/* -*-c++-*- OpenSceneGraph - Copyright (C) 1998-2005 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 OSGUTIL_TANGENTSPACEGENERATOR_
#define OSGUTIL_TANGENTSPACEGENERATOR_

#include <osgUtil/Export>

#include <osg/ref_ptr>
#include <osg/Referenced>
#include <osg/Array>
#include <osg/Geometry>

namespace osgUtil
{

/**
 The TangentSpaceGenerator class generates three arrays containing tangent-space basis vectors.
 It takes a texture-mapped Geometry object as input, traverses its primitive sets and computes
 Tangent, Normal and Binormal vectors for each vertex, storing them into arrays.
 The resulting arrays can be used as vertex program varying (per-vertex) parameters,
 enabling advanced effects like bump-mapping.
 To use this class, simply call the generate() method specifying the Geometry object
 you want to process and the texture unit that contains UV mapping for the normal map;
 then you can retrieve the TBN arrays by calling getTangentArray(), getNormalArray()
 and getBinormalArray() methods.
 */
class OSGUTIL_EXPORT TangentSpaceGenerator: public osg::Referenced {
public:
    TangentSpaceGenerator();
    TangentSpaceGenerator(const TangentSpaceGenerator &copy, const osg::CopyOp &copyop = osg::CopyOp::SHALLOW_COPY);

    void generate(osg::Geometry *geo, int normal_map_tex_unit = 0);

    inline osg::Vec4Array *getTangentArray()               { return T_.get(); }
    inline const osg::Vec4Array *getTangentArray() const   { return T_.get(); }
    inline void setTangentArray(osg::Vec4Array *array)     { T_ = array; }

    inline osg::Vec4Array *getNormalArray()                { return N_.get(); }
    inline const osg::Vec4Array *getNormalArray() const    { return N_.get(); }
    inline void setNormalArray(osg::Vec4Array *array)      { N_ = array; }

    inline osg::Vec4Array *getBinormalArray()              { return B_.get(); }
    inline const osg::Vec4Array *getBinormalArray() const  { return B_.get(); }
    inline void setBinormalArray(osg::Vec4Array *array)    { B_ = array; }

    inline osg::IndexArray *getIndices() { return indices_.get(); }
protected:
    virtual ~TangentSpaceGenerator() {}
    TangentSpaceGenerator &operator=(const TangentSpaceGenerator &) { return *this; }

    void compute_basis_vectors(osg::PrimitiveSet *pset,
                               const osg::Array *vx,
                               const osg::Array *nx,
                               const osg::Array *tx,
                               const osg::IndexArray *vix,
                               const osg::IndexArray *nix,
                               const osg::IndexArray *tix,
                               int iA, int iB, int iC);

private:
    osg::ref_ptr<osg::Vec4Array> T_;
    osg::ref_ptr<osg::Vec4Array> B_;
    osg::ref_ptr<osg::Vec4Array> N_;
    osg::ref_ptr<osg::UIntArray> indices_;
};

}

#endif
