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 * ***** BEGIN GPL LICENSE BLOCK *****
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 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
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 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
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 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 *
 * The Original Code is Copyright (C) 2001-2002 by NaN Holding BV.
 * All rights reserved.
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 * ***** END GPL LICENSE BLOCK *****
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/** \file SG_ParentRelation.h
 *  \ingroup bgesg
 * \page SG_ParentRelationPage SG_ParentRelation   
 *
 * \section SG_ParentRelationSection SG_ParentRelation
 * 
 * This is an abstract interface class to the Scene Graph library. 
 * It allows you to specify how child nodes react to parent nodes.
 * Normally a child will use it's parent's transforms to compute
 * it's own global transforms. How this is performed depends on
 * the type of relation. For example if the parent is a vertex 
 * parent to this child then the child should not inherit any 
 * rotation information from the parent. Or if the parent is a
 * 'slow parent' to this child then the child should react 
 * slowly to changes in the parent's position. The exact relation
 * is left for you to implement by filling out this interface 
 * with concrete examples. 
 * 
 * There is exactly one SG_ParentRelation per SG_Node. Subclasses
 * should not be value types and should be allocated on the heap.
 *
 */

#ifndef __SG_PARENTRELATION_H__
#define __SG_PARENTRELATION_H__

class SG_Spatial;

class SG_ParentRelation {

public :
	/**
	 * Update the childs local and global coordinates
	 * based upon the parents global coordinates. 
	 * You must also handle the case when this node has no
	 * parent (parent == NULL). Usually you should just 
	 * copy the local coordinates of the child to the 
	 * world coordinates.
	 */ 
	
	virtual
		bool
	UpdateChildCoordinates(
		SG_Spatial * child,
		const SG_Spatial * parent,
		bool& parentUpdated
	) = 0;

	virtual 
	~SG_ParentRelation(
	) {};

	/** 
	 * You must provide a way of duplicating an
	 * instance of an SG_ParentRelation. This should
	 * return a pointer to a new duplicate allocated
	 * on the heap. Responsibility for deleting the
	 * duplicate resides with the caller of this method.
	 */

	virtual 
		SG_ParentRelation *
	NewCopy(
	) = 0;

	/**
	 * Vertex Parent Relation are special: they don't propagate rotation
	 */
	virtual
		bool
	IsVertexRelation(
	) { 
		return false;
	}
	
	/**
	 * Need this to see if we are able to adjust time-offset from the python api
	 */
	virtual
		bool
	IsSlowRelation(
	) { 
		return false;
	}
protected :

	/** 
	 * Protected constructors 
	 * this class is not meant to be instantiated.
	 */

	SG_ParentRelation(
	) {
	};

	/**
	 * Copy construction should not be implemented
	 */

	SG_ParentRelation(
		const SG_ParentRelation &
	); 
	
	
#ifdef WITH_CXX_GUARDEDALLOC
	MEM_CXX_CLASS_ALLOC_FUNCS("GE:SG_ParentRelation")
#endif
};

#endif

