source: Swollen/swollen/spotlight.cpp @ 31

#include <math.h>
#include <spotlight.h>
#include <osg/ShapeDrawable>
#include <iostream>

#define DEF_DEFAULT_ANGLE 45
#define DEF_DEFAULT_EXPONENT 10
#define DEF_DEFAULT_CONE_RADIUS 0.05
#define DEF_DEFAULT_CONE_HEIGHT 0.1


SpotLight::SpotLight(osg::StateSet* rootStateSet, int num)
{
    // positioning container
    _group = new osg::MatrixTransform;
    _group->setCullingActive(false);

    // OpenGL light
    _light = new osg::Light;
    _light->setLightNum(num);
    _light->setPosition(osg::Vec4(0,0,0,1));
    _light->setAmbient(osg::Vec4(0.5,0.5,0.5,1));
    _light->setDiffuse(osg::Vec4(1,1,1,1));
    _light->setSpotCutoff(DEF_DEFAULT_ANGLE);
    _light->setSpotExponent(DEF_DEFAULT_EXPONENT);

    // Scenegraph node
    _source = new osg::LightSource;
    _source->setReferenceFrame( osg::LightSource::RELATIVE_TO_PARENTS );
    _source->setLight(_light);
    _source->setLocalStateSetModes( osg::StateAttribute::ON ); 
    _source->setStateSetModes( *rootStateSet, osg::StateAttribute::ON );
    _group->addChild( _source );

    // create cone marker for spotlight and rotate towards origin
    _marker = new osg::Geode;
    _shape = new osg::Cone;
    _shape->setRadius(DEF_DEFAULT_CONE_RADIUS);
    _shape->setHeight(DEF_DEFAULT_CONE_HEIGHT);
    _shape->setCenter( osg::Vec3(0,0,0) );
    _marker->addDrawable( new osg::ShapeDrawable(_shape) );
    _group->addChild(_marker);

    setPosition( osg::Vec3(0,0,1) );  // default overhead
}


void SpotLight::setSpotAngle( float degrees )
{
    _light->setSpotCutoff( degrees );
    float radians = degrees * osg::PI / 180.0;
    float cone_radius = tan( radians/2.0 ) * _shape->getHeight();
    _shape->setRadius( cone_radius );
}


void SpotLight::setPosition(osg::Vec3 v)
{
    osg::Vec3 origindir;
    osg::Quat quat;
    origindir.set( -v );
    origindir.normalize();
    quat.makeRotate( osg::Vec3(0,0,-1), origindir );

    _group->setMatrix( osg::Matrix::rotate( quat ) * osg::Matrix::translate(v) );
}



SpotLight::~SpotLight()
{
}