text: /* Copyright (c) 2007 Scott Lembcke
   * 
   * Permission is hereby granted, free of charge, to any person obtaining a copy
   * of this software and associated documentation files (the "Software"), to deal
   * in the Software without restriction, including without limitation the rights
   * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
   * copies of the Software, and to permit persons to whom the Software is
   * furnished to do so, subject to the following conditions:
   * 
   * The above copyright notice and this permission notice shall be included in
   * all copies or substantial portions of the Software.
   * 
   * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
   * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
   * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
   * SOFTWARE.
   */
  
  // Determines how fast penetrations resolve themselves.
  extern cpFloat cp_bias_coef;
  // Amount of allowed penetration. Used to reduce vibrating contacts.
  extern cpFloat cp_collision_slop;
  
  // Data structure for contact points.
  typedef struct cpContact{
  	// Contact point and normal.
  	cpVect p, n;
  	// Penetration distance.
  	cpFloat dist;
  	
  	// Calculated by cpArbiterPreStep().
  	cpVect r1, r2;
  	cpFloat nMass, tMass, bounce;
  
  	// Persistant contact information.
  	cpFloat jnAcc, jtAcc, jBias;
  	cpFloat bias;
  	
  	// Hash value used to (mostly) uniquely identify a contact.
  	unsigned int hash;
  } cpContact;
  
  // Contacts are always allocated in groups.
  cpContact* cpContactInit(cpContact *con, cpVect p, cpVect n, cpFloat dist, unsigned int hash);
  
  // Sum the contact impulses. (Can be used after cpSpaceStep() returns)
  cpVect cpContactsSumImpulses(cpContact *contacts, int numContacts);
  cpVect cpContactsSumImpulsesWithFriction(cpContact *contacts, int numContacts);
  
  // Data structure for tracking collisions between shapes.
  typedef struct cpArbiter{
  	// Information on the contact points between the objects.
  	int numContacts;
  	cpContact *contacts;
  	
  	// The two shapes involved in the collision.
  	cpShape *a, *b;
  	
  	// Calculated by cpArbiterPreStep().
  	cpFloat u;
  	cpVect target_v;
  	
  	// Time stamp of the arbiter. (from cpSpace)
  	int stamp;
  } cpArbiter;
  
  // Basic allocation/destruction functions.
  cpArbiter* cpArbiterAlloc(void);
  cpArbiter* cpArbiterInit(cpArbiter *arb, cpShape *a, cpShape *b, int stamp);
  cpArbiter* cpArbiterNew(cpShape *a, cpShape *b, int stamp);
  
  void cpArbiterDestroy(cpArbiter *arb);
  void cpArbiterFree(cpArbiter *arb);
  
  // These functions are all intended to be used internally.
  // Inject new contact points into the arbiter while preserving contact history.
  void cpArbiterInject(cpArbiter *arb, cpContact *contacts, int numContacts);
  // Precalculate values used by the solver.
  void cpArbiterPreStep(cpArbiter *arb, cpFloat dt_inv);
  void cpArbiterApplyCachedImpulse(cpArbiter *arb);
  // Run an iteration of the solver on the arbiter.
  void cpArbiterApplyImpulse(cpArbiter *arb, cpFloat eCoef);
  