OpenSceneGraph/examples/osghud/osghud.cpp

/* -*-c++-*- OpenSceneGraph - Copyright (C) 1998-2006 Robert Osfield 
 *
 * This library is open source and may be redistributed and/or modified under  
 * the terms of the OpenSceneGraph Public License (OSGPL) version 0.0 or 
 * (at your option) any later version.  The full license is in LICENSE file
 * included with this distribution, and on the openscenegraph.org website.
 * 
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the 
 * OpenSceneGraph Public License for more details.
*/

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

#include <osg/Material>
#include <osg/Geode>
#include <osg/BlendFunc>
#include <osg/Depth>
#include <osg/PolygonOffset>
#include <osg/MatrixTransform>
#include <osg/Camera>

#include <osgText/Text>


osg::Node* createHUD()
{
    osg::Geode* geode = new osg::Geode();
    
    std::string timesFont("fonts/arial.ttf");

    // turn lighting off for the text and disable depth test to ensure its always ontop.
    osg::StateSet* stateset = geode->getOrCreateStateSet();
    stateset->setMode(GL_LIGHTING,osg::StateAttribute::OFF);

    osg::Vec3 position(150.0f,800.0f,0.0f);
    osg::Vec3 delta(0.0f,-120.0f,0.0f);

    {
        osgText::Text* text = new  osgText::Text;
        geode->addDrawable( text );

        text->setFont(timesFont);
        text->setPosition(position);
        text->setText("Head Up Displays are simple :-)");
        
        position += delta;
    }    


    {
        osgText::Text* text = new  osgText::Text;
        geode->addDrawable( text );

        text->setFont(timesFont);
        text->setPosition(position);
        text->setText("All you need to do is create your text in a subgraph.");
        
        position += delta;
    }    


    {
        osgText::Text* text = new  osgText::Text;
        geode->addDrawable( text );

        text->setFont(timesFont);
        text->setPosition(position);
        text->setText("Then place an osg::Camera above the subgraph\n"
                      "to create an orthographic projection.\n");
        
        position += delta;
    } 
    
    {
        osgText::Text* text = new  osgText::Text;
        geode->addDrawable( text );

        text->setFont(timesFont);
        text->setPosition(position);
        text->setText("Set the Camera's ReferenceFrame to ABSOLUTE_RF to ensure\n"
                      "it remains independent from any external model view matrices.");
        
        position += delta;
    } 

    {
        osgText::Text* text = new  osgText::Text;
        geode->addDrawable( text );

        text->setFont(timesFont);
        text->setPosition(position);
        text->setText("And set the Camera's clear mask to just clear the depth buffer.");
        
        position += delta;
    }    

    {
        osgText::Text* text = new  osgText::Text;
        geode->addDrawable( text );

        text->setFont(timesFont);
        text->setPosition(position);
        text->setText("And finally set the Camera's RenderOrder to POST_RENDER\n"
                      "to make sure its drawn last.");
        
        position += delta;
    }    
    
    
    {
        osg::BoundingBox bb;
        for(unsigned int i=0;i<geode->getNumDrawables();++i)
        {
            bb.expandBy(geode->getDrawable(i)->getBound());
        }

        osg::Geometry* geom = new osg::Geometry;

        osg::Vec3Array* vertices = new osg::Vec3Array;
        float depth = bb.zMin()-0.1;
        vertices->push_back(osg::Vec3(bb.xMin(),bb.yMax(),depth));
        vertices->push_back(osg::Vec3(bb.xMin(),bb.yMin(),depth));
        vertices->push_back(osg::Vec3(bb.xMax(),bb.yMin(),depth));
        vertices->push_back(osg::Vec3(bb.xMax(),bb.yMax(),depth));
        geom->setVertexArray(vertices);

        osg::Vec3Array* normals = new osg::Vec3Array;
        normals->push_back(osg::Vec3(0.0f,0.0f,1.0f));
        geom->setNormalArray(normals);
        geom->setNormalBinding(osg::Geometry::BIND_OVERALL);

        osg::Vec4Array* colors = new osg::Vec4Array;
        colors->push_back(osg::Vec4(1.0f,1.0,0.8f,0.2f));
        geom->setColorArray(colors);
        geom->setColorBinding(osg::Geometry::BIND_OVERALL);

        geom->addPrimitiveSet(new osg::DrawArrays(GL_QUADS,0,4));
        
        osg::StateSet* stateset = geom->getOrCreateStateSet();
        stateset->setMode(GL_BLEND,osg::StateAttribute::ON);
        //stateset->setAttribute(new osg::PolygonOffset(1.0f,1.0f),osg::StateAttribute::ON);
        stateset->setRenderingHint(osg::StateSet::TRANSPARENT_BIN);

        geode->addDrawable(geom);
    }

    osg::Camera* camera = new osg::Camera;

    // set the projection matrix
    camera->setProjectionMatrix(osg::Matrix::ortho2D(0,1280,0,1024));

    // set the view matrix    
    camera->setReferenceFrame(osg::Transform::ABSOLUTE_RF);
    camera->setViewMatrix(osg::Matrix::identity());

    // only clear the depth buffer
    camera->setClearMask(GL_DEPTH_BUFFER_BIT);

    // draw subgraph after main camera view.
    camera->setRenderOrder(osg::Camera::POST_RENDER);

    camera->addChild(geode);
    
    return camera;

}

int main( int argc, char **argv )
{
    // use an ArgumentParser object to manage the program arguments.
    osg::ArgumentParser arguments(&argc,argv);
    
    
    // read the scene from the list of file specified commandline args.
    osg::ref_ptr<osg::Node> scene = osgDB::readNodeFiles(arguments);

    osg::ref_ptr<osg::Group> group  = new osg::Group;
    
    // add the HUD subgraph.    
    if (scene.valid()) group->addChild(scene.get());
    group->addChild(createHUD());

    // construct the viewer.
    osgViewer::Viewer viewer;

    // set the scene to render
    viewer.setSceneData(group.get());

    return viewer.run();
}