/* OpenSceneGraph example, osgthirdpersonview.
*
*  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.
*/
// This code is originally Copyright (c) 2008 Skew Matrix  Software LLC,
// but you may use the code under the terms of the OSGPL as described above.

// This example demonstrates how CompositeViewer can be used to
// provide a third person view of another view, including eyepoint and
// view frustum.
//
// The code creates a CompositeViewer with two Views. Each of the two
// Views has its own window. One View is the typical scene view,
// showing the loaded model(s).
//
// The second View is a third person view showing not just the loaded
// model(s), but also a wireframe representation of the first View's
// frustum. Interactions with the first View are reflect5ed in the
// second View's displayed frustum.
//
// Command line arguments are taken to be models for display. If you
// specify no command line arguments, the code attempts to load cow.osg.


#include <osg/Geometry>
#include <osg/DisplaySettings>
#include <osg/MatrixTransform>
#include <osg/LineWidth>
#include <osgDB/ReadFile>
#include <osgViewer/CompositeViewer>
#include <osgGA/TrackballManipulator>


// Given a Camera, create a wireframe representation of its
// view frustum. Create a default representation if camera==NULL.
osg::Node*
makeFrustumFromCamera( osg::Camera* camera )
{
    // Projection and ModelView matrices
    osg::Matrixd proj;
    osg::Matrixd mv;
    if (camera)
    {
        proj = camera->getProjectionMatrix();
        mv = camera->getViewMatrix();
    }
    else
    {
        // Create some kind of reasonable default Projection matrix.
        proj.makePerspective( 30., 1., 1., 10. );
        // leave mv as identity
    }

    // Get near and far from the Projection matrix.
    const double near = proj(3,2) / (proj(2,2)-1.0);
    const double far = proj(3,2) / (1.0+proj(2,2));

    // Get the sides of the near plane.
    const double nLeft = near * (proj(2,0)-1.0) / proj(0,0);
    const double nRight = near * (1.0+proj(2,0)) / proj(0,0);
    const double nTop = near * (1.0+proj(2,1)) / proj(1,1);
    const double nBottom = near * (proj(2,1)-1.0) / proj(1,1);

    // Get the sides of the far plane.
    const double fLeft = far * (proj(2,0)-1.0) / proj(0,0);
    const double fRight = far * (1.0+proj(2,0)) / proj(0,0);
    const double fTop = far * (1.0+proj(2,1)) / proj(1,1);
    const double fBottom = far * (proj(2,1)-1.0) / proj(1,1);

    // Our vertex array needs only 9 vertices: The origin, and the
    // eight corners of the near and far planes.
    osg::Vec3Array* v = new osg::Vec3Array;
    v->resize( 9 );
    (*v)[0].set( 0., 0., 0. );
    (*v)[1].set( nLeft, nBottom, -near );
    (*v)[2].set( nRight, nBottom, -near );
    (*v)[3].set( nRight, nTop, -near );
    (*v)[4].set( nLeft, nTop, -near );
    (*v)[5].set( fLeft, fBottom, -far );
    (*v)[6].set( fRight, fBottom, -far );
    (*v)[7].set( fRight, fTop, -far );
    (*v)[8].set( fLeft, fTop, -far );

    osg::Geometry* geom = new osg::Geometry;
    geom->setUseDisplayList( false );
    geom->setVertexArray( v );

    osg::Vec4Array* c = new osg::Vec4Array;
    c->push_back( osg::Vec4( 1., 1., 1., 1. ) );
    geom->setColorArray( c );
    geom->setColorBinding( osg::Geometry::BIND_OVERALL );

    GLushort idxLines[8] = {
        0, 5, 0, 6, 0, 7, 0, 8 };
    GLushort idxLoops0[4] = {
        1, 2, 3, 4 };
    GLushort idxLoops1[4] = {
        5, 6, 7, 8 };
    geom->addPrimitiveSet( new osg::DrawElementsUShort( osg::PrimitiveSet::LINES, 8, idxLines ) );
    geom->addPrimitiveSet( new osg::DrawElementsUShort( osg::PrimitiveSet::LINE_LOOP, 4, idxLoops0 ) );
    geom->addPrimitiveSet( new osg::DrawElementsUShort( osg::PrimitiveSet::LINE_LOOP, 4, idxLoops1 ) );

    osg::Geode* geode = new osg::Geode;
    geode->addDrawable( geom );

    geode->getOrCreateStateSet()->setMode( GL_LIGHTING, osg::StateAttribute::OFF | osg::StateAttribute::PROTECTED );


    // Create parent MatrixTransform to transform the view volume by
    // the inverse ModelView matrix.
    osg::MatrixTransform* mt = new osg::MatrixTransform;
    mt->setMatrix( osg::Matrixd::inverse( mv ) );
    mt->addChild( geode );

    return mt;
}


int
main( int argc,
      char ** argv )
{
    osg::ArgumentParser arguments( &argc, argv );

    osg::ref_ptr< osg::Group > root = new osg::Group;

    // Child 0: We'll replace this every frame with an updated representation
    //   of the view frustum.
    root->addChild( makeFrustumFromCamera( NULL ) );

    osg::ref_ptr< osg::Node > scene;
    scene = osgDB::readNodeFiles( arguments );
    if (!scene)
    {
        // User didn't specify anything, or file(s) didn't exist.
        // Try to load the cow...
        osg::notify( osg::WARN ) << arguments.getApplicationName() << ": Could not find specified files. Trying \"cow.osg\" instead." << std::endl;
        if ( !(scene = osgDB::readNodeFile( std::string( "cow.osg" ) ) ) )
        {
            osg::notify( osg::FATAL ) << arguments.getApplicationName() << ": No data loaded." << std::endl;
            return 1;
        }
    }
    root->addChild( scene.get() );


    osgViewer::CompositeViewer viewer( arguments );
    // Turn on FSAA, makes the lines look better.
    osg::DisplaySettings::instance()->setNumMultiSamples( 4 );

    // Create View 0 -- Just the loaded model.
    {
        osgViewer::View* view = new osgViewer::View;
        viewer.addView( view );

        view->setUpViewInWindow( 10, 10, 640, 480 );
        view->setSceneData( scene.get() );
        view->setCameraManipulator( new osgGA::TrackballManipulator );
    }
    
    // Create view 1 -- Contains the loaded moel, as well as a wireframe frustum derived from View 0's Camera.
    {
        osgViewer::View* view = new osgViewer::View;
        viewer.addView( view );

        view->setUpViewInWindow( 10, 510, 640, 480 );
        view->setSceneData( root.get() );
        view->setCameraManipulator( new osgGA::TrackballManipulator );
    }

    while (!viewer.done())
    {
        // Update the wireframe frustum
        root->removeChild( 0, 1 );
        root->insertChild( 0, makeFrustumFromCamera(
                viewer.getView( 0 )->getCamera() ) );

        viewer.frame();
    }
    return 0;
}

