/*
-----------------------------------------------------------------------------
This source file is part of OGRE
    (Object-oriented Graphics Rendering Engine)
For the latest info, see http://www.ogre3d.org/

Copyright (c) 2000-2006 Torus Knot Software Ltd
Also see acknowledgements in Readme.html

This program is free software; you can redistribute it and/or modify it under
the terms of the GNU Lesser General Public License as published by the Free Software
Foundation; either version 2 of the License, or (at your option) any later
version.

This program is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public License along with
this program; if not, write to the Free Software Foundation, Inc., 59 Temple
Place - Suite 330, Boston, MA 02111-1307, USA, or go to
http://www.gnu.org/copyleft/lesser.txt.

You may alternatively use this source under the terms of a specific version of
the OGRE Unrestricted License provided you have obtained such a license from
Torus Knot Software Ltd.
-----------------------------------------------------------------------------
*/
#ifndef _Node_H__
#define _Node_H__

#include "OgrePrerequisites.h"

#include "OgreMatrix3.h"
#include "OgreMatrix4.h"
#include "OgreQuaternion.h"
#include "OgreString.h"
#include "OgreRenderable.h"
#include "OgreIteratorWrappers.h"

namespace Ogre {


    /** Class representing a general-purpose node an articulated scene graph.
        @remarks
            A node in the scene graph is a node in a structured tree. A node contains
            information about the transformation which will apply to
            it and all of it's children. Child nodes can have transforms of their own, which
            are combined with their parent's transformations.
        @par
            This is an abstract class - concrete classes are based on this for specific purposes,
            e.g. SceneNode, Bone
    */
    class _OgreExport Node : public Renderable
    {
    public:
        /** Enumeration denoting the spaces which a transform can be relative to.
        */
        enum TransformSpace
        {
            /// Transform is relative to the local space
            TS_LOCAL,
            /// Transform is relative to the space of the parent node
            TS_PARENT,
            /// Transform is relative to world space
            TS_WORLD
        };
        typedef HashMap<String, Node*> ChildNodeMap;
        typedef MapIterator<ChildNodeMap> ChildNodeIterator;
		typedef ConstMapIterator<ChildNodeMap> ConstChildNodeIterator;

		/** Listener which gets called back on Node events.
		*/
		class _OgreExport Listener
		{
		public:
			Listener() {}
			virtual ~Listener() {}
			/** Called when a node gets updated.
			@remarks
				Note that this happens when the node's derived update happens,
				not every time a method altering it's state occurs. There may 
				be several state-changing calls but only one of these calls, 
				when the node graph is fully updated.
			*/
			virtual void nodeUpdated(const Node*) {}
			/** Node is being destroyed */
			virtual void nodeDestroyed(const Node*) {};
			/** Node has been attached to a parent */
			virtual void nodeAttached(const Node*) {};
			/** Node has been detached from a parent */
			virtual void nodeDetached(const Node*) {};
		};

    protected:
        /// Pointer to parent node
        Node* mParent;
        /// Collection of pointers to direct children; hashmap for efficiency
        ChildNodeMap mChildren;

		typedef std::set<Node*> ChildUpdateSet;
        /// List of children which need updating, used if self is not out of date but children are
        mutable ChildUpdateSet mChildrenToUpdate;
        /// Flag to indicate own transform from parent is out of date
        mutable bool mNeedParentUpdate;
		/// Flag indicating that all children need to be updated
		mutable bool mNeedChildUpdate;
		/// Flag indicating that parent has been notified about update request
	    mutable bool mParentNotified ;
        /// Flag indicating that the node has been queued for update
        mutable bool mQueuedForUpdate;

        /// Friendly name of this node, can be automatically generated if you don't care
        String mName;

        /// Incremented count for next name extension
        static unsigned long msNextGeneratedNameExt;

        /// Stores the orientation of the node relative to it's parent.
        Quaternion mOrientation;

        /// Stores the position/translation of the node relative to its parent.
        Vector3 mPosition;

        /// Stores the scaling factor applied to this node
        Vector3 mScale;

        /// Stores whether this node inherits orientation from it's parent
        bool mInheritOrientation;

        /// Stores whether this node inherits scale from it's parent
        bool mInheritScale;

		/// Material pointer should this node be rendered
		mutable MaterialPtr mpMaterial;

        /// Only available internally - notification of parent.
        virtual void setParent(Node* parent);

        /** Cached combined orientation.
            @par
                This member is the orientation derived by combining the
                local transformations and those of it's parents.
                This is updated when _updateFromParent is called by the
                SceneManager or the nodes parent.
        */
        mutable Quaternion mDerivedOrientation;

        /** Cached combined position.
            @par
                This member is the position derived by combining the
                local transformations and those of it's parents.
                This is updated when _updateFromParent is called by the
                SceneManager or the nodes parent.
        */
        mutable Vector3 mDerivedPosition;

        /** Cached combined scale.
            @par
                This member is the position derived by combining the
                local transformations and those of it's parents.
                This is updated when _updateFromParent is called by the
                SceneManager or the nodes parent.
        */
        mutable Vector3 mDerivedScale;

        /** Triggers the node to update it's combined transforms.
            @par
                This method is called internally by Ogre to ask the node
                to update it's complete transformation based on it's parents
                derived transform.
        */
        virtual void _updateFromParent(void) const;

		/** Class-specific implementation of _updateFromParent.
		@remarks
			Splitting the implementation of the update away from the update call
			itself allows the detail to be overridden without disrupting the 
			general sequence of updateFromParent (e.g. raising events)
		*/
		virtual void updateFromParentImpl(void) const;


        /** Internal method for creating a new child node - must be overridden per subclass. */
        virtual Node* createChildImpl(void) = 0;

        /** Internal method for creating a new child node - must be overridden per subclass. */
        virtual Node* createChildImpl(const String& name) = 0;

        /// The position to use as a base for keyframe animation
        Vector3 mInitialPosition;
        /// The orientation to use as a base for keyframe animation
        Quaternion mInitialOrientation;
        /// The scale to use as a base for keyframe animation
        Vector3 mInitialScale;

        /// Cached derived transform as a 4x4 matrix
        mutable Matrix4 mCachedTransform;
        mutable bool mCachedTransformOutOfDate;

		/** Node listener - only one allowed (no list) for size & performance reasons. */
		Listener* mListener;

		typedef std::vector<Node*> QueuedUpdates;
		static QueuedUpdates msQueuedUpdates;


    public:
        /** Constructor, should only be called by parent, not directly.
        @remarks
            Generates a name.
        */
        Node();
        /** Constructor, should only be called by parent, not directly.
        @remarks
            Assigned a name.
        */
        Node(const String& name);

        virtual ~Node();  

        /** Returns the name of the node. */
        const String& getName(void) const;

        /** Gets this node's parent (NULL if this is the root).
        */
        virtual Node* getParent(void) const;

        /** Returns a quaternion representing the nodes orientation.
        */
        virtual const Quaternion & getOrientation() const;

        /** Sets the orientation of this node via a quaternion.
        @remarks
            Orientatings, unlike other transforms, are not always inherited by child nodes.
            Whether or not orientatings affect the orientation of the child nodes depends on
            the setInheritOrientation option of the child. In some cases you want a orientating
            of a parent node to apply to a child node (e.g. where the child node is a part of
            the same object, so you want it to be the same relative orientation based on the
            parent's orientation), but not in other cases (e.g. where the child node is just
            for positioning another object, you want it to maintain it's own orientation).
            The default is to inherit as with other transforms.
        @par
            Note that rotations are oriented around the node's origin.
        */
        virtual void setOrientation( const Quaternion& q );

        /** Sets the orientation of this node via quaternion parameters.
        @remarks
            Orientatings, unlike other transforms, are not always inherited by child nodes.
            Whether or not orientatings affect the orientation of the child nodes depends on
            the setInheritOrientation option of the child. In some cases you want a orientating
            of a parent node to apply to a child node (e.g. where the child node is a part of
            the same object, so you want it to be the same relative orientation based on the
            parent's orientation), but not in other cases (e.g. where the child node is just
            for positioning another object, you want it to maintain it's own orientation).
            The default is to inherit as with other transforms.
        @par
            Note that rotations are oriented around the node's origin.
        */
        virtual void setOrientation( Real w, Real x, Real y, Real z);

        /** Resets the nodes orientation (local axes as world axes, no rotation).
        @remarks
            Orientatings, unlike other transforms, are not always inherited by child nodes.
            Whether or not orientatings affect the orientation of the child nodes depends on
            the setInheritOrientation option of the child. In some cases you want a orientating
            of a parent node to apply to a child node (e.g. where the child node is a part of
            the same object, so you want it to be the same relative orientation based on the
            parent's orientation), but not in other cases (e.g. where the child node is just
            for positioning another object, you want it to maintain it's own orientation).
            The default is to inherit as with other transforms.
        @par
            Note that rotations are oriented around the node's origin.
        */
        virtual void resetOrientation(void);

        /** Sets the position of the node relative to it's parent.
        */
        virtual void setPosition(const Vector3& pos);

        /** Sets the position of the node relative to it's parent.
        */
        virtual void setPosition(Real x, Real y, Real z);

        /** Gets the position of the node relative to it's parent.
        */
        virtual const Vector3 & getPosition(void) const;

        /** Sets the scaling factor applied to this node.
        @remarks
            Scaling factors, unlike other transforms, are not always inherited by child nodes.
            Whether or not scalings affect the size of the child nodes depends on the setInheritScale
            option of the child. In some cases you want a scaling factor of a parent node to apply to
            a child node (e.g. where the child node is a part of the same object, so you want it to be
            the same relative size based on the parent's size), but not in other cases (e.g. where the
            child node is just for positioning another object, you want it to maintain it's own size).
            The default is to inherit as with other transforms.
        @par
            Note that like rotations, scalings are oriented around the node's origin.
        */
        virtual void setScale(const Vector3& scale);

        /** Sets the scaling factor applied to this node.
        @remarks
            Scaling factors, unlike other transforms, are not always inherited by child nodes.
            Whether or not scalings affect the size of the child nodes depends on the setInheritScale
            option of the child. In some cases you want a scaling factor of a parent node to apply to
            a child node (e.g. where the child node is a part of the same object, so you want it to be
            the same relative size based on the parent's size), but not in other cases (e.g. where the
            child node is just for positioning another object, you want it to maintain it's own size).
            The default is to inherit as with other transforms.
        @par
            Note that like rotations, scalings are oriented around the node's origin.
        */
        virtual void setScale(Real x, Real y, Real z);

        /** Gets the scaling factor of this node.
        */
        virtual const Vector3 & getScale(void) const;

        /** Tells the node whether it should inherit orientation from it's parent node.
        @remarks
            Orientatings, unlike other transforms, are not always inherited by child nodes.
            Whether or not orientatings affect the orientation of the child nodes depends on
            the setInheritOrientation option of the child. In some cases you want a orientating
            of a parent node to apply to a child node (e.g. where the child node is a part of
            the same object, so you want it to be the same relative orientation based on the
            parent's orientation), but not in other cases (e.g. where the child node is just
            for positioning another object, you want it to maintain it's own orientation).
            The default is to inherit as with other transforms.
        @param inherit If true, this node's orientation will be affected by its parent's orientation.
            If false, it will not be affected.
        */
        virtual void setInheritOrientation(bool inherit);

        /** Returns true if this node is affected by orientation applied to the parent node. 
        @remarks
            Orientatings, unlike other transforms, are not always inherited by child nodes.
            Whether or not orientatings affect the orientation of the child nodes depends on
            the setInheritOrientation option of the child. In some cases you want a orientating
            of a parent node to apply to a child node (e.g. where the child node is a part of
            the same object, so you want it to be the same relative orientation based on the
            parent's orientation), but not in other cases (e.g. where the child node is just
            for positioning another object, you want it to maintain it's own orientation).
            The default is to inherit as with other transforms.
        @remarks
            See setInheritOrientation for more info.
        */
        virtual bool getInheritOrientation(void) const;

        /** Tells the node whether it should inherit scaling factors from it's parent node.
        @remarks
            Scaling factors, unlike other transforms, are not always inherited by child nodes.
            Whether or not scalings affect the size of the child nodes depends on the setInheritScale
            option of the child. In some cases you want a scaling factor of a parent node to apply to
            a child node (e.g. where the child node is a part of the same object, so you want it to be
            the same relative size based on the parent's size), but not in other cases (e.g. where the
            child node is just for positioning another object, you want it to maintain it's own size).
            The default is to inherit as with other transforms.
        @param inherit If true, this node's scale will be affected by its parent's scale. If false,
            it will not be affected.
        */
        virtual void setInheritScale(bool inherit);

        /** Returns true if this node is affected by scaling factors applied to the parent node. 
        @remarks
            See setInheritScale for more info.
        */
        virtual bool getInheritScale(void) const;

        /** Scales the node, combining it's current scale with the passed in scaling factor. 
        @remarks
            This method applies an extra scaling factor to the node's existing scale, (unlike setScale
            which overwrites it) combining it's current scale with the new one. E.g. calling this 
            method twice with Vector3(2,2,2) would have the same effect as setScale(Vector3(4,4,4)) if
            the existing scale was 1.
        @par
            Note that like rotations, scalings are oriented around the node's origin.
        */
        virtual void scale(const Vector3& scale);

        /** Scales the node, combining it's current scale with the passed in scaling factor. 
        @remarks
            This method applies an extra scaling factor to the node's existing scale, (unlike setScale
            which overwrites it) combining it's current scale with the new one. E.g. calling this 
            method twice with Vector3(2,2,2) would have the same effect as setScale(Vector3(4,4,4)) if
            the existing scale was 1.
        @par
            Note that like rotations, scalings are oriented around the node's origin.
        */
        virtual void scale(Real x, Real y, Real z);

        /** Moves the node along the cartesian axes.
            @par
                This method moves the node by the supplied vector along the
                world cartesian axes, i.e. along world x,y,z
            @param 
                d Vector with x,y,z values representing the translation.
            @param
                relativeTo The space which this transform is relative to.
        */
        virtual void translate(const Vector3& d, TransformSpace relativeTo = TS_PARENT);
        /** Moves the node along the cartesian axes.
            @par
                This method moves the node by the supplied vector along the
                world cartesian axes, i.e. along world x,y,z
            @param 
                x
            @param
                y
            @param
                z Real x, y and z values representing the translation.
            @param
            relativeTo The space which this transform is relative to.
        */
        virtual void translate(Real x, Real y, Real z, TransformSpace relativeTo = TS_PARENT);
        /** Moves the node along arbitrary axes.
            @remarks
                This method translates the node by a vector which is relative to
                a custom set of axes.
            @param 
                axes A 3x3 Matrix containg 3 column vectors each representing the
                axes X, Y and Z respectively. In this format the standard cartesian
                axes would be expressed as:
                <pre>
                1 0 0
                0 1 0
                0 0 1
                </pre>
                i.e. the identity matrix.
            @param 
                move Vector relative to the axes above.
            @param
            relativeTo The space which this transform is relative to.
        */
        virtual void translate(const Matrix3& axes, const Vector3& move, TransformSpace relativeTo = TS_PARENT);
        /** Moves the node along arbitrary axes.
            @remarks
            This method translates the node by a vector which is relative to
            a custom set of axes.
            @param 
                axes A 3x3 Matrix containg 3 column vectors each representing the
                axes X, Y and Z respectively. In this format the standard cartesian
                axes would be expressed as
                <pre>
                1 0 0
                0 1 0
                0 0 1
                </pre>
                i.e. the identity matrix.
            @param 
                x,y,z Translation components relative to the axes above.
            @param
                relativeTo The space which this transform is relative to.
        */
        virtual void translate(const Matrix3& axes, Real x, Real y, Real z, TransformSpace relativeTo = TS_PARENT);

        /** Rotate the node around the Z-axis.
        */
        virtual void roll(const Radian& angle, TransformSpace relativeTo = TS_LOCAL);
#ifndef OGRE_FORCE_ANGLE_TYPES
        inline void roll(Real degrees, TransformSpace relativeTo = TS_LOCAL) {
			roll ( Angle(degrees), relativeTo );
		}
#endif//OGRE_FORCE_ANGLE_TYPES

        /** Rotate the node around the X-axis.
        */
        virtual void pitch(const Radian& angle, TransformSpace relativeTo = TS_LOCAL);
#ifndef OGRE_FORCE_ANGLE_TYPES
        inline void pitch(Real degrees, TransformSpace relativeTo = TS_LOCAL) {
			pitch ( Angle(degrees), relativeTo );
		}
#endif//OGRE_FORCE_ANGLE_TYPES

        /** Rotate the node around the Y-axis.
        */
        virtual void yaw(const Radian& angle, TransformSpace relativeTo = TS_LOCAL);
#ifndef OGRE_FORCE_ANGLE_TYPES
        inline void yaw(Real degrees, TransformSpace relativeTo = TS_LOCAL) {
			yaw ( Angle(degrees), relativeTo );
		}
#endif//OGRE_FORCE_ANGLE_TYPES

        /** Rotate the node around an arbitrary axis.
        */
        virtual void rotate(const Vector3& axis, const Radian& angle, TransformSpace relativeTo = TS_LOCAL);
#ifndef OGRE_FORCE_ANGLE_TYPES
        inline void rotate(const Vector3& axis, Real degrees, TransformSpace relativeTo = TS_LOCAL) {
			rotate ( axis, Angle(degrees), relativeTo );
		}
#endif//OGRE_FORCE_ANGLE_TYPES

        /** Rotate the node around an aritrary axis using a Quarternion.
        */
        virtual void rotate(const Quaternion& q, TransformSpace relativeTo = TS_LOCAL);

        /** Gets a matrix whose columns are the local axes based on
            the nodes orientation relative to it's parent. */
        virtual Matrix3 getLocalAxes(void) const;

        /** Creates an unnamed new Node as a child of this node.
        @param
            translate Initial translation offset of child relative to parent
        @param
            rotate Initial rotation relative to parent
        */
        virtual Node* createChild(
            const Vector3& translate = Vector3::ZERO, 
            const Quaternion& rotate = Quaternion::IDENTITY );

        /** Creates a new named Node as a child of this node.
        @remarks
            This creates a child node with a given name, which allows you to look the node up from 
            the parent which holds this collection of nodes.
            @param
                translate Initial translation offset of child relative to parent
            @param
                rotate Initial rotation relative to parent
        */
        virtual Node* createChild(const String& name, const Vector3& translate = Vector3::ZERO, const Quaternion& rotate = Quaternion::IDENTITY);

        /** Adds a (precreated) child scene node to this node. If it is attached to another node,
            it must be detached first.
        @param child The Node which is to become a child node of this one
        */
        virtual void addChild(Node* child);

        /** Reports the number of child nodes under this one.
        */
        virtual unsigned short numChildren(void) const;

        /** Gets a pointer to a child node.
        @remarks
            There is an alternate getChild method which returns a named child.
        */
        virtual Node* getChild(unsigned short index) const;    

        /** Gets a pointer to a named child node.
        */
        virtual Node* getChild(const String& name) const;

        /** Retrieves an iterator for efficiently looping through all children of this node.
        @remarks
            Using this is faster than repeatedly calling getChild if you want to go through
            all (or most of) the children of this node.
            Note that the returned iterator is only valid whilst no children are added or
            removed from this node. Thus you should not store this returned iterator for
            later use, nor should you add / remove children whilst iterating through it;
            store up changes for later. Note that calling methods on returned items in 
            the iterator IS allowed and does not invalidate the iterator.
        */
        virtual ChildNodeIterator getChildIterator(void);

        /** Retrieves an iterator for efficiently looping through all children of this node.
        @remarks
            Using this is faster than repeatedly calling getChild if you want to go through
            all (or most of) the children of this node.
            Note that the returned iterator is only valid whilst no children are added or
            removed from this node. Thus you should not store this returned iterator for
            later use, nor should you add / remove children whilst iterating through it;
            store up changes for later. Note that calling methods on returned items in 
            the iterator IS allowed and does not invalidate the iterator.
        */
		virtual ConstChildNodeIterator getChildIterator(void) const;

        /** Drops the specified child from this node. 
        @remarks
            Does not delete the node, just detaches it from
            this parent, potentially to be reattached elsewhere. 
            There is also an alternate version which drops a named
            child from this node.
        */
        virtual Node* removeChild(unsigned short index);
        /** Drops the specified child from this node. 
        @remarks
        Does not delete the node, just detaches it from
        this parent, potentially to be reattached elsewhere. 
        There is also an alternate version which drops a named
        child from this node.
        */
        virtual Node* removeChild(Node* child);

        /** Drops the named child from this node. 
        @remarks
            Does not delete the node, just detaches it from
            this parent, potentially to be reattached elsewhere.
        */
        virtual Node* removeChild(const String& name);
        /** Removes all child Nodes attached to this node. Does not delete the nodes, just detaches them from
            this parent, potentially to be reattached elsewhere.
        */
        virtual void removeAllChildren(void);

        /** Gets the orientation of the node as derived from all parents.
        */
        virtual const Quaternion & _getDerivedOrientation(void) const;

        /** Gets the position of the node as derived from all parents.
        */
        virtual const Vector3 & _getDerivedPosition(void) const;

        /** Gets the scaling factor of the node as derived from all parents.
        */
        virtual const Vector3 & _getDerivedScale(void) const;

        /** Gets the full transformation matrix for this node.
            @remarks
                This method returns the full transformation matrix
                for this node, including the effect of any parent node
                transformations, provided they have been updated using the Node::_update method.
                This should only be called by a SceneManager which knows the
                derived transforms have been updated before calling this method.
                Applications using Ogre should just use the relative transforms.
        */
        virtual const Matrix4& _getFullTransform(void) const;

        /** Internal method to update the Node.
            @note
                Updates this node and any relevant children to incorporate transforms etc.
                Don't call this yourself unless you are writing a SceneManager implementation.
            @param
                updateChildren If true, the update cascades down to all children. Specify false if you wish to
                update children separately, e.g. because of a more selective SceneManager implementation.
            @param
                parentHasChanged This flag indicates that the parent xform has changed,
                    so the child should retrieve the parent's xform and combine it with its own
                    even if it hasn't changed itself.
        */
        virtual void _update(bool updateChildren, bool parentHasChanged);

        /** Sets a listener for this Node.
		@remarks
			Note for size and performance reasons only one listener per node is
			allowed.
		*/
		virtual void setListener(Listener* listener) { mListener = listener; }
		
		/** Gets the current listener for this Node.
		*/
		virtual Listener* getListener(void) const { return mListener; }
		
		/** Overridden from Renderable.
        @remarks
            This is only used if the SceneManager chooses to render the node. This option can be set
            for SceneNodes at SceneManager::setDisplaySceneNodes, and for entities based on skeletal 
            models using Entity::setDisplayBones()
        */
        const MaterialPtr& getMaterial(void) const;
        /** Overridden from Renderable.
        @remarks
            This is only used if the SceneManager chooses to render the node. This option can be set
            for SceneNodes at SceneManager::setDisplaySceneNodes, and for entities based on skeletal 
            models using Entity::setDisplaySkeleton()
        */
        void getRenderOperation(RenderOperation& op);
        /** Overridden from Renderable.
        @remarks
            This is only used if the SceneManager chooses to render the node. This option can be set
            for SceneNodes at SceneManager::setDisplaySceneNodes, and for entities based on skeletal 
            models using Entity::setDisplaySkeleton()
        */
        void getWorldTransforms(Matrix4* xform) const;
        /** @copydoc Renderable::getWorldOrientation */
        const Quaternion& getWorldOrientation(void) const;
        /** @copydoc Renderable::getWorldPosition */
        const Vector3& getWorldPosition(void) const;

        /** Sets the current transform of this node to be the 'initial state' ie that
            position / orientation / scale to be used as a basis for delta values used
            in keyframe animation.
        @remarks
            You never need to call this method unless you plan to animate this node. If you do
            plan to animate it, call this method once you've loaded the node with it's base state,
            ie the state on which all keyframes are based.
        @par
            If you never call this method, the initial state is the identity transform, ie do nothing.
        */
        virtual void setInitialState(void);

        /** Resets the position / orientation / scale of this node to it's initial state, see setInitialState for more info. */
        virtual void resetToInitialState(void);

        /** Gets the initial position of this node, see setInitialState for more info. 
        @remarks
            Also resets the cumulative animation weight used for blending.
        */
        virtual const Vector3& getInitialPosition(void) const;

        /** Gets the initial orientation of this node, see setInitialState for more info. */
        virtual const Quaternion& getInitialOrientation(void) const;

        /** Gets the initial position of this node, see setInitialState for more info. */
        virtual const Vector3& getInitialScale(void) const;

        /** Overridden, see Renderable */
        Real getSquaredViewDepth(const Camera* cam) const;

        /** To be called in the event of transform changes to this node that require it's recalculation.
        @remarks
            This not only tags the node state as being 'dirty', it also requests it's parent to 
            know about it's dirtiness so it will get an update next time.
		@param forceParentUpdate Even if the node thinks it has already told it's
			parent, tell it anyway
        */
        virtual void needUpdate(bool forceParentUpdate = false);
        /** Called by children to notify their parent that they need an update. 
		@param forceParentUpdate Even if the node thinks it has already told it's
			parent, tell it anyway
		*/
        virtual void requestUpdate(Node* child, bool forceParentUpdate = false);
        /** Called by children to notify their parent that they no longer need an update. */
        virtual void cancelUpdate(Node* child);

		/** Queue a 'needUpdate' call to a node safely.
		@ramarks
			You can't call needUpdate() during the scene graph update, e.g. in
			response to a Node::Listener hook, because the graph is already being 
			updated, and update flag changes cannot be made reliably in that context. 
			Call this method if you need to queue a needUpdate call in this case.
		*/
		static void queueNeedUpdate(Node* n);
		/** Process queued 'needUpdate' calls. */
		static void processQueuedUpdates(void);

        /** @copydoc Renderable::getLights */
        const LightList& getLights(void) const;



    };

} //namespace

#endif
