Allow nodes ignoring parent transformations with ESNUA_RELATIVE

New AbsPosUpdateBehavior which makes updateAbsolutePosition calls behave as if a node had no parent.
Allows for micro optimizations in cases where we have non-moving root node (all scenenodes are always added to the SceneManager which is generally not moved but it's transformation is still multiplied each frame for each node)
As a side-effect this also allows abusing the SceneManager to group objects without affecting transformations.
No real extra cost since I added ESNUA_TRANSFORM_POSITION already.
Thought turns out those matrix transformations are so fast that I also didn't noticed any difference in tests with > 20.000 nodes.


git-svn-id: svn://svn.code.sf.net/p/irrlicht/code/trunk@6481 dfc29bdd-3216-0410-991c-e03cc46cb475

include/ESceneNodeUpdateAbs.h

@@ -17,7 +17,11 @@ namespace scene
 		//! Only transform the position of the node transformation matrix 
 		//! by the parent transformation matrix.
 		//! Parent will not affect the rotation/scale of the node transformation.
-		ESNUA_TRANSFORM_POSITION
+		ESNUA_TRANSFORM_POSITION,
+
+		//! Use the relative matrix as absolute transformation matrix
+		//! Parent node transformation is ignored just like when the parent is set to 0
+		ESNUA_RELATIVE
 	};
 
 	//! Names for culling type
@@ -25,6 +29,7 @@ namespace scene
 	{
 		"matrix",
 		"pos",
+		"relative",
 		0
 	};