/* -*-c++-*- OpenSceneGraph - Copyright (C) 1998-2006 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>

#ifndef GL_RESCALE_NORMAL
#define GL_RESCALE_NORMAL                 0x803A
#endif

namespace osg {



/** Compute the matrix which transforms objects in local coords to world coords,
  * by accumulating the Transform local to world matrices along the specified node path.
*/
extern OSG_EXPORT Matrix computeLocalToWorld(const NodePath& nodePath, bool ignoreCameras = true);

/** Compute the matrix which transforms objects in world coords to local coords,
  * by accumulating the Transform world to local matrices along the specified node path.
*/
extern OSG_EXPORT Matrix computeWorldToLocal(const NodePath& nodePath, bool ignoreCameras = true);

/** Compute the matrix which transforms objects in local coords to eye coords,
  * by accumulating the Transform local to world matrices along the specified node path 
  * and multipling by the supplied initial camera modelview.
*/
extern OSG_EXPORT Matrix computeLocalToEye(const Matrix& modelview, const NodePath& nodePath, bool ignoreCameras = true);

/** Compute the matrix which transforms objects in eye coords to local coords,
  * by accumulating the Transform world to local matrices along the specified node path
  * and multipling by the inverse of the supplied initialial camera modelview.
*/
extern OSG_EXPORT Matrix computeEyeToLocal(const Matrix& modelview, const NodePath& nodePath, bool ignoreCameras = true);


/** 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 respectively.
  *
  * 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_RESCALE_NORMAL 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 OSG_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; }

        enum ReferenceFrame
        {
            RELATIVE_RF,
            ABSOLUTE_RF,
            ABSOLUTE_RF_INHERIT_VIEWPOINT
        };
        
        /** Set the transform's ReferenceFrame, either to be relative to its
          * parent reference frame, or relative to an absolute coordinate
          * frame. RELATIVE_RF is the default.
          * Note: Setting the ReferenceFrame to be ABSOLUTE_RF 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 recommended to only use
          * absolute Transforms at the top of the scene, for such things as
          * heads up displays.
          * ABSOLUTE_RF_INHERIT_VIEWPOINT is the same as ABSOLUTE_RF except it
          * adds the ability to use the parents view points position in world coordinates
          * as its local viewpoint in the new coordinates frame.  This is useful for
          * Render to texture Cameras that wish to use the main views LOD range computation 
          * (which uses the viewpoint rather than the eye point) rather than use the local
          * eye point defined by the this Transforms' abosolute view matrix.
        */
        void setReferenceFrame(ReferenceFrame rf);
        
        ReferenceFrame getReferenceFrame() const { return _referenceFrame; }

        virtual bool computeLocalToWorldMatrix(Matrix& matrix,NodeVisitor*) const
        {
            if (_referenceFrame==RELATIVE_RF)
            {
                return false;
            }
            else // absolute
            {
                matrix.makeIdentity();
                return true;
            }
        }
        
        virtual bool computeWorldToLocalMatrix(Matrix& matrix,NodeVisitor*) const
        {
            if (_referenceFrame==RELATIVE_RF)
            {
                return false;
            }
            else // absolute
            {
                matrix.makeIdentity();
                return true;
            }
        }

        /** 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 BoundingSphere computeBound() const;

    protected :
    
        virtual ~Transform();
        
        
        ReferenceFrame                      _referenceFrame;

};

}

#endif