boxcollision.cpp

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#include <boxcollision.h>


//
// Crap code to do specific job.
// If I were not so flat this would be generalized to
// reflect of an arbitary line, reducing the size of code.
// 
// Also in this case the rectangular coordinates are the natural
// solution, the first method may take much more computing.

//
// The important stuff is the condition and solution
//  x0+r<x then ok, else step back and solve intersection.
//  x + t1.v = x0+r
//  
boolc boxcollision::left( particle & p, doublec h ) const
{
  assert(h>0.0);

  if ( x0 < p.pos[0]-p.radius )
    return false;

  p.step(-h);

  assert(p.vel[0]!=0.0);
  doublec t1 = 
    (x0+p.radius-p.pos[0])/p.vel[0];
  doublec t2 = h-t1;

  p.step(t1-h);

  p.vel[0]*=-1.0;
  p.step(t2);

  return true;
}

boolc boxcollision::right( particle & p, doublec h ) const
{
  assert(h>0.0);

  if ( p.pos[0] < x1-p.radius )
    return false;

  p.step(-h);

  assert(p.vel[0]!=0.0);
  doublec t1 = 
    (x1-p.radius-p.pos[0])/p.vel[0];
  doublec t2 = h-t1;

  p.step(t1-h);

  p.vel[0]*=-1.0;
  p.step(t2);

  return true;
}

boolc boxcollision::up( particle & p, doublec h ) const
{
  assert(h>0.0);

  if ( p.pos[1] < y1-p.radius )
    return false;

  p.step(-h);

  assert(p.vel[1]!=0.0);
  doublec t1 = 
    (y1-p.radius-p.pos[1])/p.vel[1];
  doublec t2 = h-t1;

  p.step(t1-h);

  p.vel[1]*=-1.0;
  p.step(t2);

  return true;
}

boolc boxcollision::down( particle & p, doublec h ) const
{
  assert(h>0.0);

  if ( y0+p.radius < p.pos[1] )
    return false;

  p.step(-h);

  assert(p.vel[1]!=0.0);
  doublec t1 = 
    (y0+p.radius-p.pos[1])/p.vel[1];
  doublec t2 = h-t1;

#ifdef DEGUG_BOX
if ((t1>0.0)==false)
{
  cout << SHOW(t1) << " " << SHOW(t2) << " " << SHOW(h) << endl;
}
#endif

  p.step(t1-h);

  p.vel[1]*=-1.0;
  p.step(t2);

  return true;
}

ostream & operator <<
(
  ostream & os,
  boxcollision const & b
)
{ 
  return b.print(os); 
}