//C++ header - Open Scene Graph - Copyright (C) 1998-2001 Robert Osfield
//Distributed under the terms of the GNU Library General Public License (LGPL)
//as published by the Free Software Foundation.

#ifndef OSG_TRANSFORM
#define OSG_TRANSFORM 1

#include <osg/Group>
#include <osg/Matrix>

namespace osg {

/** Transform - is group which all children
  * are transformed by the the Transform's osg::Matrix.  Typical uses
  * of the Transform is for positioning objects within a scene or 
  * producing trackball functionality or for animation.
  * Note, if the transformation matrix scales the subgraph then the
  * normals of the underlying geometry will need to be renormalized to
  * be unit vectors once more.  One can done transparently through OpenGL's 
  * use of either GL_NORMALIZE and GL_SCALE_NORMALIZE modes.  Further
  * background reading see the glNormalize documentation in the OpenGL Reference 
  * Guide (the blue book). To enable it in the OSG, you simple need to
  * attach a local osg::StateSet to the osg::Transform, and set the appropriate
  * mode to on via stateset->setMode(GL_NORMALIZE,osg::StateAttribute::ON);.
*/
class SG_EXPORT Transform : public Group
{
    public :

        Transform();

        /** Copy constructor using CopyOp to manage deep vs shallow copy.*/
        Transform(const Transform&,const CopyOp& copyop=CopyOp::SHALLOW_COPY);

        Transform(const Matrix& matix);

        META_Node(Transform);

        /** Range of types that the Transform can be.*/
        enum Type
        {
            DYNAMIC,
            STATIC
        };
        
        /** Set the Transform Type, which can be DYNAMIC - the Matrix
          * value is updated during the main loop, or STATIC - the Matrix
          * is constant throughout the life of the main loop.  STATIC 
          * Transforms can be optimized away is some instances, which
          * can improve performance so unless you plan to modify the
          * Matrix explicitly set the Matrix to STATIC.  The default
          * value is DYNAMIC.*/
        inline void setType(Type type) { _type = type; }

        /** Get the Transform Type.*/
        inline const Type getType() const { return _type; }
        


        enum Mode
        {
            VIEW,
            MODEL
        };

        inline void setMode(Mode mode) { _mode = mode; }
        
        inline const Mode getMode() const { return _mode; }
        

        /** Get the transformation matrix which moves from local coords to world coords.*/
        inline const Matrix& getLocalToWorldMatrix() const { if (_localToWorldDirty) computeLocalToWorld(); return *_localToWorld; }

        /** Get the transformation matrix which moves from world coords to local coords.*/
        inline const Matrix& getWorldToLocalMatrix() const { if (_worldToLocalDirty) computeWorldToLocal(); return *_worldToLocal; }

        

        /** Set the transform's matrix.*/
        void setMatrix(const Matrix& mat);
        
        /** Get the transform's matrix. */
        inline const Matrix& getMatrix() const { if (_mode==MODEL) return *_localToWorld; else return *_worldToLocal; }

        /** preMult transform.*/
        void preMult(const Matrix& mat);
        
        /** postMult transform.*/
        void postMult(const Matrix& mat);
    

    protected :
    
        virtual ~Transform();
        
        /** Override's Group's computeBound. 
          * There is no need to override in subclasses from osg::Transform since this computeBound() uses 
          * the underlying matrix (calling computeMatrix if required.) */
        virtual const bool computeBound() const;
        
        /** If you subclass from osg::Transform you must override computeLocalToWorld() to provide your own mechanism for
          * setting up the 4x4 matrix. An example of a subclass might a PositionAttitudeTransfrom which is its own
          * Vec3 and Quat to calculate the matrix.*/
        virtual void computeLocalToWorld() const;

        /** If you subclass from osg::Transform it must also override computeWorldToLocal() to provide your own mechanism for
          * setting up the 4x4 matrix.*/
        virtual void computeWorldToLocal() const;

        Type                    _type;
        Mode                    _mode;
        
        mutable bool            _localToWorldDirty;
        mutable ref_ptr<Matrix> _localToWorld;
        
        mutable bool            _worldToLocalDirty;
        mutable ref_ptr<Matrix> _worldToLocal;
};

};

#endif