#include <osgViewer/Viewer>

#include <osg/Node>
#include <osg/Geode>
#include <osg/Geometry>
#include <osg/Group>
#include <osg/Image>
#include <osg/TexGen>
#include <osg/Texture1D>
#include <osg/TexEnv>
#include <osg/StateSet>

#include <osgDB/ReadFile>
#include <osgDB/WriteFile>

#include <osgUtil/Optimizer>


//建立一個四邊形節點
osg::ref_ptr<osg::Node> createNode()
{
	osg::ref_ptr<osg::Geode> geode = new osg::Geode();
	osg::ref_ptr<osg::Geometry> geom = new osg::Geometry();

	//設定頂點
	osg::ref_ptr<osg::Vec3Array> vc = new osg::Vec3Array();
	vc->push_back(osg::Vec3(0.0f, 0.0f, 0.0f));
	vc->push_back(osg::Vec3(1.0f, 0.0f, 0.0f));
	vc->push_back(osg::Vec3(1.0f, 0.0f, 1.0f));
	vc->push_back(osg::Vec3(0.0f, 0.0f, 1.0f));

	geom->setVertexArray(vc.get());

	//設定紋理座標
	osg::ref_ptr<osg::Vec2Array> vt = new osg::Vec2Array();
	vt->push_back(osg::Vec2(0.0f, 0.0f));
	vt->push_back(osg::Vec2(1.0f, 0.0f));
	vt->push_back(osg::Vec2(1.0f, 1.0f));
	vt->push_back(osg::Vec2(0.0f, 1.0f));

	//第一個引數是紋理單元號， 第二個引數是紋理座標陣列
	geom->setTexCoordArray(0, vt.get());

	//設定法線  法線和光照有關
	osg::ref_ptr<osg::Vec3Array> nc = new osg::Vec3Array();
	nc->push_back(osg::Vec3(0.0f, -1.0f, 0.0f));

	geom->setNormalArray(nc.get());
	//法線繫結方式：用一條法線繫結所有的頂點
	geom->setNormalBinding(osg::Geometry::BIND_OVERALL);

	//新增圖元
	geom->addPrimitiveSet(new osg::DrawArrays(osg::PrimitiveSet::QUADS,0,4));

	//繪製
	geode->addDrawable(geom.get());

	return geode.get();
}

//建立二維紋理狀態物件
osg::ref_ptr<osg::StateSet> createTexture2DState(osg::ref_ptr<osg::Image> image)
{
	//建立狀態集物件
	osg::ref_ptr<osg::StateSet> stateset = new osg::StateSet();

	//建立二維紋理物件
	osg::ref_ptr<osg::Texture2D> texture = new osg::Texture2D();
	texture->setDataVariance(osg::Object::DYNAMIC);
	//設定貼圖
	texture->setImage(image.get());
	stateset->setTextureAttributeAndModes(0, texture.get(), osg::StateAttribute::ON);

	return stateset.get();
}


int main()
{
	osg::ref_ptr<osgViewer::Viewer> viewer = new osgViewer::Viewer();
	osg::ref_ptr<osg::Group> root = new osg::Group();

	//讀取貼圖檔案
	osg::ref_ptr<osg::Image> image = osgDB::readImageFile("Images/primitives.gif");
	osg::ref_ptr<osg::Node> node = createNode();

	//建立狀態集物件
	osg::ref_ptr<osg::StateSet> stateset = new osg::StateSet();
	stateset = createTexture2DState(image.get());

	//使用二維紋理
	node->setStateSet(stateset.get());

	root->addChild(node.get());

	//優化場景資料
	osgUtil::Optimizer optimizer;
	optimizer.optimize(root.get());

	//設定場景資料
	viewer->setSceneData(root.get());
	//初始化並建立視窗
	viewer->realize();
	//開始渲染
	viewer->run();

	return 0;
}