//By smells2 at Lab 2012-02-21
#include <osg/Group>
#include <osg/Geode>
#include <osg/ShapeDrawable>
#include <osg/Texture2D>
#include <osgViewer/Viewer>
#include <osgDB/readfile>

#include <osg/PositionAttitudeTransform>
#include <osg/TexEnv>
#include <osg/Texture2D>
#include <iostream>
int main()
{
osg::ref_ptr<osg::Group> root = new osg::Group;
osgViewer::Viewer myViewer;

//Declear Sphere instance,the constructor takes an osg::vec3 to define
//center and a float to define the radius.
//Then we declear the ShapDrawable instance that derive from Drawable .We should
//initalize it with the shape we create above .
osg::ref_ptr<osg::Geode> unitSphere = new osg::Geode;
osg::ref_ptr<osg::Sphere> sphere = new osg::Sphere(osg::Vec3(0,0,0), 1.0f);
osg::ref_ptr<osg::ShapeDrawable> shapeDrawable = new osg::ShapeDrawable(sphere.get());
unitSphere->addDrawable(shapeDrawable.get());
osg::ref_ptr<osg::PositionAttitudeTransform> sphereForm = new osg::PositionAttitudeTransform;
sphereForm->setPosition(osg::Vec3(2.5,0.0,0.0));
sphereForm->addChild(unitSphere.get());
root->addChild(sphereForm.get());

//load image from the file
osg::ref_ptr<osg::Texture2D> earthTexture = new osg::Texture2D;
earthTexture->setDataVariance(osg::Object::DYNAMIC);
osg::ref_ptr<osg::Image> earthImage = osgDB::readImageFile("D:\\OSG\\osg2.9\\OpenSceneGraph2.9.5\\data\\Images\\land_shallow_topo_2048.jpg");
if (!earthImage.get())
{
std::cout<<"load texture failed !"<<std::endl;
return -1;
}

//assign the texture from the image file
earthTexture->setImage(earthImage.get());

//set the stateset for decal texture
osg::ref_ptr<osg::TexEnv> texenv = new osg::TexEnv;
osg::ref_ptr<osg::StateSet> stateset = new osg::StateSet;
texenv->setMode(osg::TexEnv::DECAL);
stateset->setTextureAttributeAndModes(0,earthTexture.get(),osg::StateAttribute::ON);
stateset->setTextureAttribute(0,texenv.get());

//realize
root->setStateSet(stateset.get());
myViewer.setSceneData(root.get());
myViewer.realize();
myViewer.run();
}

osg绘制一个球体