/* -*-c++-*- OpenSceneGraph - Copyright (C) 1998-2006 Robert Osfield 
 *
 * This application is open source and may be redistributed and/or modified   
 * freely and without restriction, both in commericial and non commericial applications,
 * as long as this copyright notice is maintained.
 * 
 * This application is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
*/

#include <osgDB/ReadFile>
#include <osgUtil/Optimizer>
#include <osgProducer/Viewer>

class MotionBlurDrawCallback: public osgProducer::OsgSceneHandler::Callback
{
public:
    MotionBlurDrawCallback(double persistence)
    :    cleared_(false),
        persistence_(persistence)
    {
    }

    virtual void operator()(osgProducer::OsgSceneHandler &handler, Producer::Camera &camera)
    {
        double t = handler.getSceneView()->getFrameStamp()->getReferenceTime();

        if (!cleared_)
        {
            // clear the accumulation buffer
            glClearColor(0, 0, 0, 0);
            glClear(GL_ACCUM_BUFFER_BIT);
            cleared_ = true;
            t0_ = t;
        }

        double dt = fabs(t - t0_);
        t0_ = t;

        // call the scene handler's draw function
        handler.drawImplementation(camera);        

        // compute the blur factor
        double s = powf(0.2, dt / persistence_);

        // scale, accumulate and return
        glAccum(GL_MULT, s);
        glAccum(GL_ACCUM, 1 - s);
        glAccum(GL_RETURN, 1.0f);
    }

private:
    bool cleared_;
    double t0_;
    double persistence_;
};


int main( int argc, char **argv )
{

    // use an ArgumentParser object to manage the program arguments.
    osg::ArgumentParser arguments(&argc,argv);
    
    // set up the usage document, in case we need to print out how to use this program.
    arguments.getApplicationUsage()->setApplicationName(arguments.getApplicationName());
    arguments.getApplicationUsage()->setDescription(arguments.getApplicationName()+" is an OpenSceneGraph example that shows how to use the accumulation buffer to achieve a simple motion blur effect.");
    arguments.getApplicationUsage()->setCommandLineUsage(arguments.getApplicationName()+" [options] filename ...");
    arguments.getApplicationUsage()->addCommandLineOption("-h or --help","Display this information");
    arguments.getApplicationUsage()->addCommandLineOption("-P or --persistence","Set the motion blur persistence time");
    

    // construct the viewer.
    osgProducer::Viewer viewer(arguments);

    // set up the value with sensible default event handlers.
    viewer.setUpViewer(osgProducer::Viewer::STANDARD_SETTINGS);

    // get details on keyboard and mouse bindings used by the viewer.
    viewer.getUsage(*arguments.getApplicationUsage());

    // if user request help write it out to cout.
    if (arguments.read("-h") || arguments.read("--help"))
    {
        arguments.getApplicationUsage()->write(std::cout);
        return 1;
    }

    double persistence = 0.25;
    arguments.read("-P", persistence) || arguments.read("--persistence", persistence);

    // report any errors if they have occured when parsing the program aguments.
    if (arguments.errors())
    {
        arguments.writeErrorMessages(std::cout);
        return 1;
    }
    
    if (arguments.argc()<=1)
    {
        arguments.getApplicationUsage()->write(std::cout,osg::ApplicationUsage::COMMAND_LINE_OPTION);
        return 1;
    }

    osg::Timer_t start_tick = osg::Timer::instance()->tick();

    // read the scene from the list of file specified commandline args.
    osg::ref_ptr<osg::Node> loadedModel = osgDB::readNodeFiles(arguments);

    // if no model has been successfully loaded report failure.
    if (!loadedModel) 
    {
        std::cout << arguments.getApplicationName() <<": No data loaded" << std::endl;
        return 1;
    }

    // any option left unread are converted into errors to write out later.
    arguments.reportRemainingOptionsAsUnrecognized();

    // report any errors if they have occured when parsing the program aguments.
    if (arguments.errors())
    {
        arguments.writeErrorMessages(std::cout);
    }

    osg::Timer_t end_tick = osg::Timer::instance()->tick();

    std::cout << "Time to load = "<<osg::Timer::instance()->delta_s(start_tick,end_tick)<<std::endl;

    // set the display settings we can to request, OsgCameraGroup will read this.
    osg::DisplaySettings::instance()->setMinimumNumAccumBits(8,8,8,8);

    // optimize the scene graph, remove rendundent nodes and state etc.
    osgUtil::Optimizer optimizer;
    optimizer.optimize(loadedModel.get());

    // pass the loaded scene graph to the viewer.
    viewer.setSceneData(loadedModel.get());

    // create the windows and run the threads.
    viewer.realize();

    // set our motion blur callback as the draw callback for each scene handler
    osgProducer::Viewer::SceneHandlerList &shl = viewer.getSceneHandlerList();
    for (osgProducer::Viewer::SceneHandlerList::iterator i=shl.begin(); i!=shl.end(); ++i)
    {
        (*i)->setDrawCallback(new MotionBlurDrawCallback(persistence));
    }

    while( !viewer.done() )
    {
        // wait for all cull and draw threads to complete.
        viewer.sync();

        // update the scene by traversing it with the the update visitor which will
        // call all node update callbacks and animations.
        viewer.update();
         
        // fire off the cull and draw traversals of the scene.
        viewer.frame();
        
    }
    
    // wait for all cull and draw threads to complete before exit.
    viewer.sync();

    return 0;
}