/* OpenSceneGraph example, osgshadow.
*
*  Permission is hereby granted, free of charge, to any person obtaining a copy
*  of this software and associated documentation files (the "Software"), to deal
*  in the Software without restriction, including without limitation the rights
*  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
*  copies of the Software, and to permit persons to whom the Software is
*  furnished to do so, subject to the following conditions:
*
*  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
*  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
*  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
*  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
*  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
*  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
*  THE SOFTWARE.
*/

/* ##################################################################################################### */
/* ParallelSplitShadowMap written by Adrian Egli (3dhelp (at) gmail.com)                                   */
/* ##################################################################################################### */
/*                                                                                                         */
/* the pssm main idea is based on:                                                                            */
/*                                                                                                         */
/* Parallel-Split Shadow Maps for Large-scale Virtual Environments                                         */
/*    Fan Zhang     Hanqiu Sun    Leilei Xu    Lee Kit Lun                                                 */
/*    The Chinese University of Hong Kong                                                                 */
/*                                                                                                         */
/* Refer to our latest project webpage for "Parallel-Split Shadow Maps on Programmable GPUs" in GPU Gems */
/*                                                                                                         */
/* ##################################################################################################### */

#include <osgShadow/ParallelSplitShadowMap>

#include <osgShadow/ShadowedScene>
#include <osg/Notify>
#include <osg/ComputeBoundsVisitor>
#include <osg/PolygonOffset>
#include <osg/CullFace>
#include <osg/io_utils>
#include <iostream>
#include <sstream>
#include <osg/Geode>
#include <osg/Geometry>
#include <osgDB/ReadFile>
#include <osg/Texture1D>
#include <osg/Depth>
#include <osg/ShadeModel>

using namespace osgShadow;

// split scheme
#define TEXTURE_RESOLUTION  1024




#define ZNEAR_MIN_FROM_LIGHT_SOURCE 5.0
#define MOVE_VIRTUAL_CAMERA_BEHIND_REAL_CAMERA_FACTOR 0.0

//#define SHOW_SHADOW_TEXTURE_DEBUG    // DEPTH instead of color for debug information texture display in a rectangle
//#define SHADOW_TEXTURE_DEBUG         // COLOR instead of DEPTH

#ifndef SHADOW_TEXTURE_DEBUG
#define SHADOW_TEXTURE_GLSL
#endif

//////////////////////////////////////////////////////////////////////////
// FragmentShaderGenerator
std::string ParallelSplitShadowMap::FragmentShaderGenerator::generateGLSL_FragmentShader_BaseTex(
    bool debug,
    unsigned int splitCount,
    double textureRes,
    bool filtered,
    unsigned int nbrSplits,
    unsigned int textureOffset
    ) {
        std::stringstream sstr;

        /// base texture
        sstr << "uniform sampler2D baseTexture; "      << std::endl;
        sstr << "uniform float enableBaseTexture; "     << std::endl;
        sstr << "uniform vec2 ambientBias;"    << std::endl;

        for (unsigned int i=0;i<nbrSplits;i++)    {
            sstr << "uniform sampler2DShadow shadowTexture"    <<    i    <<"; "    << std::endl;
            sstr << "uniform float zShadow"                    <<    i    <<"; "    << std::endl;
        }




        sstr << "void main(void)"    << std::endl;
        sstr << "{"    << std::endl;


        /// select the shadow map : split
        sstr << "float testZ = gl_FragCoord.z*2.0-1.0;" <<std::endl;
        sstr << "float map0 = step(testZ, zShadow0);"<< std::endl;//DEBUG
        for (unsigned int i=1;i<nbrSplits;i++)    {
            sstr << "float map" << i << "  = step(zShadow"<<i-1<<",testZ)*step(testZ, zShadow"<<i<<");"<< std::endl;//DEBUG
        }

        if (filtered) {
            sstr << "          float fTexelSize="<< (1.41 / textureRes ) <<";" << std::endl;
            sstr << "          float fZOffSet  = -0.001954;" << std::endl; // 2^-9 good value for ATI / NVidia

        }
        for (unsigned int i=0;i<nbrSplits;i++)    {
            if (!filtered) {
                sstr << "    float shadow"    <<    i    <<" = shadow2DProj( shadowTexture"    <<    i    <<",gl_TexCoord["    <<    (i+textureOffset)    <<"]).r;"   << std::endl;
                sstr << " shadow"    <<    i    <<" = step(0.25,shadow"    <<    i    <<");" << std::endl; // reduce shadow artefacts
            } else {


                // filter the shadow (look up) 3x3 
                //
                // 1 0 1
                // 0 2 0 
                // 1 0 1 
                //
                // / 6

                sstr << "    float shadowOrg"    <<    i    <<" = shadow2DProj( shadowTexture"  <<    i    <<",gl_TexCoord["    <<    (i+textureOffset)    <<"]+vec4(0.0,0.0,fZOffSet,0.0) ).r;"   << std::endl;
                sstr << "    float shadow0"    <<    i    <<" = shadow2DProj( shadowTexture"    <<    i    <<",gl_TexCoord["    <<    (i+textureOffset)    <<"]+vec4(-fTexelSize,-fTexelSize,fZOffSet,0.0) ).r;"   << std::endl;
                sstr << "    float shadow1"    <<    i    <<" = shadow2DProj( shadowTexture"    <<    i    <<",gl_TexCoord["    <<    (i+textureOffset)    <<"]+vec4( fTexelSize,-fTexelSize,fZOffSet,0.0) ).r;"   << std::endl;
                sstr << "    float shadow2"    <<    i    <<" = shadow2DProj( shadowTexture"    <<    i    <<",gl_TexCoord["    <<    (i+textureOffset)    <<"]+vec4( fTexelSize, fTexelSize,fZOffSet,0.0) ).r;"   << std::endl;
                sstr << "    float shadow3"    <<    i    <<" = shadow2DProj( shadowTexture"    <<    i    <<",gl_TexCoord["    <<    (i+textureOffset)    <<"]+vec4(-fTexelSize, fTexelSize,fZOffSet,0.0) ).r;"   << std::endl;

                sstr << "    float shadow"    <<    i    <<" = ( 2.0*shadowOrg"    <<    i    
                    <<" + shadow0"    <<    i  
                    <<" + shadow1"    <<    i  
                    <<" + shadow2"    <<    i  
                    <<" + shadow3"    <<    i  
                    << ")/6.0;"<< std::endl;

                //sstr << " shadow"    <<    i    <<" = shadow"    <<    i    <<" * step(0.025,shadow"    <<    i    <<");" << std::endl; // reduce shadow artefacts

                //sstr << "    float shadow02"    <<    i    <<" = (shadow0"    <<    i    <<"+shadow2"    <<    i    <<")*0.5;"<< std::endl;
                //sstr << "    float shadow13"    <<    i    <<" = (shadow1"    <<    i    <<"+shadow3"    <<    i    <<")*0.5;"<< std::endl;
                //sstr << "    float shadowSoft"    <<    i    <<" = (shadow02"    <<    i    <<"+shadow13"    <<    i    <<")*0.5;"<< std::endl;
                //sstr << "    float shadow"    <<    i    <<" = (shadowSoft"    <<    i    <<"+shadowOrg"    <<    i    <<")*0.5;"<< std::endl;
                //sstr << " shadow"    <<    i    <<" = step(0.25,shadow"    <<    i    <<");" << std::endl; // reduce shadow artefacts
            }
        }


        sstr << "    float term0 = (1.0-shadow0)*map0; "    << std::endl;
        for (unsigned int i=1;i<nbrSplits;i++)    {
            sstr << "    float term" << i << " = map"<< i << "*(1.0-shadow"<<i<<");"<< std::endl;
        }



        /// build shadow factor value v
        sstr << "    float v = clamp(";
        for (unsigned int i=0;i<nbrSplits;i++)    {
            sstr << "term"    <<    i;
            if ( i+1 < nbrSplits ){
                sstr << "+";
            }
        }
        sstr << ",0.0,1.0);"    << std::endl;




        if ( debug ) {


            sstr << "    float c0=0.0;" << std::endl;
            sstr << "    float c1=0.0;" << std::endl;
            sstr << "    float c2=0.0;" << std::endl;

            sstr << "    float sumTerm=0.0;" << std::endl;

            for (unsigned int i=0;i<nbrSplits;i++)    {
                if ( i < 3 ) sstr << "    c" << i << "=term" << i << ";" << std::endl;
                sstr << "    sumTerm=sumTerm+term" << i << ";" << std::endl;
            }

            sstr << "    vec4 color    = gl_Color*( 1.0 - sumTerm ) + (sumTerm)* gl_Color*vec4(c0,(1.0-c0)*c1,(1.0-c0)*(1.0-c1)*c2,1.0); "    << std::endl;


            switch(nbrSplits){
            case 1: sstr << "    color    =  color*0.75 + vec4(map0,0,0,1.0)*0.25; "    << std::endl;break;
            case 2: sstr << "    color    =  color*0.75 + vec4(map0,map1,0,1.0)*0.25; "    << std::endl;break;
            case 3: sstr << "    color    =  color*0.75 + vec4(map0,map1,map2,1.0)*0.25; "    << std::endl; break;
            case 4: sstr << "    color    =  color*0.75 + vec4(map0+map3,map1+map3,map2,1.0)*0.25; "    << std::endl; break;
            case 5: sstr << "    color    =  color*0.75 + vec4(map0+map3,map1+map3+map4,map2+map4,1.0)*0.25; "    << std::endl;break;
            case 6: sstr << "    color    =  color*0.75 + vec4(map0+map3+map5,map1+map3+map4,map2+map4+map5,1.0)*0.25; "    << std::endl;    break;
            default: break;
            }


        } else {
            sstr << "    vec4 color    = gl_Color; "<< std::endl;
        }







        sstr << "    vec4 texcolor = texture2D(baseTexture,gl_TexCoord[0].st); "    << std::endl;


        sstr << "    float enableBaseTextureFilter = enableBaseTexture*(1.0 - step(texcolor.x+texcolor.y+texcolor.z+texcolor.a,0.0)); "    << std::endl;                                                //18
        sstr << "    vec4 colorTex = color*texcolor;" << std::endl;
        sstr << "    gl_FragColor.rgb = (((color*(ambientBias.x+1.0)*(1.0-enableBaseTextureFilter)) + colorTex*(1.0+ambientBias.x)*enableBaseTextureFilter)*(1.0-ambientBias.y*v)).rgb; "<< std::endl;
        sstr << "    gl_FragColor.a = (color*(1.0-enableBaseTextureFilter) + colorTex*enableBaseTextureFilter).a; "<< std::endl;



        sstr << "}"<< std::endl;

        //std::cout << sstr.str() << std::endl;
        if ( splitCount == nbrSplits-1 ) { OSG_INFO << std::endl << "ParallelSplitShadowMap: GLSL shader code:" << std::endl << "-------------------------------------------------------------------"  << std::endl << sstr.str() << std::endl; }

        return sstr.str();
}

//////////////////////////////////////////////////////////////////////////
// clamp variables of any type
template<class Type> inline Type Clamp(Type A, Type Min, Type Max) {
    if(A<Min) return Min;
    if(A>Max) return Max;
    return A;
}

#define min(a,b)            (((a) < (b)) ? (a) : (b))
#define max(a,b)            (((a) > (b)) ? (a) : (b))

//////////////////////////////////////////////////////////////////////////
ParallelSplitShadowMap::ParallelSplitShadowMap(osg::Geode** gr, int icountplanes) :
    _textureUnitOffset(1),
    _debug_color_in_GLSL(false),
    _user_polgyonOffset_set(false),
    _resolution(TEXTURE_RESOLUTION),
    _isSetMaxFarDistance(false),
    _split_min_near_dist(ZNEAR_MIN_FROM_LIGHT_SOURCE),
    _move_vcam_behind_rcam_factor(MOVE_VIRTUAL_CAMERA_BEHIND_REAL_CAMERA_FACTOR),
    _userLight(NULL),
    _GLSL_shadow_filtered(true),
    _ambientBiasUniform(NULL),
    _ambientBias(0.1f,0.3f)
{
    _displayTexturesGroupingNode = gr;
    _number_of_splits = icountplanes;

    _polgyonOffset.set(0.0f,0.0f);
    setFragmentShaderGenerator(new FragmentShaderGenerator());
    setSplitCalculationMode(SPLIT_EXP);
}

ParallelSplitShadowMap::ParallelSplitShadowMap(const ParallelSplitShadowMap& copy, const osg::CopyOp& copyop):
    ShadowTechnique(copy,copyop),
    _textureUnitOffset(copy._textureUnitOffset),
    _number_of_splits(copy._number_of_splits),
    _debug_color_in_GLSL(copy._debug_color_in_GLSL),
    _polgyonOffset(copy._polgyonOffset),
    _user_polgyonOffset_set(copy._user_polgyonOffset_set),
    _resolution(copy._resolution),
    _setMaxFarDistance(copy._setMaxFarDistance),
    _isSetMaxFarDistance(copy._isSetMaxFarDistance),
    _split_min_near_dist(copy._split_min_near_dist),
    _move_vcam_behind_rcam_factor(copy._move_vcam_behind_rcam_factor),
    _userLight(copy._userLight),
    _FragmentShaderGenerator(copy._FragmentShaderGenerator),
    _GLSL_shadow_filtered(copy._GLSL_shadow_filtered),
    _SplitCalcMode(copy._SplitCalcMode),
    _ambientBiasUniform(NULL),
    _ambientBias(copy._ambientBias)
{
}

void ParallelSplitShadowMap::setAmbientBias(const osg::Vec2& ambientBias)
{
    _ambientBias = ambientBias;
    if (_ambientBiasUniform ) _ambientBiasUniform->set(osg::Vec2f(_ambientBias.x(), _ambientBias.y()));
}

void ParallelSplitShadowMap::init(){
    if (!_shadowedScene) return;

    osg::StateSet* sharedStateSet = new osg::StateSet;


    unsigned int iCamerasMax=_number_of_splits;
    for (unsigned int iCameras=0;iCameras<iCamerasMax;iCameras++)
    {
        PSSMShadowSplitTexture pssmShadowSplitTexture;
        pssmShadowSplitTexture._splitID = iCameras;
        pssmShadowSplitTexture._textureUnit = iCameras+_textureUnitOffset;

        pssmShadowSplitTexture._resolution = _resolution;

        OSG_DEBUG << "ParallelSplitShadowMap : Texture ID=" << iCameras << " Resolution=" << pssmShadowSplitTexture._resolution << std::endl;
        // set up the texture to render into
        {
            pssmShadowSplitTexture._texture = new osg::Texture2D;
            pssmShadowSplitTexture._texture->setTextureSize(pssmShadowSplitTexture._resolution, pssmShadowSplitTexture._resolution);
#ifndef SHADOW_TEXTURE_DEBUG
            pssmShadowSplitTexture._texture->setInternalFormat(GL_DEPTH_COMPONENT);
            pssmShadowSplitTexture._texture->setShadowComparison(true);
            pssmShadowSplitTexture._texture->setShadowTextureMode(osg::Texture2D::LUMINANCE);
#else
            pssmShadowSplitTexture._texture->setInternalFormat(GL_RGBA);
#endif
            pssmShadowSplitTexture._texture->setFilter(osg::Texture2D::MIN_FILTER,osg::Texture2D::NEAREST);
            pssmShadowSplitTexture._texture->setFilter(osg::Texture2D::MAG_FILTER,osg::Texture2D::NEAREST);
            pssmShadowSplitTexture._texture->setBorderColor(osg::Vec4(1.0,1.0,1.0,1.0));
            pssmShadowSplitTexture._texture->setWrap(osg::Texture2D::WRAP_S, osg::Texture2D::CLAMP_TO_BORDER);
            pssmShadowSplitTexture._texture->setWrap(osg::Texture2D::WRAP_T, osg::Texture2D::CLAMP_TO_BORDER);
        }
        // set up the render to texture camera.
        {
            // create the camera
            pssmShadowSplitTexture._camera = new osg::Camera;
            pssmShadowSplitTexture._camera->setCullCallback(new CameraCullCallback(this));


#ifndef SHADOW_TEXTURE_DEBUG
            pssmShadowSplitTexture._camera->setClearMask(GL_DEPTH_BUFFER_BIT);
            pssmShadowSplitTexture._camera->setClearColor(osg::Vec4(1.0,1.0,1.0,1.0));
#else
            pssmShadowSplitTexture._camera->setClearMask(GL_DEPTH_BUFFER_BIT|GL_COLOR_BUFFER_BIT);
            switch(iCameras)
            {
            case 0:
                pssmShadowSplitTexture._camera->setClearColor(osg::Vec4(1.0,0.0,0.0,1.0));
                break;
            case 1:
                pssmShadowSplitTexture._camera->setClearColor(osg::Vec4(0.0,1.0,0.0,1.0));
                break;
            case 2:
                pssmShadowSplitTexture._camera->setClearColor(osg::Vec4(0.0,0.0,1.0,1.0));
                break;
            default:
                pssmShadowSplitTexture._camera->setClearColor(osg::Vec4(1.0,1.0,1.0,1.0));
                break;
            }
#endif
            pssmShadowSplitTexture._camera->setComputeNearFarMode(osg::Camera::DO_NOT_COMPUTE_NEAR_FAR);
            pssmShadowSplitTexture._camera->setReferenceFrame(osg::Camera::ABSOLUTE_RF_INHERIT_VIEWPOINT);

            // set viewport
            pssmShadowSplitTexture._camera->setViewport(0,0,pssmShadowSplitTexture._resolution,pssmShadowSplitTexture._resolution);

            // set the camera to render before the main camera.
            pssmShadowSplitTexture._camera->setRenderOrder(osg::Camera::PRE_RENDER);

            // tell the camera to use OpenGL frame buffer object where supported.
            pssmShadowSplitTexture._camera->setRenderTargetImplementation(osg::Camera::FRAME_BUFFER_OBJECT);

            // attach the texture and use it as the color buffer.
#ifndef SHADOW_TEXTURE_DEBUG
            pssmShadowSplitTexture._camera->attach(osg::Camera::DEPTH_BUFFER, pssmShadowSplitTexture._texture.get());
#else
            pssmShadowSplitTexture._camera->attach(osg::Camera::COLOR_BUFFER, pssmShadowSplitTexture._texture.get());
#endif
            osg::StateSet* stateset = pssmShadowSplitTexture._camera->getOrCreateStateSet();



            //////////////////////////////////////////////////////////////////////////
            if ( _user_polgyonOffset_set ) {
                float factor = _polgyonOffset.x();
                float units  = _polgyonOffset.y();
                osg::ref_ptr<osg::PolygonOffset> polygon_offset = new osg::PolygonOffset;
                polygon_offset->setFactor(factor);
                polygon_offset->setUnits(units);
                stateset->setAttribute(polygon_offset.get(), osg::StateAttribute::ON | osg::StateAttribute::OVERRIDE);
                stateset->setMode(GL_POLYGON_OFFSET_FILL, osg::StateAttribute::ON | osg::StateAttribute::OVERRIDE);
            }           


            //////////////////////////////////////////////////////////////////////////
            if ( ! _GLSL_shadow_filtered ) {
                // if not glsl filtering enabled then we should force front face culling to reduce the number of shadow artefacts.
                osg::ref_ptr<osg::CullFace> cull_face = new osg::CullFace;
                cull_face->setMode(osg::CullFace::FRONT);
                stateset->setAttribute(cull_face.get(), osg::StateAttribute::ON | osg::StateAttribute::OVERRIDE);
                stateset->setMode(GL_CULL_FACE, osg::StateAttribute::ON | osg::StateAttribute::OVERRIDE);
            }

            //////////////////////////////////////////////////////////////////////////
            osg::ShadeModel* shademodel = dynamic_cast<osg::ShadeModel*>(stateset->getAttribute(osg::StateAttribute::SHADEMODEL));
            if (!shademodel){shademodel = new osg::ShadeModel;stateset->setAttribute(shademodel);}
            shademodel->setMode( osg::ShadeModel::FLAT );
            stateset->setMode(GL_LIGHTING,osg::StateAttribute::OFF);
        }

        //////////////////////////////////////////////////////////////////////////
        // set up stateset and append texture, texGen ,...
        {
            pssmShadowSplitTexture._stateset = sharedStateSet;//new osg::StateSet;
            pssmShadowSplitTexture._stateset->setTextureAttributeAndModes(pssmShadowSplitTexture._textureUnit,pssmShadowSplitTexture._texture.get(),osg::StateAttribute::ON | osg::StateAttribute::OVERRIDE);
            pssmShadowSplitTexture._stateset->setTextureMode(pssmShadowSplitTexture._textureUnit,GL_TEXTURE_GEN_S,osg::StateAttribute::ON);
            pssmShadowSplitTexture._stateset->setTextureMode(pssmShadowSplitTexture._textureUnit,GL_TEXTURE_GEN_T,osg::StateAttribute::ON);
            pssmShadowSplitTexture._stateset->setTextureMode(pssmShadowSplitTexture._textureUnit,GL_TEXTURE_GEN_R,osg::StateAttribute::ON);
            pssmShadowSplitTexture._stateset->setTextureMode(pssmShadowSplitTexture._textureUnit,GL_TEXTURE_GEN_Q,osg::StateAttribute::ON);


            /// generate a TexGen object
            pssmShadowSplitTexture._texgen = new osg::TexGen;

        }

        //////////////////////////////////////////////////////////////////////////
        // set up shader (GLSL)
#ifdef SHADOW_TEXTURE_GLSL

        osg::Program* program = new osg::Program;
        pssmShadowSplitTexture._stateset->setAttribute(program);

        //////////////////////////////////////////////////////////////////////////
        // GLSL PROGRAMS
        osg::Shader* fragment_shader = new osg::Shader(osg::Shader::FRAGMENT,
            _FragmentShaderGenerator->generateGLSL_FragmentShader_BaseTex(
            _debug_color_in_GLSL,
            iCameras,
            pssmShadowSplitTexture._resolution,
            _GLSL_shadow_filtered,
            _number_of_splits,
            _textureUnitOffset
            ).c_str());
        program->addShader(fragment_shader);


        //////////////////////////////////////////////////////////////////////////
        // UNIFORMS
        std::stringstream strST; strST << "shadowTexture" << (pssmShadowSplitTexture._textureUnit-_textureUnitOffset);
        osg::Uniform* shadowTextureSampler = new osg::Uniform(strST.str().c_str(),(int)(pssmShadowSplitTexture._textureUnit));
        pssmShadowSplitTexture._stateset->addUniform(shadowTextureSampler);

        //TODO: NOT YET SUPPORTED in the current version of the shader
        if ( ! _ambientBiasUniform ) {
            _ambientBiasUniform = new osg::Uniform("ambientBias",_ambientBias);
            pssmShadowSplitTexture._stateset->addUniform(_ambientBiasUniform);
        }


        std::stringstream strzShadow; strzShadow << "zShadow" << (pssmShadowSplitTexture._textureUnit-_textureUnitOffset);
        pssmShadowSplitTexture._farDistanceSplit = new osg::Uniform(strzShadow.str().c_str(),1.0f);
        pssmShadowSplitTexture._stateset->addUniform(pssmShadowSplitTexture._farDistanceSplit);

        osg::Uniform* baseTextureSampler = new osg::Uniform("baseTexture",0);
        pssmShadowSplitTexture._stateset->addUniform(baseTextureSampler);

        osg::Uniform* randomTextureSampler = new osg::Uniform("randomTexture",(int)(_textureUnitOffset+_number_of_splits));
        pssmShadowSplitTexture._stateset->addUniform(randomTextureSampler);

        if ( _textureUnitOffset > 0 ) {
            osg::Uniform* enableBaseTexture = new osg::Uniform("enableBaseTexture",1.0f);
            pssmShadowSplitTexture._stateset->addUniform(enableBaseTexture);
        } else {
            osg::Uniform* enableBaseTexture = new osg::Uniform("enableBaseTexture",0.0f);
            pssmShadowSplitTexture._stateset->addUniform(enableBaseTexture);
        }

        for (unsigned int textLoop(0);textLoop<_textureUnitOffset;textLoop++)
        {
            // fake texture for baseTexture, add a fake texture
            // we support by default at least one texture layer
            // without this fake texture we can not support
            // textured and not textured scene

            // TODO: at the moment the PSSM supports just one texture layer in the GLSL shader, multitexture are
            //       not yet supported !

            osg::Image* image = new osg::Image;
            // allocate the image data, noPixels x 1 x 1 with 4 rgba floats - equivalent to a Vec4!
            int noPixels = 1;
            image->allocateImage(noPixels,1,1,GL_RGBA,GL_FLOAT);
            image->setInternalTextureFormat(GL_RGBA);
            // fill in the image data.
            osg::Vec4* dataPtr = (osg::Vec4*)image->data();
            osg::Vec4f color(1.0f,1.0f,1.0f,0.0f);
            *dataPtr = color;
            // make fake texture
            osg::Texture2D* texture = new osg::Texture2D;
            texture->setWrap(osg::Texture2D::WRAP_S,osg::Texture2D::CLAMP_TO_BORDER);
            texture->setWrap(osg::Texture2D::WRAP_T,osg::Texture2D::CLAMP_TO_BORDER);
            texture->setBorderColor(osg::Vec4(1.0,1.0,1.0,1.0));
            texture->setFilter(osg::Texture2D::MIN_FILTER,osg::Texture2D::LINEAR);
            texture->setFilter(osg::Texture2D::MAG_FILTER,osg::Texture2D::LINEAR);
            texture->setImage(image);
            // add fake texture
            pssmShadowSplitTexture._stateset->setTextureAttribute(textLoop,texture,osg::StateAttribute::ON);
            pssmShadowSplitTexture._stateset->setTextureMode(textLoop,GL_TEXTURE_1D,osg::StateAttribute::OFF);
            pssmShadowSplitTexture._stateset->setTextureMode(textLoop,GL_TEXTURE_2D,osg::StateAttribute::ON);
            pssmShadowSplitTexture._stateset->setTextureMode(textLoop,GL_TEXTURE_3D,osg::StateAttribute::OFF);
        }
#endif


        //////////////////////////////////////////////////////////////////////////
        // DEBUG
        if ( _displayTexturesGroupingNode ) {
            {
                pssmShadowSplitTexture._debug_textureUnit = 1;
                pssmShadowSplitTexture._debug_texture = new osg::Texture2D;
                pssmShadowSplitTexture._debug_texture->setTextureSize(TEXTURE_RESOLUTION, TEXTURE_RESOLUTION);
#ifdef SHOW_SHADOW_TEXTURE_DEBUG
                pssmShadowSplitTexture._debug_texture->setInternalFormat(GL_DEPTH_COMPONENT);
                pssmShadowSplitTexture._debug_texture->setShadowTextureMode(osg::Texture2D::LUMINANCE);
#else
                pssmShadowSplitTexture._debug_texture->setInternalFormat(GL_RGBA);
#endif
                pssmShadowSplitTexture._debug_texture->setFilter(osg::Texture2D::MIN_FILTER,osg::Texture2D::LINEAR);
                pssmShadowSplitTexture._debug_texture->setFilter(osg::Texture2D::MAG_FILTER,osg::Texture2D::LINEAR);
                // create the camera
                pssmShadowSplitTexture._debug_camera = new osg::Camera;
                pssmShadowSplitTexture._debug_camera->setCullCallback(new CameraCullCallback(this));
                pssmShadowSplitTexture._debug_camera->setClearMask(GL_DEPTH_BUFFER_BIT|GL_COLOR_BUFFER_BIT);
                pssmShadowSplitTexture._debug_camera->setClearColor(osg::Vec4(1.0,1.0,1.0,1.0));
                pssmShadowSplitTexture._debug_camera->setComputeNearFarMode(osg::Camera::DO_NOT_COMPUTE_NEAR_FAR);

                // set viewport
                pssmShadowSplitTexture._debug_camera->setViewport(0,0,TEXTURE_RESOLUTION,TEXTURE_RESOLUTION);
                // set the camera to render before the main camera.
                pssmShadowSplitTexture._debug_camera->setRenderOrder(osg::Camera::PRE_RENDER);
                // tell the camera to use OpenGL frame buffer object where supported.
                pssmShadowSplitTexture._debug_camera->setRenderTargetImplementation(osg::Camera::FRAME_BUFFER_OBJECT);
                // attach the texture and use it as the color buffer.
#ifdef SHOW_SHADOW_TEXTURE_DEBUG
                pssmShadowSplitTexture._debug_camera->attach(osg::Camera::DEPTH_BUFFER, pssmShadowSplitTexture._debug_texture.get());
#else
                pssmShadowSplitTexture._debug_camera->attach(osg::Camera::COLOR_BUFFER, pssmShadowSplitTexture._debug_texture.get());
#endif
                // osg::StateSet* stateset = pssmShadowSplitTexture._debug_camera->getOrCreateStateSet();

                pssmShadowSplitTexture._debug_stateset = new osg::StateSet;
                pssmShadowSplitTexture._debug_stateset->setTextureAttributeAndModes(pssmShadowSplitTexture._debug_textureUnit,pssmShadowSplitTexture._debug_texture.get(),osg::StateAttribute::ON | osg::StateAttribute::OVERRIDE);
                pssmShadowSplitTexture._debug_stateset->setTextureMode(pssmShadowSplitTexture._debug_textureUnit,GL_TEXTURE_GEN_S,osg::StateAttribute::ON);
                pssmShadowSplitTexture._debug_stateset->setTextureMode(pssmShadowSplitTexture._debug_textureUnit,GL_TEXTURE_GEN_T,osg::StateAttribute::ON);
                pssmShadowSplitTexture._debug_stateset->setTextureMode(pssmShadowSplitTexture._debug_textureUnit,GL_TEXTURE_GEN_R,osg::StateAttribute::ON);
                pssmShadowSplitTexture._debug_stateset->setTextureMode(pssmShadowSplitTexture._debug_textureUnit,GL_TEXTURE_GEN_Q,osg::StateAttribute::ON);
            }

            osg::Geode* geode = _displayTexturesGroupingNode[iCameras];
            geode->getOrCreateStateSet()->setTextureAttributeAndModes(0,pssmShadowSplitTexture._debug_texture.get(),osg::StateAttribute::ON);

        }
        //////////////////////////////////////////////////////////////////////////

        _PSSMShadowSplitTextureMap.insert(PSSMShadowSplitTextureMap::value_type(iCameras,pssmShadowSplitTexture));


    }


    _dirty = false;
}

void ParallelSplitShadowMap::update(osg::NodeVisitor& nv){
    getShadowedScene()->osg::Group::traverse(nv);
}

void ParallelSplitShadowMap::cull(osgUtil::CullVisitor& cv){
    // record the traversal mask on entry so we can reapply it later.
    unsigned int traversalMask = cv.getTraversalMask();
    osgUtil::RenderStage* orig_rs = cv.getRenderStage();

    // do traversal of shadow receiving scene which does need to be decorated by the shadow map
    for (PSSMShadowSplitTextureMap::iterator it=_PSSMShadowSplitTextureMap.begin();it!=_PSSMShadowSplitTextureMap.end();it++)
    {
        PSSMShadowSplitTexture pssmShadowSplitTexture = it->second;
        cv.pushStateSet(pssmShadowSplitTexture._stateset.get());

        //////////////////////////////////////////////////////////////////////////
        // DEBUG
        if ( _displayTexturesGroupingNode ) {
            cv.pushStateSet(pssmShadowSplitTexture._debug_stateset.get());
        }
        //////////////////////////////////////////////////////////////////////////

        _shadowedScene->osg::Group::traverse(cv);

        cv.popStateSet();

    }

    // need to compute view frustum for RTT camera.
    // get the bounds of the model.
    osg::ComputeBoundsVisitor cbbv(osg::NodeVisitor::TRAVERSE_ACTIVE_CHILDREN);
    cbbv.setTraversalMask(getShadowedScene()->getCastsShadowTraversalMask());
    _shadowedScene->osg::Group::traverse(cbbv);
    osg::BoundingBox bb = cbbv.getBoundingBox();
    //////////////////////////////////////////////////////////////////////////
    const osg::Light* selectLight = 0;

    /// light pos and light direction
    osg::Vec4 lightpos;
    osg::Vec3 lightDirection;

    if ( ! _userLight ) {
        // try to find a light in the scene
        osgUtil::PositionalStateContainer::AttrMatrixList& aml = orig_rs->getPositionalStateContainer()->getAttrMatrixList();
        for(osgUtil::PositionalStateContainer::AttrMatrixList::iterator itr = aml.begin();
            itr != aml.end();
            ++itr)
        {
            const osg::Light* light = dynamic_cast<const osg::Light*>(itr->first.get());
            if (light)
            {
                osg::RefMatrix* matrix = itr->second.get();
                if (matrix) lightpos = light->getPosition() * (*matrix);
                else lightpos = light->getPosition();
                if (matrix) lightDirection = light->getDirection() * (*matrix);
                else lightDirection = light->getDirection();

                selectLight = light;
            }
        }

        osg::Matrix eyeToWorld;
        eyeToWorld.invert(*cv.getModelViewMatrix());

        lightpos = lightpos * eyeToWorld;
        lightDirection = lightDirection * eyeToWorld;
    }else{
        // take the user light as light source
        lightpos = _userLight->getPosition();
        lightDirection = _userLight->getDirection();
        selectLight = _userLight.get();
    }

    if (selectLight)
    {

        // do traversal of shadow receiving scene which does need to be decorated by the shadow map
        //unsigned int iMaxSplit = _PSSMShadowSplitTextureMap.size();

        for (PSSMShadowSplitTextureMap::iterator it=_PSSMShadowSplitTextureMap.begin();it!=_PSSMShadowSplitTextureMap.end();it++)
        {
            PSSMShadowSplitTexture pssmShadowSplitTexture = it->second;


            //////////////////////////////////////////////////////////////////////////
            // SETUP pssmShadowSplitTexture for rendering
            //
            lightDirection.normalize();
            pssmShadowSplitTexture._lightDirection = lightDirection;
            pssmShadowSplitTexture._cameraView    = cv.getRenderInfo().getView()->getCamera()->getViewMatrix();
            pssmShadowSplitTexture._cameraProj    = cv.getRenderInfo().getView()->getCamera()->getProjectionMatrix();

            //////////////////////////////////////////////////////////////////////////
            // CALCULATE



            // Calculate corner points of frustum split
            //
            // To avoid edge problems, scale the frustum so
            // that it's at least a few pixels larger
            //
            osg::Vec3d pCorners[8];
            calculateFrustumCorners(pssmShadowSplitTexture,pCorners);

            // Init Light (Directional Light)
            //
            calculateLightInitialPosition(pssmShadowSplitTexture,pCorners);

            // Calculate near and far for light view
            //
            calculateLightNearFarFormFrustum(pssmShadowSplitTexture,pCorners);

            // Calculate view and projection matrices
            //
            calculateLightViewProjectionFormFrustum(pssmShadowSplitTexture,pCorners);

            //////////////////////////////////////////////////////////////////////////
            // set up shadow rendering camera
            pssmShadowSplitTexture._camera->setReferenceFrame(osg::Camera::ABSOLUTE_RF);

            //////////////////////////////////////////////////////////////////////////
            // DEBUG
            if ( _displayTexturesGroupingNode ) {
                pssmShadowSplitTexture._debug_camera->setViewMatrix(pssmShadowSplitTexture._camera->getViewMatrix());
                pssmShadowSplitTexture._debug_camera->setProjectionMatrix(pssmShadowSplitTexture._camera->getProjectionMatrix());
                pssmShadowSplitTexture._debug_camera->setReferenceFrame(osg::Camera::ABSOLUTE_RF);
            }

            //////////////////////////////////////////////////////////////////////////
            // compute the matrix which takes a vertex from local coords into tex coords
            // will use this later to specify osg::TexGen..

            osg::Matrix MVPT = pssmShadowSplitTexture._camera->getViewMatrix() *
                pssmShadowSplitTexture._camera->getProjectionMatrix() *
                osg::Matrix::translate(1.0,1.0,1.0) *
                osg::Matrix::scale(0.5,0.5,0.5);

            pssmShadowSplitTexture._texgen->setMode(osg::TexGen::EYE_LINEAR);
            pssmShadowSplitTexture._texgen->setPlanesFromMatrix(MVPT);
            //////////////////////////////////////////////////////////////////////////


            //////////////////////////////////////////////////////////////////////////
            cv.setTraversalMask( traversalMask & getShadowedScene()->getCastsShadowTraversalMask() );

            // do RTT camera traversal
            pssmShadowSplitTexture._camera->accept(cv);

            //////////////////////////////////////////////////////////////////////////
            // DEBUG
            if ( _displayTexturesGroupingNode ) {
                pssmShadowSplitTexture._debug_camera->accept(cv);
            }


            orig_rs->getPositionalStateContainer()->addPositionedTextureAttribute(pssmShadowSplitTexture._textureUnit, cv.getModelViewMatrix(), pssmShadowSplitTexture._texgen.get());


        }
    } // if light



    // reapply the original traversal mask
    cv.setTraversalMask( traversalMask );
}

void ParallelSplitShadowMap::cleanSceneGraph(){

}


//////////////////////////////////////////////////////////////////////////
// Computes corner points of a frustum
//
//
//unit box representing frustum in clip space
const osg::Vec3f const_pointFarTR(1.0f, 1.0f, 1.0f);
const osg::Vec3f const_pointFarBR(1.0f, -1.0f, 1.0f);
const osg::Vec3f const_pointFarTL(-1.0f, 1.0f, 1.0f);
const osg::Vec3f const_pointFarBL(-1.0f, -1.0f, 1.0f);
const osg::Vec3f const_pointNearTR(1.0f, 1.0f, -1.0f);
const osg::Vec3f const_pointNearBR(1.0f, -1.0f, -1.0f);
const osg::Vec3f const_pointNearTL(-1.0f, 1.0f, -1.0f);
const osg::Vec3f const_pointNearBL(-1.0f, -1.0f, -1.0f);
//////////////////////////////////////////////////////////////////////////


void ParallelSplitShadowMap::calculateFrustumCorners(
    PSSMShadowSplitTexture &pssmShadowSplitTexture,
    osg::Vec3d *frustumCorners
    ) {

        // get user cameras
        double fovy,aspectRatio,camNear,camFar;
        pssmShadowSplitTexture._cameraProj.getPerspective(fovy,aspectRatio,camNear,camFar);


        // force to max far distance to show shadow, for some scene it can be solve performance problems.
        if ( _isSetMaxFarDistance ) {
            if (_setMaxFarDistance < camFar) camFar = _setMaxFarDistance;
        }


        // build camera matrix with some offsets (the user view camera)
        osg::Matrixf viewMat;
        osg::Vec3d camEye,camCenter,camUp;
        pssmShadowSplitTexture._cameraView.getLookAt(camEye,camCenter,camUp);
        osg::Vec3d viewDir = camCenter - camEye;
        //viewDir.normalize(); //we can assume that viewDir is still normalized in the viewMatrix
        camEye = camEye  - viewDir * _move_vcam_behind_rcam_factor;
        camFar += _move_vcam_behind_rcam_factor * viewDir.length();
        viewMat.makeLookAt(camEye,camCenter,camUp);



        //////////////////////////////////////////////////////////////////////////
        /// CALCULATE SPLIT
        double maxFar = camFar;
        // double minNear = camNear;
        double camNearFar_Dist = maxFar - camNear;
        if ( _SplitCalcMode == SPLIT_LINEAR ) {
            camFar  = camNear + (camNearFar_Dist) * ((double)(pssmShadowSplitTexture._splitID+1))/((double)(_number_of_splits));
            camNear = camNear + (camNearFar_Dist) * ((double)(pssmShadowSplitTexture._splitID))/((double)(_number_of_splits));
        } else {
            // Exponential split scheme:
            //
            // Ci = (n - f)*(i/numsplits)^(bias+1) + n;
            //
            static float fSplitSchemeBias[2]={0.25f,0.66f};
            fSplitSchemeBias[1]=Clamp(fSplitSchemeBias[1],0.0f,3.0f);
            float* pSplitDistances =new float[_number_of_splits+1];

            for(int i=0;i<(int)_number_of_splits;i++) {
                float fIDM=i/(float)_number_of_splits;
                pSplitDistances[i]=camNearFar_Dist*(powf(fIDM,fSplitSchemeBias[1]+1))+camNear;
            }
            // make sure border values are right
            pSplitDistances[0]=camNear;
            pSplitDistances[_number_of_splits]=camFar;

            camNear = pSplitDistances[pssmShadowSplitTexture._splitID];
            camFar  = pSplitDistances[pssmShadowSplitTexture._splitID+1];

            delete[] pSplitDistances;
        }


        pssmShadowSplitTexture._split_far = camFar;



        //////////////////////////////////////////////////////////////////////////
        /// TRANSFORM frustum corners (Optimized for Orthogonal)


        osg::Matrixf projMat;
        projMat.makePerspective(fovy,aspectRatio,camNear,camFar);
        osg::Matrixf projViewMat(viewMat*projMat);
        osg::Matrixf invProjViewMat;
        invProjViewMat.invert(projViewMat);

        //transform frustum vertices to world space
        frustumCorners[0] = const_pointFarBR * invProjViewMat;
        frustumCorners[1] = const_pointNearBR* invProjViewMat;
        frustumCorners[2] = const_pointNearTR* invProjViewMat;
        frustumCorners[3] = const_pointFarTR * invProjViewMat;
        frustumCorners[4] = const_pointFarTL * invProjViewMat;
        frustumCorners[5] = const_pointFarBL * invProjViewMat;
        frustumCorners[6] = const_pointNearBL* invProjViewMat;
        frustumCorners[7] = const_pointNearTL* invProjViewMat;

        //std::cout << "camFar : "<<pssmShadowSplitTexture._splitID << " / " << camNear << "," << camFar << std::endl;
}

//////////////////////////////////////////////////////////////////////////
//
// compute directional light initial position;
void ParallelSplitShadowMap::calculateLightInitialPosition(PSSMShadowSplitTexture &pssmShadowSplitTexture,osg::Vec3d *frustumCorners){
    pssmShadowSplitTexture._frustumSplitCenter = frustumCorners[0];
    for(int i=1;i<8;i++) {
        pssmShadowSplitTexture._frustumSplitCenter +=frustumCorners[i];
    }
    pssmShadowSplitTexture._frustumSplitCenter /= 8.0;


    //
    // To avoid edge problems, scale the frustum so
    // that it's at least a few pixels larger
    //
    for(int i=0;i<8;i++)
    {
        // scale by adding offset from center
        frustumCorners[i]+=(frustumCorners[i]-pssmShadowSplitTexture._frustumSplitCenter)*(0.75);
    }

}

void ParallelSplitShadowMap::calculateLightNearFarFormFrustum(
    PSSMShadowSplitTexture &pssmShadowSplitTexture,
    osg::Vec3d *frustumCorners
    ) {

        //calculate near, far
        double zFar(-DBL_MAX);

        // calculate zFar (as longest distance)
        for(int i=0;i<8;i++) {
            double dist_z_from_light = fabs(pssmShadowSplitTexture._lightDirection*(frustumCorners[i] -  pssmShadowSplitTexture._frustumSplitCenter));
            if ( zFar  < dist_z_from_light ) zFar  = dist_z_from_light;
        }

        // update camera position and look at center
        pssmShadowSplitTexture._lightCameraSource = pssmShadowSplitTexture._frustumSplitCenter - pssmShadowSplitTexture._lightDirection*(zFar+_split_min_near_dist);
        pssmShadowSplitTexture._lightCameraTarget = pssmShadowSplitTexture._frustumSplitCenter + pssmShadowSplitTexture._lightDirection*(zFar);

        // calculate [zNear,zFar]
        zFar = (-DBL_MAX);
        double zNear(DBL_MAX);
        for(int i=0;i<8;i++) {
            double dist_z_from_light = fabs(pssmShadowSplitTexture._lightDirection*(frustumCorners[i] -  pssmShadowSplitTexture._lightCameraSource));
            if ( zFar  < dist_z_from_light ) zFar  = dist_z_from_light;
            if ( zNear > dist_z_from_light ) zNear  = dist_z_from_light;
        }
        // update near - far plane
        pssmShadowSplitTexture._lightNear = max(zNear - _split_min_near_dist - 0.01,0.01);
        pssmShadowSplitTexture._lightFar  = zFar;
}




void ParallelSplitShadowMap::calculateLightViewProjectionFormFrustum(PSSMShadowSplitTexture &pssmShadowSplitTexture,osg::Vec3d *frustumCorners) {



    // calculate the camera's coordinate system
    osg::Vec3d camEye,camCenter,camUp;
    pssmShadowSplitTexture._cameraView.getLookAt(camEye,camCenter,camUp);
    osg::Vec3d viewDir(camCenter-camEye);
    osg::Vec3d camRight(camUp^viewDir);

    // we force to have normalized vectors (camera's view)
    camUp.normalize();
    viewDir.normalize();
    camRight.normalize();

    // use quaternion -> numerical more robust
    osg::Quat qRot;
    qRot.makeRotate(viewDir,pssmShadowSplitTexture._lightDirection);
    osg::Vec3d top =  qRot * camUp;
    osg::Vec3d right = qRot * camRight;

    // calculate the camera's frustum right,right,bottom,top parameters
    double maxRight(-DBL_MAX),maxTop(-DBL_MAX);
    double minRight(DBL_MAX),minTop(DBL_MAX);

    for(int i(0); i < 8; i++)
    {

        osg::Vec3d diffCorner(pssmShadowSplitTexture._lightCameraSource - frustumCorners[i]);
        double lright(diffCorner*right);
        double lTop(diffCorner*top);

        if ( lright > maxRight ) maxRight  =  lright;
        if ( lTop  > maxTop  ) maxTop   =  lTop;

        if ( lright < minRight ) minRight  =  lright;
        if ( lTop  < minTop  ) minTop   =  lTop;
    }

    // make the camera view matrix
    pssmShadowSplitTexture._camera->setViewMatrixAsLookAt(pssmShadowSplitTexture._lightCameraSource,pssmShadowSplitTexture._lightCameraTarget,top);

    // use ortho projection for light (directional light only supported)
    pssmShadowSplitTexture._camera->setProjectionMatrixAsOrtho(minRight,maxRight,minTop,maxTop,pssmShadowSplitTexture._lightNear,pssmShadowSplitTexture._lightFar);


#ifdef SHADOW_TEXTURE_GLSL
    // get user cameras
    osg::Vec3d vProjCamFraValue = (camEye + viewDir * pssmShadowSplitTexture._split_far) * (pssmShadowSplitTexture._cameraView * pssmShadowSplitTexture._cameraProj);
    pssmShadowSplitTexture._farDistanceSplit->set((float)vProjCamFraValue.z());
#endif


}



