add option to disable btMultiBody self-collision (for the entire hierarchy) or to disable parent-child collision for jointed links.

src/BulletDynamics/Featherstone/btMultiBodyLinkCollider.h

@@ -33,6 +33,7 @@ public:
 		:m_multiBody(multiBody),
 		m_link(link)
 	{
+		m_checkCollideWith =  true;
 		//we need to remove the 'CF_STATIC_OBJECT' flag, otherwise links/base doesn't merge islands
 		//this means that some constraints might point to bodies that are not in the islands, causing crashes
 		//if (link>=0 || (multiBody && !multiBody->hasFixedBase()))
@@ -59,6 +60,32 @@ public:
 		return 0;
 	}
 
+	virtual bool checkCollideWithOverride(const  btCollisionObject* co) const
+	{
+		const btMultiBodyLinkCollider* other = btMultiBodyLinkCollider::upcast(co);
+		if (!other)
+			return true;
+		if (other->m_multiBody != this->m_multiBody)
+			return true;
+		if (!m_multiBody->hasSelfCollision())
+			return false;
+
+		//check if 'link' has collision disabled
+		if (m_link>=0)
+		{
+			const btMultibodyLink& link = m_multiBody->getLink(this->m_link);
+			if ((link.m_flags&BT_MULTIBODYLINKFLAGS_DISABLE_PARENT_COLLISION) && link.parent == other->m_link)
+				return false;
+		}
+		
+		if (other->m_link>=0)
+		{
+			const btMultibodyLink& otherLink = other->m_multiBody->getLink(other->m_link);
+			if ((otherLink.m_flags& BT_MULTIBODYLINKFLAGS_DISABLE_PARENT_COLLISION) && otherLink.parent == this->m_link)
+				return false;
+		}
+		return true;
+	}
 };
 
 #endif //BT_FEATHERSTONE_LINK_COLLIDER_H