From 59d5a3dc1ebea1aa8bc6b78eef06d1d17d9fd30e Mon Sep 17 00:00:00 2001
From: Robin Engman <robinengman@hotmail.com>
Date: Thu, 19 Dec 2013 10:15:32 +0100
Subject: [PATCH] Created function for friction

---
 .../Implementation/PhysicsAPI_Impl.cpp        | 31 +++----------------
 Code/GamePhysics/PhysicsFormula-Impl.h        | 28 +++++++++++++++++
 Code/GamePhysics/PhysicsFormula.h             |  7 +++++
 3 files changed, 40 insertions(+), 26 deletions(-)

diff --git a/Code/GamePhysics/Implementation/PhysicsAPI_Impl.cpp b/Code/GamePhysics/Implementation/PhysicsAPI_Impl.cpp
index 9ede391d..9d30a7e4 100644
--- a/Code/GamePhysics/Implementation/PhysicsAPI_Impl.cpp
+++ b/Code/GamePhysics/Implementation/PhysicsAPI_Impl.cpp
@@ -7,6 +7,7 @@ using namespace ::Oyster::Physics;
 using namespace ::Oyster::Math;
 using namespace ::Oyster::Collision3D;
 using namespace ::Utility::DynamicMemory;
+using namespace ::Utility::Value;
 
 API_Impl API_instance;
 
@@ -43,32 +44,10 @@ namespace
 																				protoState.GetMass(), protoG_Magnitude );;
 					Float4 sumJ = normal*impulse;
 					
-					// FRICTION
-					// Relative momentum after normal impulse
-					Float4 relativeMomentum = deuterState.GetLinearMomentum() - protoState.GetLinearMomentum();
-
-					Float4 tanFriction = relativeMomentum - relativeMomentum.Dot(normal)*normal;
-					tanFriction.Normalize();
-
-					Float magnitudeFriction =  -relativeMomentum.Dot(tanFriction);
-					magnitudeFriction = magnitudeFriction/( 1/protoState.GetMass() + 1/deuterState.GetMass() );
-
-					float mu = 0.5f;
- 
-					Float4 frictionImpulse;
-					if( abs(magnitudeFriction) < impulse*mu )
-					{
-						frictionImpulse = magnitudeFriction*tanFriction;
-					}
-					else
-					{
-					  Float dynamicFriction = 0.5f;
-					  frictionImpulse = -impulse*tanFriction*dynamicFriction;
-					}
- 
-					// Apply
-					sumJ -= ( 1 / protoState.GetMass() )*frictionImpulse;
-					// FRICTION END
+					sumJ -= Formula::CollisionResponse::Friction( impulse, normal, protoState.GetLinearMomentum(), 
+																	protoState.GetFrictionCoeff(), 0.2f, protoState.GetMass(), 
+																	deuterState.GetLinearMomentum(), deuterState.GetFrictionCoeff(), 
+																	0.2f, deuterState.GetMass());
 
 					// calc from perspective of proto
 					proto->GetNormalAt( worldPointOfContact, normal );
diff --git a/Code/GamePhysics/PhysicsFormula-Impl.h b/Code/GamePhysics/PhysicsFormula-Impl.h
index c0d4ed64..4cb7b5ef 100644
--- a/Code/GamePhysics/PhysicsFormula-Impl.h
+++ b/Code/GamePhysics/PhysicsFormula-Impl.h
@@ -40,6 +40,34 @@ namespace Oyster { namespace Physics { namespace Formula
 		{
 			return (e + 1) * (mB*gA - mA*gB) / (mA + mB);
 		}
+
+		inline ::Oyster::Math::Float4 Friction( ::Oyster::Math::Float i, ::Oyster::Math::Float4 iN, ::Oyster::Math::Float4 momA, ::Oyster::Math::Float sFA, ::Oyster::Math::Float dFA, ::Oyster::Math::Float mA, ::Oyster::Math::Float4 momB, ::Oyster::Math::Float sFB, ::Oyster::Math::Float dFB, ::Oyster::Math::Float mB )
+		{
+			// FRICTION
+			// Relative momentum after normal impulse
+			::Oyster::Math::Float4 relativeMomentum = momB - momA;
+
+			::Oyster::Math::Float4 tanFriction = relativeMomentum - relativeMomentum.Dot( iN )*iN;
+			tanFriction.Normalize();
+
+			::Oyster::Math::Float magnitudeFriction = -relativeMomentum.Dot( tanFriction );
+			magnitudeFriction = magnitudeFriction*mA*mB/( mA + mB );
+
+			::Oyster::Math::Float mu = 0.5f*( sFA + sFB );
+ 
+			::Oyster::Math::Float4 frictionImpulse;
+			if( abs(magnitudeFriction) < i*mu )
+			{
+				frictionImpulse = magnitudeFriction*tanFriction;
+			}
+			else
+			{
+				::Oyster::Math::Float dynamicFriction = 0.5f*( dFA + dFB );
+				frictionImpulse = -i*tanFriction*dynamicFriction;
+			}
+ 
+			return ( 1 / mA )*frictionImpulse;
+		}
 	}
 
 } } }
diff --git a/Code/GamePhysics/PhysicsFormula.h b/Code/GamePhysics/PhysicsFormula.h
index c15d8078..a8fea658 100644
--- a/Code/GamePhysics/PhysicsFormula.h
+++ b/Code/GamePhysics/PhysicsFormula.h
@@ -20,6 +20,13 @@ namespace Oyster { namespace Physics { namespace Formula
 		::Oyster::Math::Float Impulse( ::Oyster::Math::Float coeffOfRestitution,
 									   ::Oyster::Math::Float massA, ::Oyster::Math::Float momentumA,
 									   ::Oyster::Math::Float massB, ::Oyster::Math::Float momentumB );
+
+		::Oyster::Math::Float4 Friction( ::Oyster::Math::Float impulse, ::Oyster::Math::Float4 impulseNormal, 
+										 ::Oyster::Math::Float4 momentumA, ::Oyster::Math::Float staticFrictionA, 
+										 ::Oyster::Math::Float dynamicFrictionA, ::Oyster::Math::Float massA, 
+										 ::Oyster::Math::Float4 momentumB, ::Oyster::Math::Float staticFrictionB, 
+										 ::Oyster::Math::Float dynamicFrictionB, ::Oyster::Math::Float massB );
+		
 	}
 } } }