Add SetIsSensor to change a body between a sensor and a static body (#82)

Jolt/Physics/Body/Body.h

@@ -63,7 +63,11 @@ public:
 	/// Check if a body could be made kinematic or dynamic (if it was created dynamic or with mAllowDynamicOrKinematic set to true)
 	inline bool				CanBeKinematicOrDynamic() const									{ return mMotionProperties != nullptr; }
 
-	/// Check if this body is a sensor. A sensor will receive collision callbacks, but will not cause any collision responses and can be used as a trigger volume.
+	/// Change the body to a sensor or to a regular static body. A sensor will receive collision callbacks, but will not cause any collision responses and can be used as a trigger volume.
+	/// Note that Sensors need to be of motion type Static (they can be moved around using BodyInterface::SetPosition/SetPositionAndRotation).
+	inline void				SetIsSensor(bool inIsSensor)									{ JPH_ASSERT(!inIsSensor || mMotionProperties == nullptr, "A sensor needs to be Static"); if (inIsSensor) mFlags.fetch_or(uint8(JPH::Body::EFlags::IsSensor), JPH::memory_order_relaxed); else mFlags.fetch_and(uint8(~uint8(JPH::Body::EFlags::IsSensor)), JPH::memory_order_relaxed); }
+
+	/// Check if this body is a sensor.
 	inline bool				IsSensor() const												{ return (mFlags.load(memory_order_relaxed) & uint8(EFlags::IsSensor)) != 0; }
 
 	/// Motion type of this body

Jolt/Physics/Body/BodyManager.cpp

@@ -172,15 +172,13 @@ Body *BodyManager::CreateBody(const BodyCreationSettings &inBodyCreationSettings
 	body->SetRestitution(inBodyCreationSettings.mRestitution);
 	body->mMotionType = inBodyCreationSettings.mMotionType;
 	if (inBodyCreationSettings.mIsSensor)
-		body->mFlags.fetch_or(uint8(Body::EFlags::IsSensor), memory_order_relaxed);
+		body->SetIsSensor(true);
 	SetBodyObjectLayerInternal(*body, inBodyCreationSettings.mObjectLayer);
 	body->mObjectLayer = inBodyCreationSettings.mObjectLayer;
 	body->mCollisionGroup = inBodyCreationSettings.mCollisionGroup;
 	
 	if (inBodyCreationSettings.HasMassProperties())
 	{
-		JPH_ASSERT(!inBodyCreationSettings.mIsSensor, "Sensors should be static and moved through BodyInterface::SetPosition/SetPositionAndRotation");
-
 		MotionProperties *mp = body->mMotionProperties;
 		mp->SetLinearDamping(inBodyCreationSettings.mLinearDamping);
 		mp->SetAngularDamping(inBodyCreationSettings.mAngularDamping);