Major Bug Fixes

- Several fixes to BeginContact and EndContact
- Makes fixture<->particle collision distance use radius instead of diameter
- Makes b2ParticleSystem forces clear in b2World::ClearForces()
- Fixes elastic directional bias

Author: Manamongods

liquidfun/Box2D/Box2D/Common/b2Settings.h

@@ -82,10 +82,12 @@ typedef unsigned long long uint64;
 #endif
 #endif
 
+
 /// @file
 /// Global tuning constants based on meters-kilograms-seconds (MKS) units.
 ///
 
+
 // Collision
 
 /// The maximum number of contact points between two convex shapes. Do
@@ -196,6 +198,14 @@ typedef unsigned long long uint64;
 /// The time into the future that collisions against barrier particles will be detected.
 #define b2_barrierCollisionTime 2.5f
 
+/// Multiplier for the radius of a particle when colliding with a fixture.
+/// Originally the diameter was used, so a multiplier of 2 would restore that behaviour.
+#define b2_fixtureParticleCollisionRadiusScaler 1
+
+/// Prevents directional bias when solving elastic triads
+#define b2_elasticPreserveVelocity
+
+
 // Sleep
 
 /// The time that a body must be still before it will go to sleep.
@@ -207,6 +217,7 @@ typedef unsigned long long uint64;
 /// A body cannot sleep if its angular velocity is above this tolerance.
 #define b2_angularSleepTolerance	(2.0f / 180.0f * b2_pi)
 
+
 // Memory Allocation
 
 /// Implement this function to use your own memory allocator.
@@ -236,9 +247,11 @@ void b2SetNumAllocs(const int32 numAllocs);
 /// Get number of calls to b2Alloc minus number of calls to b2Free.
 int32 b2GetNumAllocs();
 
+
 /// Logging function.
 void b2Log(const char* string, ...);
 
+
 /// Version numbering scheme.
 /// See http://en.wikipedia.org/wiki/Software_versioning
 struct b2Version

liquidfun/Box2D/Box2D/Dynamics/b2World.cpp

@@ -1057,6 +1057,11 @@ void b2World::ClearForces()
 		body->m_force.SetZero();
 		body->m_torque = 0.0f;
 	}
+
+	for (b2ParticleSystem* p = m_particleSystemList; p; p = p->GetNext())
+	{
+		p->m_hasForce = false;
+	}
 }
 
 struct b2WorldQueryWrapper