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.

10 files changed, 48 insertions, 7 deletions

diff --git a/extern/bullet2/src/BulletDynamics/ConstraintSolver/btContactSolverInfo.h b/extern/bullet2/src/BulletDynamics/ConstraintSolver/btContactSolverInfo.h
index e99430c00de..a11fc94ea11 100644
--- a/extern/bullet2/src/BulletDynamics/ConstraintSolver/btContactSolverInfo.h
+++ b/extern/bullet2/src/BulletDynamics/ConstraintSolver/btContactSolverInfo.h
@@ -77,7 +77,7 @@ struct btContactSolverInfo : public btContactSolverInfoData
 		m_splitImpulsePenetrationThreshold = -0.02f;
 		m_linearSlop = btScalar(0.0);
 		m_warmstartingFactor=btScalar(0.85);
-		m_solverMode = SOLVER_USE_WARMSTARTING | SOLVER_SIMD ;//SOLVER_RANDMIZE_ORDER
+		m_solverMode = SOLVER_USE_WARMSTARTING | SOLVER_USE_2_FRICTION_DIRECTIONS |SOLVER_SIMD | SOLVER_RANDMIZE_ORDER;
 		m_restingContactRestitutionThreshold = 2;//resting contact lifetime threshold to disable restitution
 	}
 };
diff --git a/source/blender/blenkernel/intern/object.c b/source/blender/blenkernel/intern/object.c
index bffbcf73672..9739668c7c7 100644
--- a/source/blender/blenkernel/intern/object.c
+++ b/source/blender/blenkernel/intern/object.c
@@ -984,6 +984,8 @@ Object *add_only_object(int type, char *name)
 	ob->anisotropicFriction[2] = 1.0f;
 	ob->gameflag= OB_PROP|OB_COLLISION;
 	ob->margin = 0.0;
+	/* ob->pad3 == Contact Processing Threshold */
+	ob->pad3 = 1.;
 	
 	/* NT fluid sim defaults */
 	ob->fluidsimFlag = 0;
diff --git a/source/blender/blenloader/intern/readfile.c b/source/blender/blenloader/intern/readfile.c
index bda0348f2ca..0b0a97b7ec0 100644
--- a/source/blender/blenloader/intern/readfile.c
+++ b/source/blender/blenloader/intern/readfile.c
@@ -8083,7 +8083,7 @@ static void do_versions(FileData *fd, Library *lib, Main *main)
 		/* Adjustments needed after Bullets update */
 		for(ob = main->object.first; ob; ob= ob->id.next) {
 			ob->damping *= 0.635f;
-			ob->rdamping = 0.1 + (0.59f * ob->rdamping);
+			ob->rdamping = 0.1 + (0.8f * ob->rdamping);
 		}
 	}
 	
@@ -8105,11 +8105,12 @@ static void do_versions(FileData *fd, Library *lib, Main *main)
 			wrld->occlusionRes = 128;
 		}
 	}
-		
+
 	if (main->versionfile < 248 || (main->versionfile == 248 && main->subversionfile < 5)) {
 		Object *ob;
 		World *wrld;
 		for(ob = main->object.first; ob; ob= ob->id.next) {
+			ob->pad3 = 1.; //pad3 is used for m_contactProcessingThreshold
 			if(ob->parent) {
 				/* check if top parent has compound shape set and if yes, set this object
 				   to compound shaper as well (was the behaviour before, now it's optional) */
diff --git a/source/blender/makesdna/DNA_object_types.h b/source/blender/makesdna/DNA_object_types.h
index 9121f38be16..11fa44fe488 100644
--- a/source/blender/makesdna/DNA_object_types.h
+++ b/source/blender/makesdna/DNA_object_types.h
@@ -159,7 +159,7 @@ typedef struct Object {
 	float margin;
 	float max_vel; /* clamp the maximum velocity 0.0 is disabled */
 	float min_vel; /* clamp the maximum velocity 0.0 is disabled */
-	float pad3; /* clamp the maximum velocity 0.0 is disabled */
+	float pad3; /* pad3 is now used for m_contactProcessingThreshold, can we still rename it? */
 
 	char dt, dtx;
 	char totcol;	/* copy of mesh or curve or meta */
diff --git a/source/blender/src/buttons_logic.c b/source/blender/src/buttons_logic.c
index b7039673dfc..b0ce3c8a95b 100644
--- a/source/blender/src/buttons_logic.c
+++ b/source/blender/src/buttons_logic.c
@@ -3198,11 +3198,17 @@ static uiBlock *advanced_bullet_menu(void *arg_ob)
 			uiDefButF(block, NUM, 0, "Margin", 
 					xco, yco, 180, 19, &ob->margin, 0.001, 1.0, 1, 0, 
 					"Collision margin");
+
 			
-			yco -= 20;
 
 			if (ob->gameflag & OB_RIGID_BODY)
 			{
+				uiDefButF(block, NUM, 0, "CPT",
+					xco+180, yco, 180, 19, &ob->pad3, 0.00, 1., 1, 0, 
+					"Contact Processing Threshold");
+			
+				yco -= 20;
+
 				uiDefButBitI(block, TOG, OB_LOCK_RIGID_BODY_X_AXIS, 0, "Lock X Axis", 
 					xco, yco, 180, 19, &ob->gameflag2, 0, 0, 0, 0, 
 					"Disable simulation of linear motion along the X axis");
@@ -3226,8 +3232,9 @@ static uiBlock *advanced_bullet_menu(void *arg_ob)
 				uiDefButBitI(block, TOG, OB_LOCK_RIGID_BODY_Z_ROT_AXIS, 0, "Lock Z Rot Axis", 
 					xco+=180, yco, 180, 19, &ob->gameflag2, 0, 0, 0, 0, 
 					"Disable simulation of angular motion along the Z axis");
-				yco -= 20;
 			}
+
+			yco -= 20;
 			xco = 0;
 			
 			uiBlockEndAlign(block);
@@ -3279,6 +3286,10 @@ static uiBlock *advanced_bullet_menu(void *arg_ob)
 			uiDefButF(block, NUM, 0, "Margin", 
 					xco, yco, 180, 19, &ob->margin, 0.0, 1.0, 1, 0, 
 					"Collision margin");
+			uiDefButF(block, NUM, 0, "CPT",
+				xco+180, yco, 180, 19, &ob->pad3, 0.00, 1., 1, 0, 
+				"Contact Processing Threshold");
+
 		}
 		yco -= 20;
 		xco = 0;
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]
 
 };