/* -*- mode: c++; c-basic-offset: 4; indent-tabs-mode: nil -*- */
/*
 * Copyright (c) 2004-2013  HUBzero Foundation, LLC
 *
 */

#include <time.h>
#include <stdlib.h>
#include <stdio.h>
#include <math.h>
#include <pthread.h>

#include <GL/glew.h>
#include <Cg/cgGL.h>

#include <util/FilePath.h>

#include <Image.h>
#include <ImageLoader.h>
#include <ImageLoaderFactory.h>

#include <vrmath/Matrix4x4d.h>
#include <vrmath/Vector3f.h>
#include <vrmath/Vector4f.h>

#include "ParticleSystem.h"
#include "ParticleEmitter.h"
#include "Texture2D.h"
#include "Texture3D.h"
#include "Shader.h"
#include "Trace.h"

using namespace nv;
using namespace nv::util;

#define USE_RGBA_ARROW

//#define TEST

inline float randomRange(float rangeMin, float rangeMax)
{
    return ((float)rand() / RAND_MAX) * (rangeMax - rangeMin) + rangeMin ;
}

inline int logd(int value)
{
    int l;
    for (l = 0; value >> l; l++);
    return l - 1;
}

inline void swap(int& x, int& y)
{
    if (x != y) {
        x ^= y;
        y ^= x;
        x ^= y;
    }
}

void *ParticleSystem::dataLoadMain(void *data)
{
    ParticleSystem *particleSystem = (ParticleSystem *)data;
    CircularFifo<float*, 10>& queue = particleSystem->_queue;

    // TBD..
    //float min = particleSystem->_time_series_vel_mag_min;
    //float max = particleSystem->_time_series_vel_mag_max;

    int startIndex = particleSystem->_flowFileStartIndex;
    int endIndex = particleSystem->_flowFileEndIndex;

    int curIndex = startIndex;
    int flowWidth = particleSystem->_flowWidth;
    int flowHeight = particleSystem->_flowHeight;
    int flowDepth = particleSystem->_flowDepth;

    const char* fileNameFormat = particleSystem->_fileNameFormat.c_str();
    char buff[256];

    bool done = false;
    while (!done) {
        if (curIndex > endIndex) {
            curIndex = startIndex;
        }

        if (!queue.isFull()) {
            int tail = queue.tailIndex();
            if (tail != -1) {
                sprintf(buff, fileNameFormat, curIndex);
                //std::string path = FilePath::getInstance()->getPath(buff);
#ifdef WANT_TRACE
                float t = clock() /(float) CLOCKS_PER_SEC;
#endif
                LoadProcessedFlowRaw(buff, flowWidth, flowHeight, flowDepth, queue.array[tail]);
#ifdef WANT_TRACE
                float ti = clock() / (float) CLOCKS_PER_SEC;
                TRACE("LoadProcessedFlowRaw time: %f", ti - t);
#endif
                queue.push();
                TRACE("%d loaded", curIndex);
                ++curIndex;
            }
        }
    }

    return 0;
}

CGcontext ParticleSystem::_context = 0;

unsigned int SpotTexID = 0;

void MakeSphereTexture()
{
    const int DIM = 128;
    const int DIM2 = 63;
    //const float TEX_SCALE = 6.0;

    glGenTextures(1, (GLuint *)&SpotTexID);
    glBindTexture(GL_TEXTURE_2D, SpotTexID);

    float col[4] = {1.f, 1.f, 1.f, 1.f};
    glTexEnvfv(GL_TEXTURE_ENV, GL_TEXTURE_ENV_COLOR, col);
    glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_REPLACE);

    float *img = new float[DIM*DIM];

    vrmath::Vector3f light(1,1,3);
    light = light.normalize();

    for (int y = 0; y < DIM; y++) {
        for (int x = 0; x < DIM; x++) {
            // Clamping the edges to zero allows Nvidia's blend optimizations to do their thing.
            if (x == 0 || x == DIM-1 || y == 0 || y == DIM-1) {
                img[y*DIM+x] = 0;
            } else {
                vrmath::Vector3f p(x, y, 0);
                p = p - vrmath::Vector3f(DIM2, DIM2, 0);
                float len = p.length();
                float z = sqrt(DIM2*DIM2 - len*len);
                p.z = z;
                if (len >= DIM2) {
                    img[y*DIM+x] = 0.0;
                    continue;
                }

                p = p.normalize();
                float v = p.dot(light);
                if(v < 0) v = 0;

                img[y*DIM+x] = v;
            }
        }
    }

    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP);

    gluBuild2DMipmaps(GL_TEXTURE_2D, GL_ALPHA16, DIM, DIM, GL_ALPHA, GL_FLOAT, img);
}

//extern void algorithm_test(vrmath::Vector4f* data, int flowWidth, int flowHeight, int flowDepth);
//extern std::vector<vrmath::Vector3f>* find_critical_points(vrmath::Vector4f* data, int flowWidth, int flowHeight, int flowDepth);
ParticleSystem::ParticleSystem(int width, int height,
                               const std::string& fileName,
                               int fieldWidth, int fieldHeight, int fieldDepth, 
                               bool timeVaryingData,
                               int flowFileStartIndex, int flowFileEndIndex) :
    _width(width),
    _height(height)
{
    ////////////////////////////////
    // TIME-VARYING SERIES
    _isTimeVaryingField = timeVaryingData;
    _flowFileStartIndex = flowFileStartIndex;
    _flowFileEndIndex = flowFileEndIndex;
    _userDefinedParticleMaxCount = width * height;

    _skipByte = 0;

    _screenWidth = _screenHeight = 1;
    _fov = 60.0f;

    _particleMaxCount = _width * _height;

    _pointSize = 10.0f;
    _camx = 0.0f;
    _camy = 0.0f;
    _camz = 0.0f;

    _scalex = _scaley = _scalez = 1.0f;
    _currentSortIndex = 0;
    _destSortIndex = 1;

    _currentPosIndex = 0;
    _destPosIndex = 1;

    _currentSortPass = 0;
    // TBD
    //_sortPassesPerFrame = 5;
    _sortPassesPerFrame = 4;
    _maxSortPasses = 0;

    _sortBegin = 0;
    _sortEnd = _sortPassesPerFrame;
    _currentTime = 0;
    _sortEnabled = false;
    _glyphEnabled = false;
    _advectionEnabled = false;
    _streamlineEnabled = false;
    _particles = new Particle[_particleMaxCount];
    memset(_particles, 0, sizeof(Particle) * _particleMaxCount);

    _colorBuffer = new color4[_particleMaxCount];
    memset(_colorBuffer, 0, sizeof(color4) * _particleMaxCount);

    _positionBuffer = new vrmath::Vector3f[_particleMaxCount];
    _vertices = new RenderVertexArray(_particleMaxCount, 3, GL_FLOAT);

    srand(time(0));

    /*
    // TBD..
    glGenBuffersARB(1, &_colorBufferID);
    glBindBufferARB(GL_ARRAY_BUFFER, _colorBufferID);
    glBufferDataARB(GL_ARRAY_BUFFER, _width * _height * 4, _colorBuffer, GL_STREAM_DRAW_ARB); // undefined data
    glBindBufferARB(GL_ARRAY_BUFFER, 0);
    */

    _flowWidth = fieldWidth;
    _flowHeight = fieldHeight;
    _flowDepth = fieldDepth;

    float min, max, nonzero_min, axisScaleX, axisScaleY, axisScaleZ;
    int index = fileName.rfind('.');
    std::string ext = fileName.substr(index + 1, fileName.size() - (index + 1));
    float *data = 0;

    if (this->isTimeVaryingField()) {
        axisScaleX = _flowWidth;
        axisScaleY = _flowHeight;
        axisScaleZ = _flowDepth;
        _fileNameFormat = fileName;
        for (int i = 0; i < CircularFifo<float*, 10>::Capacity; ++i) {
            _queue.array[i] = new float[_flowWidth * _flowHeight * _flowDepth * 4];
        }

        // INSOO
        // TBD
        min = 0;
        max = 234.99;
    } else {
        if (ext == "dx") {
            data = (float*) LoadFlowDx(fileName.c_str(), _flowWidth, _flowHeight, _flowDepth, min, max, nonzero_min, axisScaleX, axisScaleY, axisScaleZ);
        } else if (ext == "raw") {
            data = (float*) LoadFlowRaw(fileName.c_str(), _flowWidth, _flowHeight, _flowDepth, min, max, nonzero_min, axisScaleX, axisScaleY, axisScaleZ, 0, false);
            //data = (float*) LoadProcessedFlowRaw(fileName.c_str(), _flowWidth, _flowHeight, _flowDepth, min, max, axisScaleX, axisScaleY, axisScaleZ);
#ifdef notdef
        } else if (ext == "raws") {
            data = (float*) LoadFlowRaw(fileName.c_str(), _flowWidth, _flowHeight, _flowDepth, min, max, nonzero_min, axisScaleX, axisScaleY, axisScaleZ, 5 * sizeof(int), true);
        } else if (ext == "data") {
            data = (float*) LoadFlowRaw(fileName.c_str(), _flowWidth, _flowHeight, _flowDepth, min, max, nonzero_min, axisScaleX, axisScaleY, axisScaleZ, 0, true);
#endif
        }
        //_criticalPoints = find_critical_points((vrmath::Vector4f*) data, _flowWidth,  _flowHeight,  _flowDepth);
        //algorithm_test((vrmath::Vector4f*) data,  _flowWidth,  _flowHeight,  _flowDepth);
    }

    _scalex = 1;
    _scaley = axisScaleY / axisScaleX;
    _scalez = axisScaleZ / axisScaleX;
    _maxVelocityScale = max;

    if (!this->isTimeVaryingField()) {
        Texture3D *flow = new Texture3D(_flowWidth, _flowHeight, _flowDepth,
                                        GL_FLOAT, GL_LINEAR, 4, data);
        _curVectorFieldID = flow->id();
        _vectorFieldIDs.push_back(_curVectorFieldID);
    } else {
        for (int i = 0; i < 3; ++i) {
            Texture3D *flow = new Texture3D(_flowWidth, _flowHeight, _flowDepth,
                                            GL_FLOAT, GL_LINEAR, 4, data);
            _vectorFields.push_back(flow);
            _vectorFieldIDs.push_back(flow->id());
        }
        _curVectorFieldID = _vectorFieldIDs[0];
    }

    std::string path = FilePath::getInstance()->getPath("arrows.bmp");

    if (!path.empty()) {
        ImageLoader *loader = ImageLoaderFactory::getInstance()->createLoader("bmp");
        if (loader != NULL) {
#ifdef USE_RGBA_ARROW
            Image *image = loader->load(path.c_str(), Image::IMG_RGBA);
#else
            Image *image = loader->load(path.c_str(), Image::IMG_RGB);
#endif
            if (image != NULL) {
                unsigned char *bytes = (unsigned char *)image->getImageBuffer();
                if (bytes != NULL) {
#ifdef USE_RGBA_ARROW
                    _arrows = new Texture2D(image->getWidth(), image->getHeight(),
                                            GL_UNSIGNED_BYTE, GL_LINEAR, 4, NULL);
#else
                    _arrows = new Texture2D(image->getWidth(), image->getHeight(),
                                            GL_UNSIGNED_BYTE, GL_LINEAR, 3, NULL);
#endif
                    _arrows->setWrapS(GL_MIRRORED_REPEAT);
                    _arrows->setWrapT(GL_MIRRORED_REPEAT);
                    _arrows->initialize(image->getImageBuffer());
                }
                delete image;
            } else {
                ERROR("Failed to load image: arrows.bmp");
            }
            delete loader;
        } else {
            ERROR("Couldn't find loader for arrows.bmp");
        }
    } else {
        ERROR("Couldn't find path to arrows.bmp");
    }

#ifdef TEST
    MakeSphereTexture();
#endif

    glGenBuffersARB(1, &_particleInfoBufferID);
    glBindBufferARB(GL_ARRAY_BUFFER_ARB, _particleInfoBufferID);
    glBufferDataARB(GL_ARRAY_BUFFER_ARB, _particleMaxCount * 4 * sizeof(float), 0, GL_DYNAMIC_DRAW);
    glVertexAttribPointerARB(8, 4, GL_FLOAT, GL_FALSE, 0, 0);  // 8 = texcoord0
    glBindBufferARB(GL_ARRAY_BUFFER_ARB, 0);

    // TBD..
    initStreamlines(_width, _height);
    initInitPosTex();

    initShaders();
    createRenderTargets();
    createSortRenderTargets();
    createStreamlineRenderTargets();

    if (this->isTimeVaryingField()) {
        pthread_t _threads;
        pthread_attr_t pthread_custom_attr;
        pthread_attr_init(&pthread_custom_attr);
        pthread_create(&_threads, &pthread_custom_attr, dataLoadMain, (void *) this);
    }
}

void ParticleSystem::initInitPosTex()
{
    glGenFramebuffersEXT(1, &_initPos_fbo);
    glGenTextures(1, &_initPosTex);

    glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, _initPos_fbo);

    glViewport(0, 0, _width, _height);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    glOrtho(0, _width, 0, _height, -10.0f, 10.0f);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();

    glBindTexture(GL_TEXTURE_RECTANGLE_ARB, _initPosTex);
    glTexParameterf(GL_TEXTURE_RECTANGLE_ARB, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
    glTexParameterf(GL_TEXTURE_RECTANGLE_ARB, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
    glTexParameteri(GL_TEXTURE_RECTANGLE_ARB, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
    glTexParameteri(GL_TEXTURE_RECTANGLE_ARB, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
    glTexImage2D(GL_TEXTURE_RECTANGLE_ARB, 0, GL_RGB32F_ARB,
                 _width, _height, 0, GL_RGB, GL_FLOAT, NULL);
    glBindTexture(GL_TEXTURE_RECTANGLE_ARB, 0);

    glFramebufferTexture2DEXT(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT, 
                              GL_TEXTURE_RECTANGLE_ARB, _initPosTex, 0);

    glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);
}

void ParticleSystem::initStreamlines(int width, int height)
{
    _atlas_x = 32;
    _atlas_y = 32;

    _atlasWidth = width * _atlas_x;
    _atlasHeight = height * _atlas_y;
    _maxAtlasCount = _atlas_x * _atlas_y;

    _stepSizeStreamline = 1;
    _curStepCount = 0;
    _particleCount = width * height;

    _currentStreamlineOffset = 0;
    _currentStreamlineIndex = 0;
    _streamVertices = new RenderVertexArray(_atlasWidth*_atlasHeight * 2, 3, GL_FLOAT);

    _maxIndexBufferSize = _width * _height * _atlas_x * _atlas_y;
    _indexBuffer = new unsigned int[_maxIndexBufferSize * 2];
    unsigned int* pindex = _indexBuffer;
    int ax, ay, old_ax = 0, old_ay = 0;
    for (unsigned int i = 1; i < _maxAtlasCount; ++i) {
        ax = (i % _atlas_x) * width;
        ay = (i / _atlas_x) * height;

        for (int y = 0; y < height ; ++y) {
            for (int x = 0; x < width; ++x) {
                *pindex = (old_ay + y) * _atlasWidth + old_ax + x; ++pindex;
                *pindex = (ay + y) * _atlasWidth + ax + x; ++pindex;
            }
        }

        old_ax = ax;
        old_ay = ay;
    }
}

void ParticleSystem::initShaders()
{
    // TBD...
    _context = Shader::getCgContext();

    std::string path = FilePath::getInstance()->getPath("distance.cg");
    _distanceInitFP =  
        cgCreateProgramFromFile(_context, CG_SOURCE, path.c_str(),
                                CG_PROFILE_FP40, "initSortIndex", NULL);
    cgGLLoadProgram(_distanceInitFP);

    _distanceSortFP = 
        cgCreateProgramFromFile(_context, CG_SOURCE,  path.c_str(),
                                CG_PROFILE_FP40, "computeDistance", NULL);
    _viewPosParam = cgGetNamedParameter(_distanceSortFP, "viewerPosition");
    cgGLLoadProgram(_distanceSortFP);

    _distanceSortLookupFP = 
        cgCreateProgramFromFile(_context, CG_SOURCE,  path.c_str(),
                                CG_PROFILE_FP40, "lookupPosition", NULL);
    cgGLLoadProgram(_distanceSortLookupFP);

    path = FilePath::getInstance()->getPath("mergesort.cg");
    _sortRecursionFP = 
        cgCreateProgramFromFile(_context, CG_SOURCE, path.c_str(),
                                CG_PROFILE_FP40, "mergeSortRecursion", NULL);
    cgGLLoadProgram(_sortRecursionFP);

    _srSizeParam = cgGetNamedParameter(_sortRecursionFP, "_Size");
    _srStepParam = cgGetNamedParameter(_sortRecursionFP, "_Step");
    _srCountParam = cgGetNamedParameter(_sortRecursionFP, "_Count");

    _sortEndFP = 
        cgCreateProgramFromFile(_context, CG_SOURCE, path.c_str(),
                                CG_PROFILE_FP40, "mergeSortEnd", NULL);
    cgGLLoadProgram(_sortEndFP);

    _seSizeParam = cgGetNamedParameter(_sortEndFP, "size");
    _seStepParam = cgGetNamedParameter(_sortEndFP, "step");

    path = FilePath::getInstance()->getPath("passthrough.cg");
    _passthroughFP = 
        cgCreateProgramFromFile(_context, CG_SOURCE, path.c_str(),
                                CG_PROFILE_FP40, "main", NULL);
    cgGLLoadProgram(_passthroughFP);

    _scaleParam = cgGetNamedParameter(_passthroughFP, "scale");
    _biasParam = cgGetNamedParameter(_passthroughFP, "bias");

    path = FilePath::getInstance()->getPath("moveparticles.cg");
    _moveParticlesFP = 
        cgCreateProgramFromFile(_context, CG_SOURCE, path.c_str(),
                                CG_PROFILE_FP40, "main", NULL);
    cgGLLoadProgram(_moveParticlesFP);
    _mpTimeScale = cgGetNamedParameter(_moveParticlesFP, "timeStep");
    _mpVectorField = cgGetNamedParameter(_moveParticlesFP, "vfield");
    _mpUseInitTex= cgGetNamedParameter(_moveParticlesFP, "useInitPos");
    _mpCurrentTime= cgGetNamedParameter(_moveParticlesFP, "currentTime");
    _mpMaxScale = cgGetNamedParameter(_moveParticlesFP, "maxScale");
    _mpScale= cgGetNamedParameter(_moveParticlesFP, "scale");

    path = FilePath::getInstance()->getPath("particlevp.cg");
    _particleVP = 
        cgCreateProgramFromFile(_context, CG_SOURCE, path.c_str(),
                                CG_PROFILE_VP40, "vpmain", NULL);
    cgGLLoadProgram(_particleVP);
    _mvpParticleParam = cgGetNamedParameter(_particleVP, "mvp");
    _mvParticleParam = cgGetNamedParameter(_particleVP, "modelview");
    _mvTanHalfFOVParam = cgGetNamedParameter(_particleVP, "tanHalfFOV");
    _mvCurrentTimeParam =  cgGetNamedParameter(_particleVP, "currentTime");

    path = FilePath::getInstance()->getPath("particlefp.cg");
    _particleFP = 
        cgCreateProgramFromFile(_context, CG_SOURCE, path.c_str(),
                                CG_PROFILE_FP40, "fpmain", NULL);
    cgGLLoadProgram(_particleFP);
    _vectorParticleParam = cgGetNamedParameter(_particleVP, "vfield");

    path = FilePath::getInstance()->getPath("moveparticles.cg");
    _initParticlePosFP = 
        cgCreateProgramFromFile(_context, CG_SOURCE, path.c_str(),
				CG_PROFILE_FP40, "initParticlePosMain", NULL);
    cgGLLoadProgram(_initParticlePosFP);
    _ipVectorFieldParam = cgGetNamedParameter(_moveParticlesFP, "vfield");
}

void ParticleSystem::passThoughPositions()
{
    cgGLBindProgram(_passthroughFP);
    cgGLEnableProfile(CG_PROFILE_FP40);

    cgGLSetParameter4f(_scaleParam, 1.0, 1.0, 1.0, 1.0);
    cgGLSetParameter4f(_biasParam, 0.0, 0.0, 0.0, 0.0);

    glTexImage2D(GL_TEXTURE_RECTANGLE_ARB, 0, GL_RGB32F_ARB, 
                 _width, _height, 0, GL_RGB, GL_FLOAT, (GLfloat *) _positionBuffer);

    drawQuad();

    cgGLDisableProfile(CG_PROFILE_FP40);
}

void ParticleSystem::resetStreamlines()
{
    _currentStreamlineIndex = 0;
    _currentStreamlineOffset = 0;
    _curStepCount = 0;
}

void ParticleSystem::reset()
{
    _currentTime = 0.0f;
    _sortBegin = 0;
    _sortEnd = _sortPassesPerFrame;

    glPushAttrib(GL_VIEWPORT_BIT);
    glMatrixMode(GL_PROJECTION);
    glPushMatrix();
    glMatrixMode(GL_MODELVIEW);

    resetStreamlines();

    unsigned int maxsize = _userDefinedParticleMaxCount;

    while (!_availableIndices.empty())
        _availableIndices.pop();
    while (!_activeParticles.empty())
        _activeParticles.pop();

    _activeParticles.reserve(maxsize);
    _availableIndices.reserve(maxsize);

    for (unsigned int i = 0; i < maxsize; i++)
        _availableIndices.push(i);

    for (int i = 0; i < _particleMaxCount; i++) {
        _particles[i].timeOfBirth = -1.0f;
        _particles[i].lifeTime = 0.0f;
        _particles[i].attributeType = 0.0f;
        _particles[i].index = (float)i;
    }

    glBindBufferARB(GL_ARRAY_BUFFER_ARB, _particleInfoBufferID);
    Particle* pinfo = (Particle*) glMapBufferARB(GL_ARRAY_BUFFER, GL_WRITE_ONLY_ARB);

    for (int i = 0; i < _particleMaxCount; i++)	{
        pinfo[i] = _particles[i];
    }

    glUnmapBufferARB(GL_ARRAY_BUFFER_ARB);

    // POSITION
    memset(_positionBuffer, 0, sizeof(vrmath::Vector3f) * _width * _height);
    for (int y = 0; y < _height; y++) {
        for (int x = 0; x < _width; x++) {
            _positionBuffer[_width * y + x].x = (float)rand() / (float) RAND_MAX;
            //_positionBuffer[_width * y + x].x = 0.9;
            _positionBuffer[_width * y + x].y = (float)rand() / (float) RAND_MAX;
            _positionBuffer[_width * y + x].z = (float)rand() / (float) RAND_MAX;
        }
    }

    glBindTexture(GL_TEXTURE_RECTANGLE_ARB, _initPosTex);
    glTexImage2D(GL_TEXTURE_RECTANGLE_ARB, 0, GL_RGB32F_ARB,
                 _width, _height, 0, GL_RGB, GL_FLOAT, (float*)_positionBuffer);
    glBindTexture(GL_TEXTURE_RECTANGLE_ARB, 0);

    glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, psys_fbo[_currentPosIndex]);
    glViewport(0, 0, _width, _height);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    glOrtho(0, _width, 0, _height, -10.0f, 10.0f);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    passThoughPositions();
    glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);

    glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, velocity_fbo[_currentPosIndex]);
    glViewport(0, 0, _width, _height);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    glOrtho(0, _width, 0, _height, -10.0f, 10.0f);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
    glClearColor(0, 0, 0, 0);
    glClear(GL_COLOR_BUFFER_BIT);
    // TBD..
    // velocity
    glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);


    /// TBD...
    //DeathTimePBuffer->BeginCapture();
    //glClear(GL_COLOR_BUFFER_BIT);
    //DeathTimePBuffer->EndCapture();

    if (_sortEnabled) {
        glDisable(GL_BLEND);
        glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, sort_fbo[_currentSortIndex]);
        glViewport(0, 0, _width, _height);
        glMatrixMode(GL_PROJECTION);
        glLoadIdentity();
        glOrtho(0, _width, 0, _height, -10.0f, 10.0f);
        glMatrixMode(GL_MODELVIEW);
        glLoadIdentity();

        cgGLBindProgram(_distanceInitFP);
        cgGLEnableProfile(CG_PROFILE_FP40);

        drawQuad();

        cgGLDisableProfile(CG_PROFILE_FP40);
        glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);		

        _currentSortPass = 0;
        this->_maxSortPasses = 100000;
    }

    glMatrixMode(GL_PROJECTION);
    glPopMatrix();
    glMatrixMode(GL_MODELVIEW);
    glPopAttrib();
}

void ParticleSystem::createRenderTargets()
{
    glGenFramebuffersEXT(2, psys_fbo);
    glGenTextures(2, psys_tex);

    glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, psys_fbo[0]);

    glViewport(0, 0, _width, _height);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    glOrtho(0, _width, 0, _height, -10.0f, 10.0f);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();

    glBindTexture(GL_TEXTURE_RECTANGLE_ARB, psys_tex[0]);
    glTexParameterf(GL_TEXTURE_RECTANGLE_ARB, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
    glTexParameterf(GL_TEXTURE_RECTANGLE_ARB, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
    glTexParameteri(GL_TEXTURE_RECTANGLE_ARB, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
    glTexParameteri(GL_TEXTURE_RECTANGLE_ARB, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);

    glTexImage2D(GL_TEXTURE_RECTANGLE_ARB, 0, GL_RGBA32F_ARB, 
                 _width, _height, 0, GL_RGBA, GL_FLOAT, NULL);

    glFramebufferTexture2DEXT(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT, 
                              GL_TEXTURE_RECTANGLE_ARB, psys_tex[0], 0);

    glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, psys_fbo[1]);

    glBindTexture(GL_TEXTURE_RECTANGLE_ARB, psys_tex[1]);
    glViewport(0, 0, _width, _height);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    glOrtho(0, _width, 0, _height, -10.0f, 10.0f);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();

    glTexParameterf(GL_TEXTURE_RECTANGLE_ARB, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
    glTexParameterf(GL_TEXTURE_RECTANGLE_ARB, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
    glTexParameteri(GL_TEXTURE_RECTANGLE_ARB, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
    glTexParameteri(GL_TEXTURE_RECTANGLE_ARB, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);

    glTexImage2D(GL_TEXTURE_RECTANGLE_ARB, 0, GL_RGBA32F_ARB, 
                 _width, _height, 0, GL_RGBA, GL_FLOAT, NULL);

    glFramebufferTexture2DEXT(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT, 
                              GL_TEXTURE_RECTANGLE_ARB, psys_tex[1], 0);
 
    glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);
}

//#define ATLAS_TEXTURE_TARGET GL_TEXTURE_RECTANGLE_ARB
//#define ATLAS_INTERNAL_TYPE GL_RGBA32F_ARB
#define ATLAS_TEXTURE_TARGET GL_TEXTURE_2D
#define ATLAS_INTERNAL_TYPE GL_RGBA

void ParticleSystem::createStreamlineRenderTargets()
{
    glGenFramebuffersEXT(1, &_atlas_fbo);
    glGenTextures(1, &_atlas_tex);
    glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, _atlas_fbo);
    glViewport(0, 0, _atlasWidth, _atlasHeight);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    glOrtho(0, _atlasWidth, 0, _atlasHeight, -10.0f, 10.0f);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();

    glBindTexture(ATLAS_TEXTURE_TARGET, _atlas_tex);
    glTexParameterf(ATLAS_TEXTURE_TARGET, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
    glTexParameterf(ATLAS_TEXTURE_TARGET, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
    //glTexParameteri(ATLAS_TEXTURE_TARGET, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
    //glTexParameteri(ATLAS_TEXTURE_TARGET, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);

    glTexImage2D(ATLAS_TEXTURE_TARGET, 0, ATLAS_INTERNAL_TYPE, 
                 _atlasWidth, _atlasHeight, 0, GL_RGBA, GL_FLOAT, NULL);

    glFramebufferTexture2DEXT(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT, 
                              ATLAS_TEXTURE_TARGET, _atlas_tex, 0);
 
    glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);
}

//#define SORT_TEXTURE_FORMAT  GL_LUMINANCE_ALPHA
//#define SORT_TEXTURE_INNER_FORMAT GL_LUMINANCE_ALPHA_FLOAT32_ATI
#define SORT_TEXTURE_FORMAT  GL_RGB
#define SORT_TEXTURE_INNER_FORMAT GL_RGB32F_ARB

void ParticleSystem::createSortRenderTargets()
{
    glGenFramebuffersEXT(2, sort_fbo);
    glGenTextures(2, sort_tex);

    glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, sort_fbo[0]);
    glViewport(0, 0, _width, _height);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    glOrtho(0, _width, 0, _height, -10.0f, 10.0f);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();

    glBindTexture(GL_TEXTURE_RECTANGLE_ARB, sort_tex[0]);
    glTexParameterf(GL_TEXTURE_RECTANGLE_ARB, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
    glTexParameterf(GL_TEXTURE_RECTANGLE_ARB, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
    glTexParameteri(GL_TEXTURE_RECTANGLE_ARB, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
    glTexParameteri(GL_TEXTURE_RECTANGLE_ARB, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
    glTexImage2D(GL_TEXTURE_RECTANGLE_ARB, 0, SORT_TEXTURE_INNER_FORMAT, 
                 _width, _height, 0, SORT_TEXTURE_FORMAT, GL_FLOAT, NULL);

    glFramebufferTexture2DEXT(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT, 
                              GL_TEXTURE_RECTANGLE_ARB, sort_tex[0], 0);

    glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, sort_fbo[1]);
    glViewport(0, 0, _width, _height);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    glOrtho(0, _width, 0, _height, -10.0f, 10.0f);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();

    glBindTexture(GL_TEXTURE_RECTANGLE_ARB, sort_tex[1]);
    glTexParameterf(GL_TEXTURE_RECTANGLE_ARB, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
    glTexParameterf(GL_TEXTURE_RECTANGLE_ARB, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
    glTexParameteri(GL_TEXTURE_RECTANGLE_ARB, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
    glTexParameteri(GL_TEXTURE_RECTANGLE_ARB, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
    glTexImage2D(GL_TEXTURE_RECTANGLE_ARB, 0, SORT_TEXTURE_INNER_FORMAT, 
                 _width, _height, 0, SORT_TEXTURE_FORMAT, GL_FLOAT, NULL);

    glFramebufferTexture2DEXT(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT, 
                              GL_TEXTURE_RECTANGLE_ARB, sort_tex[1], 0);

    glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);
}

ParticleSystem::~ParticleSystem()
{
    std::vector<ParticleEmitter*>::iterator iter;
    for (iter = _emitters.begin(); iter != _emitters.end(); ++iter)
        delete (*iter);

    // Particle Position
    glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, psys_fbo[0]);
    glDeleteTextures(1, psys_tex);
    glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, psys_fbo[1]);
    glDeleteTextures(1, psys_tex+1);
    glDeleteFramebuffersEXT(2, psys_fbo);

    // Sort
    glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, sort_fbo[0]);
    glDeleteTextures(1, sort_tex);
    glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, sort_fbo[1]);
    glDeleteTextures(1, sort_tex+1);
    glDeleteFramebuffersEXT(2, sort_fbo);

    glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, velocity_fbo[0]);
    glDeleteTextures(1, velocity_tex);
    glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, velocity_fbo[1]);
    glDeleteTextures(1, velocity_tex+1);
    glDeleteFramebuffersEXT(2, velocity_fbo);

    if (_vertices) delete _vertices;

    delete [] _particles;
    delete [] _positionBuffer;
    delete [] _colorBuffer;

    if (_arrows) delete _arrows;

    // STREAM LINE
    if (_streamVertices) delete _streamVertices;
    if (_indexBuffer) delete _indexBuffer;

    cgDestroyProgram(_distanceInitFP);

    cgDestroyParameter(_viewPosParam);
    cgDestroyProgram(_distanceSortFP);

    cgDestroyProgram(_distanceSortLookupFP);

    cgDestroyParameter(_scaleParam);
    cgDestroyParameter(_biasParam);
    cgDestroyProgram(_passthroughFP);

    cgDestroyParameter(_srSizeParam);
    cgDestroyParameter(_srStepParam);
    cgDestroyParameter(_srCountParam);

    cgDestroyProgram(_sortRecursionFP);

    cgDestroyParameter(_seSizeParam);
    cgDestroyParameter(_seStepParam);
    cgDestroyProgram(_sortEndFP);

    cgDestroyParameter(_mpTimeScale);
    cgDestroyParameter(_mpVectorField);
    cgDestroyParameter(_mpUseInitTex);
    cgDestroyParameter(_mpCurrentTime);
    cgDestroyProgram(_moveParticlesFP);

    cgDestroyParameter(_ipVectorFieldParam);
    cgDestroyProgram(_initParticlePosFP);

    cgDestroyParameter(_mvpParticleParam);
    cgDestroyParameter(_mvParticleParam);
    cgDestroyParameter(_mvTanHalfFOVParam);
    cgDestroyParameter(_mvCurrentTimeParam);
    cgDestroyProgram(_particleFP);

    cgDestroyParameter(_vectorParticleParam);
    cgDestroyProgram(_particleVP);
}

bool ParticleSystem::isEnabled(EnableEnum enabled)
{
    switch (enabled) {
    case PS_SORT :
        return _sortEnabled;
        break;
    case PS_GLYPH :
        return _glyphEnabled;
        break;
    case PS_DRAW_BBOX :
        return _drawBBoxEnabled;
        break;
    case PS_ADVECTION :
        return _advectionEnabled;
    case PS_STREAMLINE :
        return _streamlineEnabled;
    }
    return false;
}

void ParticleSystem::enable(EnableEnum enabled)
{
    switch (enabled) {
    case PS_SORT :
        _sortEnabled = true;
        break;
    case PS_GLYPH :
        _glyphEnabled = true;
        break;
    case PS_DRAW_BBOX :
        _drawBBoxEnabled = true;
        break;
    case PS_ADVECTION :
        _advectionEnabled = true;
        break;
    case PS_STREAMLINE :
        _streamlineEnabled = true;
        break;
    }
}

void ParticleSystem::disable(EnableEnum enabled)
{
    switch (enabled) {
    case PS_SORT :
        _sortEnabled = false;
        break;
    case PS_GLYPH :
        _glyphEnabled = false;
        break;
    case PS_DRAW_BBOX :
        _drawBBoxEnabled = false;
        break;
    case PS_ADVECTION :
        _advectionEnabled = false;
        break;
    case PS_STREAMLINE :
        _streamlineEnabled = false;
        break;
    }
}

void ParticleSystem::advectStreamlines()
{
    glDisable(GL_BLEND);
    glDisable(GL_DEPTH_TEST);

    //glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, psys_fbo[_destPosIndex]);
    //glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    glPushAttrib(GL_VIEWPORT_BIT);
    glViewport(0, 0, _width, _height);
    glMatrixMode(GL_PROJECTION);
    glPushMatrix();
    glLoadIdentity();
    glOrtho(0, _width, 0, _height, -10.0f, 10.0f);
    glMatrixMode(GL_MODELVIEW);
    glPushMatrix();
    glLoadIdentity();

    glEnable(GL_TEXTURE_RECTANGLE_ARB);

    cgGLBindProgram(_moveParticlesFP);
    cgGLEnableProfile(CG_PROFILE_FP40);
    cgGLSetParameter1f(_mpTimeScale, 0.005);
    cgGLSetParameter1f(_mpUseInitTex, 1.0);
    cgGLSetParameter1f(_mpCurrentTime, _currentTime);
    cgGLSetParameter3f(_mpScale, _scalex, _scaley, _scalez);
    cgGLSetParameter1f(_mpMaxScale, _maxVelocityScale);
    cgGLSetTextureParameter(_mpVectorField, _curVectorFieldID);
    cgGLEnableTextureParameter(_mpVectorField);

    for (int i = 0; i < _stepSizeStreamline; ++i) {
        glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, psys_fbo[_destPosIndex]);
        glClear(GL_COLOR_BUFFER_BIT);
        glActiveTextureARB(GL_TEXTURE0_ARB);
        glBindTexture(GL_TEXTURE_RECTANGLE_ARB, psys_tex[_currentPosIndex]);
        glActiveTextureARB(GL_TEXTURE1_ARB);
        glBindTexture(GL_TEXTURE_RECTANGLE_ARB, _initPosTex);
        drawQuad();
        swap(_currentPosIndex, _destPosIndex);
    }

    cgGLDisableTextureParameter(_mpVectorField);
    glDisable(GL_TEXTURE_RECTANGLE_ARB);
    cgGLDisableProfile(CG_PROFILE_FP40);

    glMatrixMode(GL_PROJECTION);
    glPopMatrix();
    glMatrixMode(GL_MODELVIEW);
    glPopMatrix();
    glPopAttrib();
    glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);

    if (_currentStreamlineIndex < _maxAtlasCount) {
        int xoffset = (_currentStreamlineIndex % _atlas_x) * _width;
        int yoffset = (_currentStreamlineIndex / _atlas_x) * _height;

        glActiveTextureARB(GL_TEXTURE0_ARB);
        glEnable(ATLAS_TEXTURE_TARGET);
        glBindTexture(ATLAS_TEXTURE_TARGET, _atlas_tex);

        glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, psys_fbo[_destPosIndex]);
        //glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, psys_fbo[_currentPosIndex]);
        glCopyTexSubImage2D(ATLAS_TEXTURE_TARGET, 0, xoffset, yoffset, 
                            0, 0, _width, _height);
        glActiveTextureARB(GL_TEXTURE0_ARB);
        glBindTexture(ATLAS_TEXTURE_TARGET, 0);
        glDisable(ATLAS_TEXTURE_TARGET);

        glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, _atlas_fbo);
        _streamVertices->read(_atlasWidth, _atlasHeight);
        glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);
        _currentStreamlineIndex++;

        glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);
    }
}

bool ParticleSystem::advect(float deltaT, float camx, float camy, float camz)
{
    static bool firstLoad = true;
    if (this->isTimeVaryingField()) {
        static float oldTime = (float)clock()/(float)CLOCKS_PER_SEC;
#ifdef WANT_TRACE
        static int index = 0;
#endif
        float time = (float)clock()/(float)CLOCKS_PER_SEC;
        if ((time - oldTime) > 2.0) {
            if (!_queue.isEmpty()) {
                float *data = NULL;
                if (_queue.top(data)) {
#ifdef WANT_TRACE
                    float t = clock() /(float) CLOCKS_PER_SEC;
#endif
                    _vectorFields[0]->update(data);
#ifdef WANT_TRACE
                    float ti = clock() / (float) CLOCKS_PER_SEC;
                    TRACE("updatePixels time: %f", ti - t);
#endif
                    _queue.pop();
                    oldTime = time;

                    firstLoad = false;
                    TRACE("%d bound", index++);
                }
            }		
        }
        if (firstLoad) return false;
    }

    if (!_advectionEnabled) return true;
    if (this->_streamlineEnabled) {
        advectStreamlines();
        _currentTime += deltaT;
    } else {
        _camx = camx;
        _camy = camy;
        _camz = camz;

        glDisable(GL_BLEND);
        glDisable(GL_DEPTH_TEST);

        glPushAttrib(GL_VIEWPORT_BIT);
        glViewport(0, 0, _width, _height);
        glMatrixMode(GL_PROJECTION);
        glPushMatrix();
        glLoadIdentity();
        glOrtho(0, _width, 0, _height, -10.0f, 10.0f);
        glMatrixMode(GL_MODELVIEW);
        glPushMatrix();
        glLoadIdentity();

        glEnable(GL_TEXTURE_RECTANGLE_ARB);

        cgGLBindProgram(_moveParticlesFP);
        cgGLEnableProfile(CG_PROFILE_FP40);

        // INSOO
        // TIME SCALE

        cgGLSetParameter1f(_mpTimeScale, 0.005);

        //////////////////////////////////////////////////////
        // UPDATE POS
        cgGLSetTextureParameter(_mpVectorField, _curVectorFieldID);
        cgGLEnableTextureParameter(_mpVectorField);
        cgGLSetParameter3f(_mpScale, _scalex, _scaley, _scalez);
        cgGLSetParameter1f(_mpMaxScale, _maxVelocityScale);
        for (int i = 0; i < _stepSizeStreamline; ++i) {
            glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, psys_fbo[_destPosIndex]);
            glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
            glActiveTextureARB(GL_TEXTURE0_ARB);
            glBindTexture(GL_TEXTURE_RECTANGLE_ARB, psys_tex[_currentPosIndex]);
            glActiveTextureARB(GL_TEXTURE1_ARB);
            glBindTexture(GL_TEXTURE_RECTANGLE_ARB, _initPosTex);
            drawQuad();
            swap(_currentPosIndex, _destPosIndex);
        }
        cgGLDisableTextureParameter(_mpVectorField);

        glActiveTextureARB(GL_TEXTURE1_ARB);
        glDisable(GL_TEXTURE_RECTANGLE_ARB);
        glActiveTextureARB(GL_TEXTURE0_ARB);
        glDisable(GL_TEXTURE_RECTANGLE_ARB);

        glDisable(GL_TEXTURE_RECTANGLE_ARB);
        cgGLDisableProfile(CG_PROFILE_FP40);

        glMatrixMode(GL_PROJECTION);
        glPopMatrix();
        glMatrixMode(GL_MODELVIEW);
        glPopMatrix();
        glPopAttrib();
        glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);

        if (_sortEnabled) {
            sort();

            glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, psys_fbo[_destPosIndex]);
            _vertices->read(_width, _height);
            glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);
        } else {
            glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, psys_fbo[_currentPosIndex]);
            _vertices->read(_width, _height);
            glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);
        }

        // NEW PARTICLES
        for (unsigned int i = 0; i < _emitters.size(); ++i) {
            // TBD..
            unsigned int numOfNewParticles = (unsigned int)(randomRange(_emitters[i]->_minNumOfNewParticles, _emitters[i]->_maxNumOfNewParticles) * deltaT);
            for (unsigned int k = 0; k < numOfNewParticles; ++k) {
                vrmath::Vector3f position = _emitters[i]->_position;
                position +=
                    _emitters[i]->_maxPositionOffset.scale(vrmath::Vector3f(randomRange(-1.0f, 1.0f),
                                                                            randomRange(-1.0f, 1.0f),
                                                                            randomRange(-1.0f, 1.0f)));
                float lifetime = randomRange(_emitters[i]->_minLifeTime, _emitters[i]->_maxLifeTime);

                // TBD..
                allocateParticle(position, vrmath::Vector3f(0.0f, 0.0f, 0.0f),  lifetime, 1 - (float) k / numOfNewParticles);
            }
        }

        initNewParticles();

        _currentTime += deltaT;

        cleanUpParticles();
    }

    return true;
}

void ParticleSystem::allocateParticle(const vrmath::Vector3f& position, const vrmath::Vector3f& velocity,
                                      float lifeTime, float initTimeStep)
{
    if (_availableIndices.empty()) {
        return;
    }

    int index = _availableIndices.top(); 
    _availableIndices.pop();

    ActiveParticle p;
    p.index = index;
    p.timeOfDeath = _currentTime + lifeTime;
    _activeParticles.push(p);

    NewParticle newParticle;
    newParticle.index = index;
    newParticle.position = position;
    newParticle.velocity = velocity;
    newParticle.timeOfDeath = p.timeOfDeath;
    newParticle.initTimeStep = initTimeStep;

    _newParticles.push_back(newParticle);

    _particles[index].timeOfBirth = _currentTime;
    _particles[index].lifeTime = lifeTime;
}

void ParticleSystem::initNewParticles()
{
    /////////////////////////////
    // INIT NEW PARTICLE
    glBindBufferARB(GL_ARRAY_BUFFER_ARB, _particleInfoBufferID);
    Particle* pinfo = (Particle*) glMapBufferARB(GL_ARRAY_BUFFER, GL_WRITE_ONLY_ARB);

    std::vector<NewParticle>::iterator iter;
    for (iter = _newParticles.begin(); iter != _newParticles.end(); ++iter) {
        pinfo[iter->index] = _particles[iter->index];
    }

    glUnmapBufferARB(GL_ARRAY_BUFFER_ARB);

    glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, psys_fbo[_currentPosIndex]);

    glPushAttrib(GL_VIEWPORT_BIT);
    glViewport(0, 0, _width, _height);
    glMatrixMode(GL_PROJECTION);
    glPushMatrix();
    glLoadIdentity();
    glOrtho(0, _width, 0, _height, -10.0f, 10.0f);
    glMatrixMode(GL_MODELVIEW);
    glPushMatrix();
    glLoadIdentity();

    cgGLBindProgram(_initParticlePosFP);
    cgGLEnableProfile(CG_PROFILE_FP40);
    cgGLSetTextureParameter(_ipVectorFieldParam, _curVectorFieldID);
    cgGLEnableTextureParameter(_ipVectorFieldParam);
    // TBD..
    //glActiveTextureARB(GL_TEXTURE0_ARB);
    //VelocityPBuffers[VelocityCurrent]->Bind();

    glActiveTextureARB(GL_TEXTURE0_ARB);
    glEnable(GL_TEXTURE_RECTANGLE_ARB);
    glBindTexture(GL_TEXTURE_RECTANGLE_ARB, psys_tex[_destPosIndex]);

    glBegin(GL_POINTS);
    for (iter = _newParticles.begin(); iter != _newParticles.end(); iter++) {
        //TRACE("[%d] %f %f %f", iter->index, iter->position.x,iter->position.y,iter->position.z);
        glMultiTexCoord3f(GL_TEXTURE0, iter->position.x,iter->position.y,iter->position.z);

        // TBD..
        //glMultiTexCoord2f(GL_TEXTURE1_ARB, (float)(i->Index % Width), (float)(i->Index / Height));
        //glMultiTexCoord1f(GL_TEXTURE2_ARB, iter->initTimeStep);

        glVertex2f((float)(iter->index % _width),
                   (float)(iter->index / _height) + 1/* + offsetY*/ /* + offsetY shouldn't be */);
        //TRACE("%f %f", (float) (iter->index % _width), (float)(iter->index / _width));
    }
    glEnd();

    glDisable(GL_TEXTURE_RECTANGLE_ARB);
    cgGLDisableTextureParameter(_ipVectorFieldParam);
    cgGLDisableProfile(CG_PROFILE_FP40);

    glMatrixMode(GL_PROJECTION);
    glPopMatrix();
    glMatrixMode(GL_MODELVIEW);
    glPopMatrix();
    glPopAttrib();

    glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);

    // INIT NEW END
    /////////////////////////////
#if 1
    glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, _initPos_fbo);
    glPushAttrib(GL_VIEWPORT_BIT);
    glViewport(0, 0, _width, _height);
    glMatrixMode(GL_PROJECTION);
    glPushMatrix();
    glLoadIdentity();
    glOrtho(0, _width, 0, _height, -10.0f, 10.0f);
    glMatrixMode(GL_MODELVIEW);
    glPushMatrix();
    glLoadIdentity();

    cgGLBindProgram(_initParticlePosFP);
    cgGLEnableProfile(CG_PROFILE_FP40);
    cgGLSetTextureParameter(_ipVectorFieldParam, _curVectorFieldID);
    cgGLEnableTextureParameter(_ipVectorFieldParam);
    // TBD..
    //glActiveTextureARB(GL_TEXTURE0_ARB);
    //VelocityPBuffers[VelocityCurrent]->Bind();

    glActiveTextureARB(GL_TEXTURE0_ARB);
    glEnable(GL_TEXTURE_RECTANGLE_ARB);
    //glBindTexture(GL_TEXTURE_RECTANGLE_ARB, _initPosTex);
    glBindTexture(GL_TEXTURE_RECTANGLE_ARB, psys_tex[_destPosIndex]);

    glBegin(GL_POINTS);
    for (iter = _newParticles.begin(); iter != _newParticles.end(); iter++) {
        //TRACE("[%d] %f %f %f", iter->index, iter->position.x,iter->position.y,iter->position.z);
        glMultiTexCoord3f(GL_TEXTURE0, iter->position.x,iter->position.y,iter->position.z);

        // TBD..
        //glMultiTexCoord2f(GL_TEXTURE1_ARB, (float)(i->Index % Width), (float)(i->Index / Height));
        //glMultiTexCoord1f(GL_TEXTURE2_ARB, iter->initTimeStep);

        glVertex2f((float)(iter->index % _width),
                   (float)(iter->index / _height) + 1/* + offsetY*/ /* + offsetY shouldn't be */);
        //TRACE("%f %f", (float) (iter->index % _width), (float)(iter->index / _width));
    }
    glEnd();

    glDisable(GL_TEXTURE_RECTANGLE_ARB);
    cgGLDisableTextureParameter(_ipVectorFieldParam);
    cgGLDisableProfile(CG_PROFILE_FP40);

    glMatrixMode(GL_PROJECTION);
    glPopMatrix();
    glMatrixMode(GL_MODELVIEW);
    glPopMatrix();
    glPopAttrib();

    glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);
#endif

    // Free array.
    _newParticles.clear();
}

void ParticleSystem::cleanUpParticles()
{
    if (! _activeParticles.empty()) {
        while (_activeParticles.top().timeOfDeath < _currentTime) {
            unsigned int i = _activeParticles.top().index;
            _activeParticles.pop();
            _availableIndices.push(i);
            //_usedIndices[i] = false;

            //if (i >= _maxUsedIndex)
            //    while (!_usedIndices[_maxUsedIndex])
            //        _maxUsedIndex--;
        }
    }
}

void ParticleSystem::sort()
{
    ///////////////////////////////////////////////////////////
    // BEGIN - COMPUTE DISTANCE	
    vrmath::Vector3f pos;
    vrmath::Matrix4x4d mat;
    glPushMatrix();
    glLoadIdentity();
    glScalef(_scalex, _scaley, _scalez);
    glTranslatef(-0.5f, -0.5f, -0.5f);
    glGetDoublev(GL_MODELVIEW_MATRIX, mat.get());
    glPopMatrix();
    mat.invert();
    mat.getTranslation(pos);

    cgGLBindProgram(_distanceSortFP);
    cgGLEnableProfile(CG_PROFILE_FP40);

    glActiveTextureARB(GL_TEXTURE0_ARB);
    glEnable(GL_TEXTURE_RECTANGLE_ARB);
    glBindTexture(GL_TEXTURE_RECTANGLE_ARB, sort_tex[_currentSortIndex]);

    glActiveTextureARB(GL_TEXTURE1_ARB);
    glEnable(GL_TEXTURE_RECTANGLE_ARB);
    glBindTexture(GL_TEXTURE_RECTANGLE_ARB, psys_tex[_currentPosIndex]);

    cgGLSetParameter3f(_viewPosParam, pos.x, pos.y, pos.z);

    glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, sort_fbo[_destSortIndex]);
    glPushAttrib(GL_VIEWPORT_BIT);
    glViewport(0, 0, _width, _height);
    glMatrixMode(GL_PROJECTION);
    glPushMatrix();
    glLoadIdentity();
    glOrtho(0, _width, 0, _height, -10.0f, 10.0f);
    glMatrixMode(GL_MODELVIEW);
    glPushMatrix();
    glLoadIdentity();

    drawQuad();

    cgGLDisableProfile(CG_PROFILE_FP40);

    glMatrixMode(GL_PROJECTION);
    glPopMatrix();
    glMatrixMode(GL_MODELVIEW);
    glPopMatrix();
    glPopAttrib();
    glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);

    // _DEBUG
    /*
    {
        glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, sort_fbo[_destSortIndex]);
        static float debug[256];
        glReadPixels(0, 0, _width, _height, GL_RGB, GL_FLOAT, (float*)debug);
        TRACE("[%d]", _currentSortIndex);
        for (int i = 0; i < _width * _height * 3; i += 3)
            TRACE("%.2f, %.2f, %.2f", debug[i], debug[i+1], debug[i+2]);
        glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);
    }
    */

    // _DEBUG
    /*
    {
        glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, psys_fbo[_currentPosIndex]);
        static float debug[256];
        glReadPixels(0, 0, _width, _height, GL_RGB, GL_FLOAT, (float*)debug);
        TRACE("currentPos[%d]", _currentPosIndex);
        for (int i = 0; i < _width * _height * 3; i += 3)
            TRACE("%.2f, %.2f, %.2f", debug[i], debug[i+1], debug[i+2]);
        glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);
    }
    */

    // compute distance
    swap(_currentSortIndex, _destSortIndex);

    // END - COMPUTE DISTANCE
    ///////////////////////////////////////////////////////////

    ///////////////////////////////////////////////////////////
    // BEGIN - MERGE SORT
    _currentSortPass = 0;

    int logdSize = logd(_particleMaxCount);
    _maxSortPasses = (logdSize + 1) * logdSize / 2;

    _sortBegin = _sortEnd;
    _sortEnd = (_sortBegin + _sortPassesPerFrame) % _maxSortPasses;

    cgGLSetParameter2f(_srSizeParam, (float)_width, (float)_height);
    cgGLSetParameter2f(_seSizeParam, (float)_width, (float)_height);

    mergeSort(this->_particleMaxCount);

    // _DEBUG
    /*
    {
        glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, sort_fbo[_currentSortIndex]);
        static float debug[256];
        glReadPixels(0, 0, _width, _height, GL_RGB, GL_FLOAT, (float*)debug);
        TRACE("[%d]", _currentSortIndex);
        for (int i = 0; i < _width * _height * 3; i += 3)
            TRACE("%.2f, %.2f, %.2f", debug[i], debug[i+1], debug[i+2]);
        glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);
    }
    */

    // END - MERGE SORT
    ///////////////////////////////////////////////////////////

    ///////////////////////////////////////////////////////////
    // POSITION LOOKUP
    glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, psys_fbo[_destPosIndex]);
    cgGLBindProgram(_distanceSortLookupFP);
    cgGLEnableProfile(CG_PROFILE_FP40);

    glActiveTextureARB(GL_TEXTURE0_ARB);
    glBindTexture(GL_TEXTURE_RECTANGLE_ARB, sort_tex[_currentSortIndex]);

    glActiveTextureARB(GL_TEXTURE1_ARB);
    glBindTexture(GL_TEXTURE_RECTANGLE_ARB, psys_tex[_currentPosIndex]);

    glPushAttrib(GL_VIEWPORT_BIT);
    glViewport(0, 0, _width, _height);
    glMatrixMode(GL_PROJECTION);
    glPushMatrix();
    glLoadIdentity();
    glOrtho(0, _width, 0, _height, -10.0f, 10.0f);
    glMatrixMode(GL_MODELVIEW);
    glPushMatrix();
    glLoadIdentity();

    drawQuad();

    glMatrixMode(GL_PROJECTION);
    glPopMatrix();
    glMatrixMode(GL_MODELVIEW);
    glPopMatrix();
    glPopAttrib();

    glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);
    cgGLDisableProfile(CG_PROFILE_FP40);

    // POSITION LOOKUP
    ///////////////////////////////////////////////////////////
    glActiveTextureARB(GL_TEXTURE1_ARB);
    glDisable(GL_TEXTURE_RECTANGLE_ARB);

    glActiveTextureARB(GL_TEXTURE0_ARB);
    glDisable(GL_TEXTURE_RECTANGLE_ARB);

    // _DEBUG
    /*
    {
        glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, psys_fbo[_destPosIndex]);
        static float debug[256];
        glReadPixels(0, 0, _width, _height, GL_RGB, GL_FLOAT, (float*)debug);
        TRACE("[%d]", _currentSortIndex);
        for (int i = 0; i < _width * _height * 3; i += 3)
            TRACE("%.2f, %.2f, %.2f", debug[i], debug[i+1], debug[i+2]);
        glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);
    }
    */
}

void ParticleSystem::mergeSort(int count)
{
    if (count > 1) {
        mergeSort(count >> 1);
        merge(count, 1);
    }
}

void ParticleSystem::merge(int count, int step)
{
    if (count > 2) {
        merge(count >> 1, step << 1);

        ++_currentSortPass;

        if (_sortBegin < _sortEnd) {
            if (_currentSortPass < _sortBegin || _currentSortPass >= _sortEnd)
                return;
        } else {
            if (_currentSortPass < _sortBegin && _currentSortPass >= _sortEnd)
                return;
        }

        glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, sort_fbo[_destSortIndex]);
        cgGLBindProgram(_sortRecursionFP);
        cgGLEnableProfile(CG_PROFILE_FP40);

        glActiveTextureARB(GL_TEXTURE0_ARB);
        glBindTexture(GL_TEXTURE_RECTANGLE_ARB , sort_tex[_currentSortIndex]);

        cgGLSetParameter1f(_srStepParam, (float)step);
        cgGLSetParameter1f(_srCountParam, (float)count);

        glPushAttrib(GL_VIEWPORT_BIT);
        glViewport(0, 0, _width, _height);
        glMatrixMode(GL_PROJECTION);
        glPushMatrix();
        glLoadIdentity();
        glOrtho(0, _width, 0, _height, -10.0f, 10.0f);
        glMatrixMode(GL_MODELVIEW);
        glPushMatrix();
        glLoadIdentity();

        drawQuad();

        glMatrixMode(GL_PROJECTION);
        glPopMatrix();
        glMatrixMode(GL_MODELVIEW);
        glPopMatrix();
        glPopAttrib();

        cgGLDisableProfile(CG_PROFILE_FP40);

        glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);
        glBindTexture(GL_TEXTURE_RECTANGLE_ARB , 0);
    } else {
        _currentSortPass++;

        if (_sortBegin < _sortEnd) {
            if (_currentSortPass < _sortBegin || _currentSortPass >= _sortEnd)
                return;
        } else {
            if (_currentSortPass < _sortBegin && _currentSortPass >= _sortEnd)
                return;
        }

        glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, sort_fbo[_destSortIndex]);
        cgGLBindProgram(_sortEndFP);
        cgGLEnableProfile(CG_PROFILE_FP40);

        glActiveTextureARB(GL_TEXTURE0_ARB);
        glBindTexture(GL_TEXTURE_RECTANGLE_ARB , sort_tex[_currentSortIndex]);

        cgGLSetParameter1f(_seStepParam, (float)step);

        glPushAttrib(GL_VIEWPORT_BIT);
        glViewport(0, 0, _width, _height);
        glMatrixMode(GL_PROJECTION);
        glPushMatrix();
        glLoadIdentity();
        glOrtho(0, _width, 0, _height, -10.0f, 10.0f);
        glMatrixMode(GL_MODELVIEW);
        glPushMatrix();
        glLoadIdentity();

        drawQuad();

        glMatrixMode(GL_PROJECTION);
        glPopMatrix();
        glMatrixMode(GL_MODELVIEW);
        glPopMatrix();
        glPopAttrib();

        cgGLDisableProfile(CG_PROFILE_FP40);

        glBindTexture(GL_TEXTURE_RECTANGLE_ARB , 0);
        glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);
    }

    swap(_currentSortIndex, _destSortIndex);
}

void ParticleSystem::renderStreamlines()
{
    if (_currentStreamlineIndex > 2) {
        glPushMatrix();
        glScalef(_scalex, _scaley, _scalez);
        glTranslatef(-0.5f, -0.5f, -0.5f);

        if (_drawBBoxEnabled) drawUnitBox();

        glColor3f(1.0f, 0.0f, 0.0f);
        glEnableClientState(GL_VERTEX_ARRAY);
        //glEnableClientState(GL_COLOR_ARRAY);

        _streamVertices->setPointer(0);
        //glColorPointer(4, GL_FLOAT, 0, 0);

        ::glDrawElements(GL_LINES, _particleCount * 2 * (_currentStreamlineIndex - 1),
                         GL_UNSIGNED_INT, _indexBuffer);
        glDisableClientState(GL_VERTEX_ARRAY);
        glPopMatrix();
    }
}

void ParticleSystem::render()
{
    glPushMatrix();

    if (_streamlineEnabled) {
        renderStreamlines();
    } else {
        glScalef(_scalex, _scaley, _scalez);
        glTranslatef(-0.5f, -0.5f, -0.5f);
        if (_glyphEnabled) {
            if (_drawBBoxEnabled) drawUnitBox();
            glColor3f(1, 1, 1);

            glDepthMask(GL_FALSE);
            glEnable(GL_BLEND);

#ifndef USE_RGBA_ARROW
            glBlendFunc(GL_SRC_ALPHA, GL_ONE);
#else
            glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
#endif
            glEnable(GL_ALPHA_TEST);
            glAlphaFunc(GL_GREATER, 0.6);

            glEnable(GL_POINT_SPRITE_ARB);
            glPointSize(_pointSize);

            glEnable(GL_VERTEX_PROGRAM_POINT_SIZE_ARB);

#ifndef TEST
            _arrows->activate();
            glEnable(GL_TEXTURE_2D);
            glPointParameterfARB(GL_POINT_FADE_THRESHOLD_SIZE_ARB, 0.0f);

            glPointParameterfARB(GL_POINT_SIZE_MIN_ARB, 1.0f);
            glPointParameterfARB(GL_POINT_SIZE_MAX_ARB, 100.0f);
            glTexEnvi(GL_POINT_SPRITE_ARB, GL_COORD_REPLACE_ARB, GL_TRUE);

            cgGLBindProgram(_particleVP);
            cgGLBindProgram(_particleFP);
            cgGLEnableProfile(CG_PROFILE_VP40);
            cgGLEnableProfile(CG_PROFILE_FP40);

            cgSetParameter1f(_mvCurrentTimeParam, _currentTime);
            //TRACE("%f %f, %f %d", _fov, tan(_fov), tan(_fov / 2.0), _screenHeight);
            //cgSetParameter1f(_mvTanHalfFOVParam, -tan(_fov * M_PI / 180 * 0.5) * _screenHeight * 0.5);
            //float v = tan(_fov * M_PI / 180 * 0.5) * _screenHeight * 0.5;
            cgSetParameter1f(_mvTanHalfFOVParam, tan(_fov * M_PI / 180 * 0.5) * _screenHeight * 0.5);
            //cgSetParameter1f(_mvTanHalfFOVParam,  _screenHeight * 0.5 / tan(_fov * M_PI / 180 * 0.5));

            cgGLSetStateMatrixParameter(_mvpParticleParam,
                                        CG_GL_MODELVIEW_PROJECTION_MATRIX,
                                        CG_GL_MATRIX_IDENTITY);
            cgGLSetStateMatrixParameter(_mvParticleParam,
                                        CG_GL_MODELVIEW_MATRIX,
                                        CG_GL_MATRIX_IDENTITY);

            // TBD..
            glPushClientAttrib(GL_CLIENT_VERTEX_ARRAY_BIT);			
            glEnableVertexAttribArrayARB(8);
            glEnableClientState(GL_VERTEX_ARRAY);
            //glEnableClientState(GL_COLOR_ARRAY);
            _vertices->setPointer(0);
            //glBindBufferARB(GL_ARRAY_BUFFER, _colorBufferID);
            //glColorPointer(4, GL_FLOAT, 0, 0);
            //glBindBufferARB(GL_ARRAY_BUFFER, 0);

            // TBD...
            glDrawArrays(GL_POINTS, 0, this->_particleMaxCount);
            glPointSize(1);

            glDisableClientState(GL_VERTEX_ARRAY);
            //glDisableClientState(GL_COLOR_ARRAY);

            // TBD...
            ::glDisableVertexAttribArray(8);
            glPopClientAttrib();

            cgGLDisableProfile(CG_PROFILE_VP40);
            cgGLDisableProfile(CG_PROFILE_FP40);

            glDepthMask(GL_TRUE);

            glDisable(GL_POINT_SPRITE_ARB);
            glDisable(GL_VERTEX_PROGRAM_POINT_SIZE_ARB);

            glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
            glDisable(GL_BLEND);
#else
            glBindTexture(GL_TEXTURE_2D, ::SpotTexID);
            glEnable(GL_TEXTURE_2D);
            //glPointParameterfARB(GL_POINT_FADE_THRESHOLD_SIZE_ARB, 60.0f);
            glPointParameterfARB(GL_POINT_FADE_THRESHOLD_SIZE_ARB, 0.0f);

            glPointParameterfARB(GL_POINT_SIZE_MIN_ARB, 1.0f);
            glPointParameterfARB(GL_POINT_SIZE_MAX_ARB, 100.0f);
            glTexEnvi(GL_POINT_SPRITE_ARB, GL_COORD_REPLACE_ARB, GL_TRUE);

            glEnableClientState(GL_VERTEX_ARRAY);
            //glEnableClientState(GL_COLOR_ARRAY);
            _vertices->setPointer(0);
            //glBindBufferARB(GL_ARRAY_BUFFER, _colorBufferID);
            //glColorPointer(4, GL_FLOAT, 0, 0);
            //glBindBufferARB(GL_ARRAY_BUFFER, 0);

            // TBD...
            glDrawArrays(GL_POINTS, 0, this->_particleMaxCount);
            glPointSize(1);
            glDrawArrays(GL_POINTS, 0, this->_particleMaxCount);

            glDisableClientState(GL_VERTEX_ARRAY);

            glDepthMask(GL_TRUE);

            glDisable(GL_POINT_SPRITE_ARB);
            glDisable(GL_VERTEX_PROGRAM_POINT_SIZE_ARB);

            glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
            glDisable(GL_BLEND);
#endif
        } else {
            if (_drawBBoxEnabled) drawUnitBox();

            glColor3f(1, 1, 1);
            glEnableClientState(GL_VERTEX_ARRAY);
            //glEnableClientState(GL_COLOR_ARRAY);
            glPointSize(10);
            _vertices->setPointer(0);
            //glBindBufferARB(GL_ARRAY_BUFFER, _colorBufferID);
            //glColorPointer(4, GL_FLOAT, 0, 0);
            //glBindBufferARB(GL_ARRAY_BUFFER, 0);
            glDrawArrays(GL_POINTS, 0, _particleMaxCount);

            glPointSize(1);
            _vertices->setPointer(0);
            //glBindBufferARB(GL_ARRAY_BUFFER, _colorBufferID);
            //glColorPointer(4, GL_FLOAT, 0, 0);
            //glBindBufferARB(GL_ARRAY_BUFFER, 0);
            glDrawArrays(GL_POINTS, 0, _particleMaxCount);

            glDisableClientState(GL_VERTEX_ARRAY);
        }

#ifdef notdef
        if (_criticalPoints && _criticalPoints->size()) {
            std::vector<vrmath::Vector3f>::iterator iter;
            glColor4f(1, 1, 1, 1);
            glPointSize(10);
            glBegin(GL_POINTS);
            for (iter = _criticalPoints->begin(); iter != _criticalPoints->end(); ++iter) {
                glVertex3f((*iter).x, (*iter).y, (*iter).z);
            }
            glEnd();
            glPointSize(1);
        }
#endif
    }

    glPopMatrix();
}

void ParticleSystem::drawQuad(int x1, int y1, int x2, int y2)
{
    glBegin(GL_QUADS);

    glTexCoord2f(x1, y1);
    glVertex2f(x1, y1);

    glTexCoord2f(x2, y1);
    glVertex2f(x2, y1);

    glTexCoord2f(x2, y2); 
    glVertex2f(x2, y2);

    glTexCoord2f(x1, y2);
    glVertex2f(x1, y2);

    glEnd();
}

void ParticleSystem::drawQuad()
{
    glBegin(GL_QUADS);

    glTexCoord2f(0, 0);
    glVertex2f(0, 0);

    glTexCoord2f((float)_width, 0);
    glVertex2f((float)_width, 0);

    glTexCoord2f((float)_width, (float)_height); 
    glVertex2f((float)_width, (float)_height);

    glTexCoord2f(0, (float)_height);
    glVertex2f(0, (float)_height);

    glEnd();
}

void ParticleSystem::addEmitter(ParticleEmitter* emitter)
{
    _emitters.push_back(emitter);
}

void ParticleSystem::removeEmitter(int index)
{
    // TBD...
}

void ParticleSystem::removeAllEmitters()
{
    std::vector<ParticleEmitter*>::iterator iter;
    for (iter = _emitters.begin(); iter != _emitters.end(); ++iter) {
        delete *iter;
    }
    _emitters.clear();
}

void ParticleSystem::drawUnitBox()
{
    float x0 = 0.0f, y0 = 0.0f, z0 = 0.0f;
    float x1 = 1.0f, y1 = 1.0f, z1 = 1.0f;
    float r = 1.0f, g = 1.0f, b = 0.0f;
    float line_width = 2.0f;
    glEnable(GL_DEPTH_TEST);
    glDisable(GL_TEXTURE_2D);
    glEnable(GL_BLEND);

    glColor4d(r, g, b, 1.0);
    glLineWidth(line_width);

    glBegin(GL_LINE_LOOP);
    {
        glVertex3d(x0, y0, z0);
        glVertex3d(x1, y0, z0);
        glVertex3d(x1, y1, z0);
        glVertex3d(x0, y1, z0);
    }
    glEnd();

    glBegin(GL_LINE_LOOP);
    {
        glVertex3d(x0, y0, z1);
        glVertex3d(x1, y0, z1);
        glVertex3d(x1, y1, z1);
        glVertex3d(x0, y1, z1);
    }
    glEnd();

    glBegin(GL_LINE_LOOP);
    {
        glVertex3d(x0, y0, z0);
        glVertex3d(x0, y0, z1);
        glVertex3d(x0, y1, z1);
        glVertex3d(x0, y1, z0);
    }
    glEnd();

    glBegin(GL_LINE_LOOP);
    {
        glVertex3d(x1, y0, z0);
        glVertex3d(x1, y0, z1);
        glVertex3d(x1, y1, z1);
        glVertex3d(x1, y1, z0);
    }
    glEnd();
    glLineWidth(1.0f);
}

void ParticleSystem::setUserDefinedNumOfParticles(int numParticles)
{
    if (numParticles < _particleMaxCount)
        _userDefinedParticleMaxCount = numParticles;
    else
        _userDefinedParticleMaxCount = _particleMaxCount;
    reset();
}