4 
void line()
{
  int x1 = 10, y1 = 10, x2 = 300, y2 = 500  , x, y;
  int dx, dy, //deltas
      e;      // decision parameter

  glClear(GL_COLOR_BUFFER_BIT);
  glColor3f( 1 ,0, 0);
  setPixel(x1, y1); //plot first point

  // difference between starting and ending points
  dx = x2 - x1;
  dy = y2 - y1;
  e = 2 * dy - dx;
  x = x1; y = y1;

  for(int k = 0; k < dx - 1; ++k)
  {
    if(e < 0)
    {
      //next pixel: (x+1, y)
      e = e + 2*dy;
    } 
    else 
    {
      //next pixel: (x+1, y+1)
      e = e + 2*dy - 2*dx;
      ++y;
    }
    ++x;
    setPixel(x, y);
  }

  glFlush();
}

はどこe = 2*dy - dxから来たのですか？なぜそれを2*dyまたはで増やすの2*dy - 2*dxですか？

4

2 に答える 2