spring.cxx

   1 //  $Id: spring.cxx,v 1.15 2003/07/27 18:46:11 grumbel Exp $
   2 //
   3 //  Construo - A wire-frame construction game
   4 //  Copyright (C) 2002 Ingo Ruhnke <grumbel@gmx.de>
   5 //
   6 //  This program is free software; you can redistribute it and/or
   7 //  modify it under the terms of the GNU General Public License
   8 //  as published by the Free Software Foundation; either version 2
   9 //  of the License, or (at your option) any later version.
  10 //
  11 //  This program is distributed in the hope that it will be useful,
  12 //  but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 //  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 //  GNU General Public License for more details.
  15 //
  16 //  You should have received a copy of the GNU General Public License
  17 //  along with this program; if not, write to the Free Software
  18 //  Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
  19
  20 #include "colors.hxx"
  21 #include "construo_error.hxx"
  22 #include "particle_factory.hxx"
  23 #include "spring.hxx"
  24
  25 Spring::Spring (Particle* f, Particle* s, float l)
  26 {
  27   particles.first  = f;
  28   particles.second = s;
  29   destroyed        = false;
  30   length           = l;
  31
  32   stiffness   = 50.0f;
  33   damping     = .1f;
  34   max_stretch = 0.15f;
  35
  36   f->spring_links += 1;
  37   s->spring_links += 1;
  38 }
  39
  40 Spring::Spring (Particle* f, Particle* s)
  41 {
  42   particles.first  = f;
  43   particles.second = s;
  44   destroyed        = false;
  45   length           = fabs((f->pos - s->pos).norm ());
  46
  47   stiffness   = 50.0f;
  48   damping     = .1f;
  49   max_stretch = 0.15f;
  50
  51   f->spring_links += 1;
  52   s->spring_links += 1;
  53
  54   assert (length != 0);
  55 }
  56
  57 Spring::Spring (World* world, lisp_object_t* cursor)
  58   : destroyed (false)
  59 {
  60   cursor = lisp_cdr(cursor); // Skip the identifer
  61
  62   int first_id = -1;
  63   int second_id = -1;
  64   length = -1;
  65
  66   stiffness   = 50.0f;
  67   damping     = .1f;
  68   max_stretch = 0.15f;
  69
  70   LispReader reader(cursor);
  71   reader.read_int ("first", &first_id);
  72   reader.read_int ("second", &second_id);
  73   reader.read_float ("length", &length);
  74   reader.read_float ("stiffness",   &stiffness);
  75   reader.read_float ("damping",     &damping);
  76   reader.read_float ("maxstretch", &max_stretch);
  77
  78   particles.first  = world->get_particle_mgr()->lookup_particle (first_id);
  79   particles.second = world->get_particle_mgr()->lookup_particle (second_id);
  80
  81   if (particles.first == 0 || particles.second == 0)
  82     {
  83       throw ConstruoError ("Spring: Pair lookup failed");
  84     }
  85
  86   particles.first->spring_links  += 1;
  87   particles.second->spring_links += 1;
  88
  89   if (length == -1)
  90     {
  91       //std::cout << "Spring: length missing in data file, recalculating" << std::endl;
  92       length = fabs((particles.first->pos - particles.second->pos).norm ());
  93     }
  94 }
  95
  96 Spring::~Spring ()
  97 {
  98   particles.first->spring_links -= 1;
  99   particles.second->spring_links -= 1;
 100 }
 101
 102 void
 103 Spring::update (float delta)
 104 {
 105   Vector2d dist = particles.first->pos - particles.second->pos;
 106
 107   // Calculate the stretchness of the spring, 0.0 if unstretch, else
 108   // <> 0
 109   float stretch = (dist.norm () - length);
 110
 111   //std::cout << "Stretch: " << stretch << std::endl;
 112   if (fabs(stretch/length) > max_stretch &&
 113       length > 10.0f) // atomar spring
 114     { // If the spring is streched above limits, let it get destroyed
 115       destroyed = true;
 116     }
 117   else
 118     {
 119       stretch *= stiffness;
 120       float dterm = (dist.dot(particles.first->velocity - particles.second->velocity) * damping)/dist.norm ();
 121
 122       dist.normalize ();
 123       Vector2d force = dist * (stretch + dterm);
 124
 125       /*std::cout << "DTerm: " << dterm << " HTerm: " << stretch
 126                 << " Force: " << force
 127                 << std::endl;*/
 128
 129       particles.first->add_force (-force);
 130       particles.second->add_force (force);
 131     }
 132 }
 133
 134 void
 135 Spring::draw (ZoomGraphicContext* gc)
 136 {
 137   Vector2d dist = particles.first->pos - particles.second->pos;
 138   float stretch = fabs(dist.norm ()/length - 1.0f) * 10.0f;
 139
 140   float color = fabs((stretch/max_stretch));
 141
 142   if (particles.first->pos.y  < 598.5f
 143       ||
 144       particles.second->pos.y < 598.5f)
 145     {
 146       gc->GraphicContext::draw_line(particles.first->pos,
 147                                     particles.second->pos,
 148                                     Color(color, 1.0f - color, 0.0f),
 149                                     2);
 150     }
 151 }
 152
 153 void
 154 Spring::draw_highlight (ZoomGraphicContext* gc)
 155 {
 156   gc->GraphicContext::draw_line (particles.first->pos, particles.second->pos,
 157                                  Colors::highlight, 4);
 158 }
 159
 160
 161 lisp_object_t*
 162 Spring::serialize()
 163 {
 164   LispWriter obj ("spring");
 165   obj.write_int ("first", particles.first->get_id());
 166   obj.write_int ("second", particles.second->get_id());
 167   obj.write_float ("length", length);
 168   obj.write_float ("stiffness",   stiffness);
 169   obj.write_float ("damping",     damping);
 170   obj.write_float ("maxstretch", max_stretch);
 171
 172   return obj.create_lisp ();
 173 }
 174
 175 void
 176 Spring::recalc_length ()
 177 {
 178   length = fabs((particles.first->pos - particles.second->pos).norm ());
 179 }
 180
 181 /* EOF */