Set default constraint solver mode more compatible to Blender 2.48 settings, this fixes rigid body stacking in this blend file:

http://blenderartists.org/forum/showpost.php?p=1382653&postcount=102

(todo: expose this setting in World setting GUI)

Expose contact processing threshold in Advanced GUI, next to rigid body margin, called CPT.
Default to 1, makes rigid body stacking a bit more stable, smaller values makes sliding easier (at the cost of easier jittering).
Disabled for 'dynamic' objects that don't rotate, because characters etc. always need smooth sliding.

5 files changed, 28 insertions, 1 deletions

diff --git a/source/gameengine/Converter/BL_BlenderDataConversion.cpp b/source/gameengine/Converter/BL_BlenderDataConversion.cpp
index 06a4da4fce0..a9c839595c2 100644
--- a/source/gameengine/Converter/BL_BlenderDataConversion.cpp
+++ b/source/gameengine/Converter/BL_BlenderDataConversion.cpp
@@ -1412,11 +1412,22 @@ void BL_CreatePhysicsObjectNew(KX_GameObject* gameobj,
 	objprop.m_isCompoundChild = isCompoundChild;
 	objprop.m_hasCompoundChildren = hasCompoundChildren;
 	objprop.m_margin = blenderobject->margin;
+	
 	// ACTOR is now a separate feature
 	objprop.m_isactor = (blenderobject->gameflag & OB_ACTOR)!=0;
 	objprop.m_dyna = (blenderobject->gameflag & OB_DYNAMIC) != 0;
 	objprop.m_softbody = (blenderobject->gameflag & OB_SOFT_BODY) != 0;
 	objprop.m_angular_rigidbody = (blenderobject->gameflag & OB_RIGID_BODY) != 0;
+	
+	///contact processing threshold is only for rigid bodies and static geometry, not 'dynamic'
+	if (objprop.m_angular_rigidbody || !objprop.m_dyna )
+	{
+		objprop.m_contactProcessingThreshold = blenderobject->pad3;
+	} else
+	{
+		objprop.m_contactProcessingThreshold = 0.f;
+	}
+
 	objprop.m_sensor = (blenderobject->gameflag & OB_SENSOR) != 0;
 	
 	if (objprop.m_softbody)
@@ -1461,6 +1472,7 @@ void BL_CreatePhysicsObjectNew(KX_GameObject* gameobj,
 			objprop.m_soft_numclusteriterations= blenderobject->bsoft->numclusteriterations;	/* number of iterations to refine collision clusters*/
 			objprop.m_soft_welding = blenderobject->bsoft->welding;		/* welding */
 			objprop.m_margin = blenderobject->bsoft->margin;
+			objprop.m_contactProcessingThreshold = 0.f;
 		} else
 		{
 			objprop.m_gamesoftFlag = OB_BSB_BENDING_CONSTRAINTS | OB_BSB_SHAPE_MATCHING | OB_BSB_AERO_VPOINT;
@@ -1501,6 +1513,7 @@ void BL_CreatePhysicsObjectNew(KX_GameObject* gameobj,
 			objprop.m_soft_numclusteriterations= 16;
 			objprop.m_soft_welding = 0.f;
 			objprop.m_margin = 0.f;
+			objprop.m_contactProcessingThreshold = 0.f;
 		}
 	}
 
diff --git a/source/gameengine/Ketsji/KX_ConvertPhysicsObject.h b/source/gameengine/Ketsji/KX_ConvertPhysicsObject.h
index e48fddb30bd..74042366bae 100644
--- a/source/gameengine/Ketsji/KX_ConvertPhysicsObject.h
+++ b/source/gameengine/Ketsji/KX_ConvertPhysicsObject.h
@@ -139,6 +139,8 @@ struct KX_ObjectProperties
 
 	/////////////////////////
 	double  m_margin;
+	float	m_contactProcessingThreshold;
+
 	KX_BoundBoxClass	m_boundclass;
 	union {
 		KX_BoxBounds	box;
diff --git a/source/gameengine/Ketsji/KX_ConvertPhysicsObjects.cpp b/source/gameengine/Ketsji/KX_ConvertPhysicsObjects.cpp
index 76642649afc..cdba59dd9ca 100644
--- a/source/gameengine/Ketsji/KX_ConvertPhysicsObjects.cpp
+++ b/source/gameengine/Ketsji/KX_ConvertPhysicsObjects.cpp
@@ -1103,6 +1103,8 @@ void	KX_ConvertBulletObject(	class	KX_GameObject* gameobj,
 		(isbulletdyna) ? short(CcdConstructionInfo::AllFilter) : 
 		short(CcdConstructionInfo::AllFilter ^ CcdConstructionInfo::StaticFilter);
 	ci.m_bRigid = objprop->m_dyna && objprop->m_angular_rigidbody;
+	
+	ci.m_contactProcessingThreshold = objprop->m_contactProcessingThreshold;//todo: expose this in advanced settings, just like margin, default to 10000 or so
 	ci.m_bSoft = objprop->m_softbody;
 	ci.m_bSensor = isbulletsensor;
 	MT_Vector3 scaling = gameobj->NodeGetWorldScaling();
diff --git a/source/gameengine/Physics/Bullet/CcdPhysicsController.cpp b/source/gameengine/Physics/Bullet/CcdPhysicsController.cpp
index 6b00011b693..710d0656f6d 100644
--- a/source/gameengine/Physics/Bullet/CcdPhysicsController.cpp
+++ b/source/gameengine/Physics/Bullet/CcdPhysicsController.cpp
@@ -519,6 +519,8 @@ void CcdPhysicsController::CreateRigidbody()
 		{
 			body->setAngularFactor(0.f);
 		}
+		body->setContactProcessingThreshold(m_cci.m_contactProcessingThreshold);
+
 	}
 	if (m_object && m_cci.m_do_anisotropic)
 	{
diff --git a/source/gameengine/Physics/Bullet/CcdPhysicsController.h b/source/gameengine/Physics/Bullet/CcdPhysicsController.h
index fc8de0e2ded..d73759bac76 100644
--- a/source/gameengine/Physics/Bullet/CcdPhysicsController.h
+++ b/source/gameengine/Physics/Bullet/CcdPhysicsController.h
@@ -231,7 +231,8 @@ struct CcdConstructionInfo
 		m_physicsEnv(0),
 		m_inertiaFactor(1.f),
 		m_do_anisotropic(false),
-		m_anisotropicFriction(1.f,1.f,1.f)
+		m_anisotropicFriction(1.f,1.f,1.f),
+		m_contactProcessingThreshold(1e10)
 	{
 	}
 
@@ -317,6 +318,13 @@ struct CcdConstructionInfo
 	btScalar	m_fh_distance;           ///< The range above the surface where Fh is active.    
 	bool		m_fh_normal;             ///< Should the object slide off slopes?
 	float		m_radius;//for fh backwards compatibility
+	
+	///m_contactProcessingThreshold allows to process contact points with positive distance
+	///normally only contacts with negative distance (penetration) are solved
+	///however, rigid body stacking is more stable when positive contacts are still passed into the constraint solver
+	///this might sometimes lead to collisions with 'internal edges' such as a sliding character controller
+	///so disable/set m_contactProcessingThreshold to zero for sliding characters etc.
+	float		m_contactProcessingThreshold;///< Process contacts with positive distance in range [0..INF]
 
 };