BGE: Fix for applyImpulse function

This is related to task T29419. Credit also goes to Goran Milovanovic
(goran) for proposing an initial fix for this issue.

The issue is the current behavior of applyImpulse doesn't match the behavior
described in the documentation as instead of a impulse point in world coordinates,
it seems to require a coordinate in a local space.

Additionally, applyImpulse function isn't consistent with similar functions (applyForce, applyTorque, etc)
as it doesn't allow  to choose in which space (local or global) the impulse is applied.

Now, we have the following function:

applyImpulse(point, impulse, local=False)
being "point" the point to apply the impulse to (in world or local coordinates). When local is False will
have both point and impulse in World space and when local is True will have point and impulse in local space.

Reviewers: moguri, dfelinto, brita_

Reviewed By: moguri

Differential Revision: https://developer.blender.org/D567

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

@@ -551,7 +551,7 @@ base class --- :class:`SCA_IObject`
 
          This is not implimented at the moment.
 
-   .. method:: applyImpulse(point, impulse)
+   .. method:: applyImpulse(point, impulse, local=False)
 
       Applies an impulse to the game object.
 
@@ -559,8 +559,14 @@ base class --- :class:`SCA_IObject`
       If point != position, applyImpulse will also change the object's angular momentum.
       Otherwise, only linear momentum will change.
 
-      :arg point: the point to apply the impulse to (in world coordinates)
+      :arg point: the point to apply the impulse to (in world or local coordinates)
-      :type point: the point to apply the impulse to (in world coordinates)
+      :type point: point [ix, iy, iz] the point to apply the impulse to (in world or local coordinates)
+      :arg impulse: impulse vector.
+      :type impulse: 3D Vector
+      :arg local:
+         * False: you get the "global" impulse ie: relative to world coordinates with world orientation.
+         * True: you get the "local" impulse ie: relative to local coordinates with object orientation.
+      :type local: boolean
 
    .. method:: suspendDynamics()
 

source/gameengine/Ketsji/KX_GameObject.cpp

@@ -3034,19 +3034,20 @@ PyObject *KX_GameObject::PyApplyImpulse(PyObject *args)
 {
 	PyObject *pyattach;
 	PyObject *pyimpulse;
+	int local = 0;
 	
 	if (!m_pPhysicsController)	{
 		PyErr_SetString(PyExc_RuntimeError, "This object has no physics controller");
 		return NULL;
 	}
 	
-	if (PyArg_ParseTuple(args, "OO:applyImpulse", &pyattach, &pyimpulse))
+	if (PyArg_ParseTuple(args, "OO|i:applyImpulse", &pyattach, &pyimpulse, &local))
 	{
 		MT_Point3  attach;
 		MT_Vector3 impulse;
 		if (PyVecTo(pyattach, attach) && PyVecTo(pyimpulse, impulse))
 		{
-			m_pPhysicsController->ApplyImpulse(attach, impulse);
+			m_pPhysicsController->ApplyImpulse(attach, impulse, (local!=0));
 			Py_RETURN_NONE;
 		}
 

source/gameengine/Physics/Bullet/CcdPhysicsController.cpp

@@ -1309,8 +1309,9 @@ void		CcdPhysicsController::SetLinearVelocity(const MT_Vector3& lin_vel,bool loc
 		}
 	}
 }
-void		CcdPhysicsController::ApplyImpulse(const MT_Point3& attach, const MT_Vector3& impulsein)
+void		CcdPhysicsController::ApplyImpulse(const MT_Point3& attach, const MT_Vector3& impulsein, bool local)
 {
+	btVector3 pos;
 	btVector3 impulse(impulsein.x(), impulsein.y(), impulsein.z());
 
 	if (m_object && impulse.length2() > (SIMD_EPSILON*SIMD_EPSILON))
@@ -1323,7 +1324,19 @@ void		CcdPhysicsController::ApplyImpulse(const MT_Point3& attach, const MT_Vecto
 			return;
 		}
 		
-		btVector3 pos(attach.x(), attach.y(), attach.z());
+		btTransform xform = m_object->getWorldTransform();
+
+		if (local)
+		{
+			pos = btVector3(attach.x(), attach.y(), attach.z());
+			impulse = xform.getBasis() * impulse;
+		}
+		else {
+			/* If the point of impulse application is not equal to the object position
+			 * then an angular momentum is generated in the object*/
+			pos = btVector3(attach.x()-xform.getOrigin().x(), attach.y()-xform.getOrigin().y(), attach.z()-xform.getOrigin().z());
+		}
+
 		btRigidBody* body = GetRigidBody();
 		if (body)
 			body->applyImpulse(impulse,pos);

source/gameengine/Physics/Bullet/CcdPhysicsController.h

@@ -565,7 +565,7 @@ protected:
 		virtual void	SetMass(MT_Scalar newmass);
 		
 		// physics methods
-		virtual void		ApplyImpulse(const MT_Point3& attach, const MT_Vector3& impulsein);
+		virtual void		ApplyImpulse(const MT_Point3& attach, const MT_Vector3& impulsein, bool local);
 		virtual void		ApplyTorque(const MT_Vector3& torque,bool local);
 		virtual void		ApplyForce(const MT_Vector3& force,bool local);
 		virtual void		SetAngularVelocity(const MT_Vector3& ang_vel,bool local);

source/gameengine/Physics/common/PHY_IPhysicsController.h

@@ -82,7 +82,7 @@ class PHY_IPhysicsController : public PHY_IController
 		virtual void		SetMass(MT_Scalar newmass)=0;
 
 		// physics methods
-		virtual void		ApplyImpulse(const MT_Point3& attach, const MT_Vector3& impulse)=0;
+		virtual void		ApplyImpulse(const MT_Point3& attach, const MT_Vector3& impulse,bool local)=0;
 		virtual void		ApplyTorque(const MT_Vector3& torque,bool local)=0;
 		virtual void		ApplyForce(const MT_Vector3& force,bool local)=0;
 		virtual void		SetAngularVelocity(const MT_Vector3& ang_vel,bool local)=0;