/* -*-c++-*- OpenSceneGraph - Copyright (C) 1998-2003 Robert Osfield 
 *
 * This library is open source and may be redistributed and/or modified under  
 * the terms of the OpenSceneGraph Public License (OSGPL) version 0.0 or 
 * (at your option) any later version.  The full license is in LICENSE file
 * included with this distribution, and on the openscenegraph.org website.
 * 
 * This library 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 
 * OpenSceneGraph Public License for more details.
*/

#ifndef OSG_TRANSFORM
#define OSG_TRANSFORM 1

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

namespace osg {

/** A Transform is a group node for which all children are transformed by
  * a 4x4 matrix.  It is often used for positioning objects within a scene,
  * producing trackball functionality or for animation.
  *
  * Transform itself does not provide set/get functions, only the interface
  * for defining what the 4x4 transformation is.  Subclasses, such as
  * MatrixTransform and PositionAttitudeTransform support the use of an
  * osg::Matrix or a osg::Vec3/osg::Quat resprectively.
  * The Transform node can be customized via the ComputeTransfromCallback
  * which can be attached to the node.  This might be used to convert from
  * internal representations of the transformation into generic osg::Matrix
  * objects which are used during scene grpah traversal, such as
  * CullTraversal and IntersectionTraversal.
  *
  * 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.  This can be done transparently through OpenGL's 
  * use of either GL_NORMALIZE and GL_SCALE_NORMALIZE modes.  For further
  * background reading see the glNormalize documentation in the OpenGL
  * Reference Guide (the blue book). To enable it in the OSG, you simply
  * 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);

        META_Node(osg, Transform);

        virtual Transform* asTransform() { return this; }
        virtual const Transform* asTransform() const { return this; }

        virtual MatrixTransform* asMatrixTransform() { return 0; }
        virtual const MatrixTransform* asMatrixTransform() const { return 0; }

        virtual PositionAttitudeTransform* asPositionAttitudeTransform() { return 0; }
        virtual const PositionAttitudeTransform* asPositionAttitudeTransform() const { return 0; }

        virtual DOFTransform* asDOFTransform() { return 0; }
        virtual const DOFTransform* asDOFTransform() const { return 0; }

        enum ReferenceFrame
        {
            RELATIVE_TO_PARENTS,
            RELATIVE_TO_ABSOLUTE
        };
        
        /** Set the transform's ReferenceFrame, either to be relative to its
          * parent reference frame, or relative to an absolute coordinate
          * frame. RELATIVE_TO_PARENTS is the default.
          * Note: setting the ReferenceFrame to be RELATIVE_TO_ABSOLUTE will
          * also set the CullingActive flag on the transform, and hence all
          * of its parents, to false, thereby disabling culling of it and
          * all its parents.  This is neccessary to prevent inappropriate
          * culling, but may impact cull times if the absolute transform is
          * deep in the scene graph.  It is therefore recommend to only use
          * absolute Transforms at the top of the scene, for such things as
          * heads up displays. */
        void setReferenceFrame(ReferenceFrame rf);
        
        ReferenceFrame getReferenceFrame() const { return _referenceFrame; }

        
        /** Callback attached to an Transform to specify how to compute the
          * modelview transformation for the transform below the Transform
          * node. */
        struct ComputeTransformCallback : public virtual osg::Referenced
        {
            /** Get the transformation matrix which moves from local coords
              * to world coords.*/
            virtual bool computeLocalToWorldMatrix(Matrix& matrix,const Transform* transform, NodeVisitor* nv) const = 0;

            /** Get the transformation matrix which moves from world coords
              * to local coords.*/
            virtual bool computeWorldToLocalMatrix(Matrix& matrix,const Transform* transform, NodeVisitor* nv) const = 0;
        };

        /** Set the ComputerTransfromCallback which allows users to attach
          * custom computation of the local transformation as seen by cull
          * traversers and the like. */
        void setComputeTransformCallback(ComputeTransformCallback* ctc) { _computeTransformCallback=ctc; dirtyBound(); }
        
        /** Get the non const ComputerTransfromCallback.*/
        ComputeTransformCallback* getComputeTransformCallback() { return _computeTransformCallback.get(); }
        
        /** Get the const ComputerTransfromCallback.*/
        const ComputeTransformCallback* getComputeTransformCallback() const { return _computeTransformCallback.get(); }


        /** Get the transformation matrix which moves from local coords to
          * world coords.
          * Returns true if the Matrix passed in has been updated. */
        inline bool getLocalToWorldMatrix(Matrix& matrix,NodeVisitor* nv) const
        {
            if (_computeTransformCallback.valid())
                return _computeTransformCallback->computeLocalToWorldMatrix(matrix,this,nv);
            else
                return computeLocalToWorldMatrix(matrix,nv);
        }
        
        /** Get the transformation matrix which moves from world coords to
          * local coords.
          * Return true if the Matrix passed in has been updated. */
        inline bool getWorldToLocalMatrix(Matrix& matrix,NodeVisitor* nv) const
        {
            if (_computeTransformCallback.valid())
                return _computeTransformCallback->computeWorldToLocalMatrix(matrix,this,nv);
            else
                return computeWorldToLocalMatrix(matrix,nv);
        }
        
        virtual bool computeLocalToWorldMatrix(Matrix& matrix,NodeVisitor*) const
        {
            if (_referenceFrame==RELATIVE_TO_PARENTS)
            {
                return false;
            }
            else // absolute
            {
                matrix.makeIdentity();
                return true;
            }
        }
        
        virtual bool computeWorldToLocalMatrix(Matrix& matrix,NodeVisitor*) const
        {
            if (_referenceFrame==RELATIVE_TO_PARENTS)
            {
                return false;
            }
            else // absolute
            {
                matrix.makeIdentity();
                return true;
            }
        }

    protected :
    
        virtual ~Transform();
        
        /** Overrides 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 bool computeBound() const;
        
        
        ref_ptr<ComputeTransformCallback>   _computeTransformCallback;

        ReferenceFrame                      _referenceFrame;

};

}

#endif