UPBGE: Implement physics constraint breaking.

Bullet support an attribute for breaking impulse threshold in its
constraints (btTypedConstraint). This attribute allow bullet to
disable the constraint when the impulse is greater than the threshold
specified, when this happen the constraint function isEnabled return
false and no object are influenced by the constraint, but this constraint
still remains in dynamic world.
To renable it, the function setEnabled have to be called with true
as argument. Note that the constrained objects must be unslept.

The threshold and the enabled status are both exposed to user in the
python API under KX_ConstraintWrapper.breakingThreshold and
KX_ConstraintWrapper.enabled.

In UI the threshold is exposed in the rigid body constraint layout,
to modify this value the option "Use Breaking" must be enabled because
internally the threshold is near to infinite and it will request to show
infinite value in UI if there's no option and the user will not be able
to disable temporary breaking without lose his previous value.

Fix a part of issue: #511.

Author: panzergame

doc/python_api/rst/bge_types/bge.types.KX_ConstraintWrapper.rst

@@ -141,3 +141,14 @@ base class --- :class:`PyObjectPlus`
          - :class:`~bge.constraints.VEHICLE_CONSTRAINT`
          - :class:`~bge.constraints.GENERIC_6DOF_CONSTRAINT`
 
+   .. attribute:: breakingThreshold
+
+      The impulse threshold breaking the constraint, if the constraint is broken :data:`enabled` is set to `False`.
+
+      :type: float greater or equal to 0
+
+   .. attribute:: enabled
+
+      The status of the constraint. Set to `True` to restore a constraint after breaking.
+
+      :type: boolean

release/scripts/startup/bl_ui/properties_constraint.py

@@ -553,6 +553,12 @@ def RIGID_BODY_JOINT(self, context, layout, con):
         row.prop(con, "use_linked_collision", text="Linked Collision")
         row.prop(con, "show_pivot", text="Display Pivot")
 
+        row = layout.row()
+        row.prop(con, "use_breaking")
+        row = row.row()
+        row.active = con.use_breaking
+        row.prop(con, "breaking_threshold")
+
         split = layout.split()
 
         col = split.column(align=True)

source/blender/makesdna/DNA_constraint_types.h

@@ -317,8 +317,7 @@ typedef struct bRigidBodyJointConstraint {
 	float       extraFz;
 	short		flag;
 	short		pad;
-	short		pad1;
-	short		pad2;
+	float breaking;
 } bRigidBodyJointConstraint;
 
 /* Clamp-To Constraint */
@@ -845,6 +844,7 @@ typedef enum eObjectSolver_Flags {
 /* Rigid-Body Constraint */
 #define CONSTRAINT_DRAW_PIVOT 0x40
 #define 	CONSTRAINT_DISABLE_LINKED_COLLISION 0x80
+#define CONSTRAINT_USE_BREAKING 0x100
 
 /* ObjectSolver Constraint -> flag */
 typedef enum eStretchTo_Flags {

source/blender/makesrna/intern/rna_constraint.c

@@ -1590,6 +1590,15 @@ static void rna_def_constraint_rigid_body_joint(BlenderRNA *brna)
 	RNA_def_property_boolean_sdna(prop, NULL, "flag", 32);
 	RNA_def_property_ui_text(prop, "Angular Z Limit", "Use minimum/maximum Z angular limit");
 	RNA_def_property_update(prop, NC_OBJECT | ND_CONSTRAINT, "rna_Constraint_update");
+
+	prop = RNA_def_property(srna, "use_breaking", PROP_BOOLEAN, PROP_NONE);
+	RNA_def_property_boolean_sdna(prop, NULL, "flag", CONSTRAINT_USE_BREAKING);
+	RNA_def_property_ui_text(prop, "Use Breaking", "Allow breaking on high impulse");
+
+	prop = RNA_def_property(srna, "breaking_threshold", PROP_FLOAT, PROP_NONE);
+	RNA_def_property_float_sdna(prop, NULL, "breaking");
+	RNA_def_property_range(prop, 0.0f, FLT_MAX);
+	RNA_def_property_ui_text(prop, "Breaking Impulse Threshold", "Break on impulse greater than threshold");
 }
 
 static void rna_def_constraint_clamp_to(BlenderRNA *brna)

source/gameengine/Ketsji/KX_ConstraintWrapper.cpp

@@ -113,6 +113,8 @@ PyMethodDef KX_ConstraintWrapper::Methods[] = {
 PyAttributeDef KX_ConstraintWrapper::Attributes[] = {
 	KX_PYATTRIBUTE_RO_FUNCTION("constraint_id", KX_ConstraintWrapper, pyattr_get_constraintId),
 	KX_PYATTRIBUTE_RO_FUNCTION("constraint_type", KX_ConstraintWrapper, pyattr_get_constraintType),
+	KX_PYATTRIBUTE_RW_FUNCTION("breakingThreshold", KX_ConstraintWrapper, pyattr_get_breakingThreshold, pyattr_set_breakingThreshold),
+	KX_PYATTRIBUTE_RW_FUNCTION("enabled", KX_ConstraintWrapper, pyattr_get_enabled, pyattr_set_enabled),
 	KX_PYATTRIBUTE_NULL	//Sentinel
 };
 
@@ -128,4 +130,44 @@ PyObject *KX_ConstraintWrapper::pyattr_get_constraintType(PyObjectPlus *self_v,
 	return PyLong_FromLong(self->m_constraint->GetType());
 }
 
+PyObject *KX_ConstraintWrapper::pyattr_get_breakingThreshold(PyObjectPlus *self_v, const KX_PYATTRIBUTE_DEF *attrdef)
+{
+	KX_ConstraintWrapper *self = static_cast<KX_ConstraintWrapper *>(self_v);
+	return PyFloat_FromDouble(self->m_constraint->GetBreakingThreshold());
+}
+
+int KX_ConstraintWrapper::pyattr_set_breakingThreshold(PyObjectPlus *self_v, const KX_PYATTRIBUTE_DEF *attrdef, PyObject *value)
+{
+	KX_ConstraintWrapper *self = static_cast<KX_ConstraintWrapper *>(self_v);
+	float val = PyFloat_AsDouble(value);
+
+	if (val == -1 && PyErr_Occurred()) {
+		PyErr_Format(PyExc_AttributeError, "constraint.%s = float: KX_ConstraintWrapper, expected a float", attrdef->m_name.c_str());
+		return PY_SET_ATTR_FAIL;
+	}
+
+	self->m_constraint->SetBreakingThreshold(val);
+	return PY_SET_ATTR_SUCCESS;
+}
+
+PyObject *KX_ConstraintWrapper::pyattr_get_enabled(PyObjectPlus *self_v, const KX_PYATTRIBUTE_DEF *attrdef)
+{
+	KX_ConstraintWrapper *self = static_cast<KX_ConstraintWrapper *>(self_v);
+	return PyBool_FromLong(self->m_constraint->GetEnabled());
+}
+
+int KX_ConstraintWrapper::pyattr_set_enabled(PyObjectPlus *self_v, const KX_PYATTRIBUTE_DEF *attrdef, PyObject *value)
+{
+	KX_ConstraintWrapper *self = static_cast<KX_ConstraintWrapper *>(self_v);
+	bool val = PyObject_IsTrue(value);
+
+	if (val == -1 && PyErr_Occurred()) {
+		PyErr_Format(PyExc_AttributeError, "constraint.%s = bool: KX_ConstraintWrapper, expected True or False", attrdef->m_name.c_str());
+		return PY_SET_ATTR_FAIL;
+	}
+
+	self->m_constraint->SetEnabled(val);
+	return PY_SET_ATTR_SUCCESS;
+}
+
 #endif // WITH_PYTHON

source/gameengine/Ketsji/KX_ConstraintWrapper.h

@@ -52,6 +52,10 @@ class	KX_ConstraintWrapper : public CValue
 
 	static PyObject *pyattr_get_constraintId(PyObjectPlus *self_v, const KX_PYATTRIBUTE_DEF *attrdef);
 	static PyObject *pyattr_get_constraintType(PyObjectPlus *self_v, const KX_PYATTRIBUTE_DEF *attrdef);
+	static PyObject *pyattr_get_breakingThreshold(PyObjectPlus *self_v, const KX_PYATTRIBUTE_DEF *attrdef);
+	static int pyattr_set_breakingThreshold(PyObjectPlus *self_v, const KX_PYATTRIBUTE_DEF *attrdef, PyObject *value);
+	static PyObject *pyattr_get_enabled(PyObjectPlus *self_v, const KX_PYATTRIBUTE_DEF *attrdef);
+	static int pyattr_set_enabled(PyObjectPlus *self_v, const KX_PYATTRIBUTE_DEF *attrdef, PyObject *value);
 #endif
 
 private:

source/gameengine/Physics/Bullet/CcdConstraint.cpp

@@ -1,12 +1,15 @@
 #include "CcdConstraint.h"
 
+#include "BLI_utildefines.h"
+
 #include "btBulletDynamicsCommon.h"
 
 CcdConstraint::CcdConstraint(btTypedConstraint *constraint, bool disableCollision)
 	:m_constraint(constraint),
 	m_disableCollision(disableCollision),
-	m_enabled(true)
+	m_active(true)
 {
+	BLI_assert(m_constraint);
 }
 
 CcdConstraint::~CcdConstraint()
@@ -18,21 +21,34 @@ bool CcdConstraint::GetDisableCollision() const
 	return m_disableCollision;
 }
 
+bool CcdConstraint::GetActive() const
+{
+	return m_active;
+}
+
+void CcdConstraint::SetActive(bool active)
+{
+	m_active = active;
+}
+
 bool CcdConstraint::GetEnabled() const
 {
-	return m_enabled;
+	return m_constraint->isEnabled();
 }
 
 void CcdConstraint::SetEnabled(bool enabled)
 {
-	m_enabled = enabled;
+	m_constraint->setEnabled(enabled);
+
+	// Unsleep objects to enable constraint influence.
+	if (enabled) {
+		m_constraint->getRigidBodyA().activate(true);
+		m_constraint->getRigidBodyB().activate(true);
+	}
 }
 
 void CcdConstraint::SetParam(int param, float value0, float value1)
 {
-	if (!m_constraint)
-		return;
-
 	switch (m_constraint->getUserConstraintType())
 	{
 		case PHY_GENERIC_6DOF_CONSTRAINT:
@@ -140,9 +156,6 @@ void CcdConstraint::SetParam(int param, float value0, float value1)
 
 float CcdConstraint::GetParam(int param)
 {
-	if (!m_constraint)
-		return 0.0f;
-
 	switch (m_constraint->getUserConstraintType())
 	{
 		case PHY_GENERIC_6DOF_CONSTRAINT:
@@ -178,6 +191,16 @@ float CcdConstraint::GetParam(int param)
 	return 0.0f;
 }
 
+float CcdConstraint::GetBreakingThreshold() const
+{
+	return m_constraint->getBreakingImpulseThreshold();
+}
+
+void CcdConstraint::SetBreakingThreshold(float threshold)
+{
+	m_constraint->setBreakingImpulseThreshold(threshold);
+}
+
 int CcdConstraint::GetIdentifier() const
 {
 	return m_constraint->getUserConstraintId();

source/gameengine/Physics/Bullet/CcdConstraint.h

@@ -13,19 +13,25 @@ class CcdConstraint : public PHY_IConstraint
 	/// Disable collision between constrained objects?
 	bool m_disableCollision;
 	/// The constraint is added in dynamic world?
-	bool m_enabled;
+	bool m_active;
 
 public:
 	CcdConstraint(btTypedConstraint *constraint, bool disableCollision);
 	virtual ~CcdConstraint();
 
 	bool GetDisableCollision() const;
-	bool GetEnabled() const;
-	void SetEnabled(bool enabled);
+	bool GetActive() const;
+	void SetActive(bool active);
+
+	virtual bool GetEnabled() const;
+	virtual void SetEnabled(bool enabled);
 
 	virtual void SetParam(int param, float value0, float value1);
 	virtual float GetParam(int param);
 
+	virtual float GetBreakingThreshold() const;
+	virtual void SetBreakingThreshold(float threshold);
+
 	virtual int GetIdentifier() const;
 	virtual PHY_ConstraintType GetType() const;
 };

source/gameengine/Physics/Bullet/CcdPhysicsEnvironment.cpp

@@ -499,7 +499,7 @@ void CcdPhysicsEnvironment::AddCcdPhysicsController(CcdPhysicsController *ctrl)
 void CcdPhysicsEnvironment::RemoveConstraint(btTypedConstraint *con, bool free)
 {
 	CcdConstraint *userData = (CcdConstraint *)con->getUserConstraintPtr();
-	if (!userData->GetEnabled()) {
+	if (!userData->GetActive()) {
 		return;
 	}
 
@@ -508,7 +508,7 @@ void CcdPhysicsEnvironment::RemoveConstraint(btTypedConstraint *con, bool free)
 	rbA.activate();
 	rbB.activate();
 
-	userData->SetEnabled(false);
+	userData->SetActive(false);
 	m_dynamicsWorld->removeConstraint(con);
 
 	if (free) {
@@ -539,7 +539,7 @@ void CcdPhysicsEnvironment::RemoveVehicle(WrapperVehicle *vehicle, bool free)
 void CcdPhysicsEnvironment::RestoreConstraint(CcdPhysicsController *ctrl, btTypedConstraint *con)
 {
 	CcdConstraint *userData = (CcdConstraint *)con->getUserConstraintPtr();
-	if (userData->GetEnabled()) {
+	if (userData->GetActive()) {
 		return;
 	}
 
@@ -558,7 +558,7 @@ void CcdPhysicsEnvironment::RestoreConstraint(CcdPhysicsController *ctrl, btType
 
 	// Avoid add constraint if one of the objects are not available.
 	if (IsActiveCcdPhysicsController(other)) {
-		userData->SetEnabled(true);
+		userData->SetActive(true);
 		m_dynamicsWorld->addConstraint(con, userData->GetDisableCollision());
 	}
 }
@@ -3178,6 +3178,10 @@ void CcdPhysicsEnvironment::SetupObjectConstraints(KX_GameObject *obj_src, KX_Ga
 		}
 		dofbit <<= 1;
 	}
+
+	if (dat->flag & CONSTRAINT_USE_BREAKING) {
+		constraint->SetBreakingThreshold(dat->breaking);
+	}
 }
 
 CcdCollData::CcdCollData(const btPersistentManifold *manifoldPoint)

source/gameengine/Physics/Common/PHY_IConstraint.h

@@ -9,9 +9,15 @@ class PHY_IConstraint
 	PHY_IConstraint() = default;
 	virtual ~PHY_IConstraint() = default;
 
+	virtual bool GetEnabled() const = 0;
+	virtual void SetEnabled(bool enabled) = 0;
+
 	virtual void SetParam(int param, float value, float value1) = 0;
 	virtual float GetParam(int param) = 0;
 
+	virtual float GetBreakingThreshold() const = 0;
+	virtual void SetBreakingThreshold(float threshold) = 0;
+
 	virtual int GetIdentifier() const = 0;
 	virtual PHY_ConstraintType GetType() const = 0;
 };