1.y);
    if (k < k1) return -1;
    else if (k > k1) return 1;
    else return 0;
  }

  static int WhichSide2D (const csVector2& v,
                          const csSegment2& s)
  {
    return WhichSide2D (v, s.Start (), s.End ());
  }

  static int InPoly2D (const csVector2& v,
                       csVector2* P, int n, csBox2* bounding_box);

  static float Area2 (const csVector2& a,
                      const csVector2& b,
                      const csVector2& c)
  {
    return
      a.x * b.y - a.y * b.x +
      a.y * c.x - a.x * c.y +
      b.x * c.y - c.x * b.y;
  }

  static float Right (const csVector2& a,
                      const csVector2& b,
                      const csVector2& c)
  {
    return Area2 (a, b, c) <= -SMALL_EPSILON;
  }

  static float Left (const csVector2& a,
                     const csVector2& b,
                     const csVector2& c)
  {
    return Area2 (a, b, c) >= SMALL_EPSILON;
  }

  static bool Visible (const csVector2& p, const csPlane2& pl)
  { return pl.Classify (p) <= 0; }

  static bool PlanesEqual (const csPlane2& p1, const csPlane2& p2)
  {
    return ( ( p1.norm - p2.norm) < (float).001 ) &&
             (  ABS (p1.CC-p2.CC) < (float).001 );
  }

  static bool PlanesClose (const csPlane2& p1, const csPlane2& p2);
};

class CS_CRYSTALSPACE_EXPORT csIntersect2
{
public:
  static bool PlanePolygon (const csPlane2& plane, csPoly2D* poly,
        csSegment2& segment);

  static bool SegmentSegment (
    const csSegment2& a, const csSegment2& b,   // Two segments.
    csVector2& isect, float& dist);         // intersection point and distance

  static bool SegmentLine (
    const csSegment2& a,                // First segment.
    const csSegment2& b,                // A line (end is only direction)
    csVector2& isect, float& dist);     // intersection point and distance

  static bool LineLine (
    // Two lines (end is only direction).
    const csSegment2& a, const csSegment2& b,
    csVector2& isect);                      // intersection point

  static bool SegmentPlane (
    const csVector2& u, const csVector2& v,
    const csPlane2& p,                     // plane Ax+By+Cz+D=0
    csVector2& isect,                     // intersection point
    float& dist);                       // distance from u to isect

  static bool SegmentPlane (
    const csSegment2& uv,       // Segment.
    const csPlane2& p,                     // plane Ax+By+Cz+D=0
    csVector2& isect,                     // intersection point
    float& dist)                        // distance from u to isect
  {
    return SegmentPlane (uv.Start (), uv.End (), p, isect, dist);
  }

  static void SegmentPlaneNoTest (const csVector2& u, const csVector2& v,
                     const csPlane2& p, csVector2& isect, float& dist)
  {
    float x,y, denom;
    x = v.x-u.x;  y = v.y-u.y;
    denom = p.norm.x*x + p.norm.y*y;
    dist = -(p.norm*u + p.CC) / denom;
    isect.x = u.x + dist*x;  isect.y = u.y + dist*y;
  }

  static void SegmentPlaneNoTest (const csSegment2& uv,
                     const csPlane2& p, csVector2& isect, float& dist)
  {
    SegmentPlaneNoTest (uv.Start (), uv.End (), p, isect, dist);
  }

  static bool PlanePlane (const csPlane2& p1, const csPlane2& p2,
                      csVector2& isect);

};

#endif // __CS_MATH2D_H__

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