OpenSceneGraph基础:光照

最新推荐文章于 2023-12-31 10:17:07 发布
原创 最新推荐文章于 2023-12-31 10:17:07 发布 · 5.7k 阅读 · 3 ·
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本文是OpenSceneGraph系列的续篇，重点介绍如何在场景中添加光照效果。主要内容包括窗口初始化、场景初始化，特别是如何创建材质属性、设置光源，并通过更新函数让光源动态运动。通过学习，读者将掌握在OpenSceneGraph中实现基本光照的方法。

效果：

接着前篇进行（http://blog.youkuaiyun.com/boksic/article/details/44002155），现在考虑光照效果

主程序

转载请注明http://blog.youkuaiyun.com/boksic 如有疑问欢迎留言

和之前基本唯一的变化就是把窗口部分的操作放在初始化函数initCanvas里进行。

int main(int argc, const char* argv[]) {

	
	osg::Group *scene = startupScene();

	osg::ref_ptr<osgViewer::Viewer> viewer = new osgViewer::Viewer;
	viewer->setSceneData(scene);	
	initCanvas(viewer);

	while (!viewer->done()) {
		viewer->frame();
		update(0.5); // do the update advancing 500ms
	}
	return 0;
}

窗口初始化(initCanvas)

我们使用GraphicsContext类来对设备上下文进行操作，该类需要一个Traits结构来定义具体的窗口属性，例如窗口大小，窗口位置等。

void initCanvas(osg::ref_ptr<osgViewer::Viewer> viewer) {
	int x = 20;
	int y = 20;
	osg::ref_ptr<osg::GraphicsContext::Traits> traits = new osg::GraphicsContext::Traits;
	traits->x = x;
	traits->y = y;
	traits->width = width;
	traits->height = height;
	if (offScreen) {
		traits->windowDecoration = false;
		traits->doubleBuffer = true;
		traits->pbuffer = true;
	}
	else {
		traits->windowDecoration = true;
		traits->doubleBuffer = true;
		traits->pbuffer = false;
	}
	traits->windowName = "http://blog.youkuaiyun.com/boksic";
	traits->sharedContext = 0;
	traits->alpha = 8;
	traits->readDISPLAY();
	traits->setUndefinedScreenDetailsToDefaultScreen();

	osg::GraphicsContext* _gc = osg::GraphicsContext::createGraphicsContext(traits.get());

	if (!_gc) {
		osg::notify(osg::NOTICE)
			<< "Failed to create pbuffer, failing back to normal graphics window." << endl;

		traits->pbuffer = false;
		_gc = osg::GraphicsContext::createGraphicsContext(traits.get());
	}

}

Viewer内置了Camera对象来控制窗口，我们可以通过getCamera函数来对该对象进行操作，例如setClearColor设置清屏颜色。

	viewer->getCamera()->setGraphicsContext(_gc);
	viewer->getCamera()->setViewport(new osg::Viewport(x, y, width, height));
	viewer->getCamera()->setClearColor(osg::Vec4(0, 0, 0, 1));


	viewer->setCameraManipulator(new osgGA::TrackballManipulator);
	viewer->setThreadingModel(osgViewer::ViewerBase::SingleThreaded);
	viewer->realize();
	viewer->setReleaseContextAtEndOfFrameHint(false);



场景初始化（startup）

首先按前篇的方法建立几何图形：

	//球
	osg::Geode *sphere = new osg::Geode();
	sphere->addDrawable(new osg::ShapeDrawable(new osg::Sphere(osg::Vec3(-2, 0, 0), 1)));
	//正方体
	osg::Geode *cube = createCube();
	cubeTransform = new osg::PositionAttitudeTransform();
	cubeTransform->addChild(cube);
	cubeTransform->setPosition(osg::Vec3(2, 0, -1));
	//金字塔
	osg::Geode *pyramid = createPyramid();
	pyramidTransform = new osg::PositionAttitudeTransform();
	pyramidTransform->addChild(pyramid);
	pyramidTransform->setPosition(osg::Vec3(5, 0, -1));
这里，球是按照osg内置函数建立模型，金子塔与之前相同，正方体则使用了setNormalBinding来绑定法向量用到了法向量（注意：与颜色索引一样，设置法线索引的setNormalIndices也已经被废除了），正方体的建立函数：
osg::Geode *createCube() {
	// vertex array
	osg::Vec3Array *vertexArray = new osg::Vec3Array();

	// bottom front left
	vertexArray->push_back(osg::Vec3(-1, -1, 0));
	vertexArray->push_back(osg::Vec3(-1, -1, 0));
	vertexArray->push_back(osg::Vec3(-1, -1, 0));
	// bottom front right
	vertexArray->push_back(osg::Vec3(+1, -1, 0));
	vertexArray->push_back(osg::Vec3(+1, -1, 0));
	vertexArray->push_back(osg::Vec3(+1, -1, 0));
	// bottom back right
	vertexArray->push_back(osg::Vec3(+1, +1, 0));
	vertexArray->push_back(osg::Vec3(+1, +1, 0));
	vertexArray->push_back(osg::Vec3(+1, +1, 0));
	// bottom back left
	vertexArray->push_back(osg::Vec3(-1, +1, 0));
	vertexArray->push_back(osg::Vec3(-1, +1, 0));
	vertexArray->push_back(osg::Vec3(-1, +1, 0));

	// top front left
	vertexArray->push_back(osg::Vec3(-1, -1, 2));
	vertexArray->push_back(osg::Vec3(-1, -1, 2));
	vertexArray->push_back(osg::Vec3(-1, -1, 2));
	// top front right
	vertexArray->push_back(osg::Vec3(+1, -1, 2));
	vertexArray->push_back(osg::Vec3(+1, -1, 2));
	vertexArray->push_back(osg::Vec3(+1, -1, 2));
	// top back right
	vertexArray->push_back(osg::Vec3(+1, +1, 2));
	vertexArray->push_back(osg::Vec3(+1, +1, 2));
	vertexArray->push_back(osg::Vec3(+1, +1, 2));
	// top back left
	vertexArray->push_back(osg::Vec3(-1, +1, 2));
	vertexArray->push_back(osg::Vec3(-1, +1, 2));
	vertexArray->push_back(osg::Vec3(-1, +1, 2));


	// face array
	osg::DrawElementsUInt *faceArray = new osg::DrawElementsUInt(osg::PrimitiveSet::TRIANGLES, 0);

	// bottom
	faceArray->push_back(0); // face 1
	faceArray->push_back(9);
	faceArray->push_back(3);
	faceArray->push_back(9); // face 2
	faceArray->push_back(6);
	faceArray->push_back(3);
	// top
	faceArray->push_back(21);  //face 3
	faceArray->push_back(12);
	faceArray->push_back(18);
	faceArray->push_back(12);  //face 4
	faceArray->push_back(15);
	faceArray->push_back(18);
	// left
	faceArray->push_back(22);  //face 5
	faceArray->push_back(10);
	faceArray->push_back(13);
	faceArray->push_back(10);  //face 6
	faceArray->push_back(1);
	faceArray->push_back(13);
	// right
	faceArray->push_back(16);  //face 7
	faceArray->push_back(4);
	faceArray->push_back(19);
	faceArray->push_back(4);  //face 8
	faceArray->push_back(7);
	faceArray->push_back(19);
	// front
	faceArray->push_back(14);  //face 9
	faceArray->push_back(2);
	faceArray->push_back(17);
	faceArray->push_back(2);   //face 10
	faceArray->push_back(5);
	faceArray->push_back(17);
	// back
	faceArray->push_back(20);  //face 11
	faceArray->push_back(8);
	faceArray->push_back(23);
	faceArray->push_back(8);   //face 12
	faceArray->push_back(11);
	faceArray->push_back(23);

	// normal array
	osg::Vec3Array *normalArray = new osg::Vec3Array();
	normalArray->push_back(osg::Vec3(0, 0, -1));
	normalArray->push_back(osg::Vec3(0, -1, 0));
	normalArray->push_back(osg::Vec3(+1, 0, 0));

	normalArray->push_back(osg::Vec3(0, 0, -1));
	normalArray->push_back(osg::Vec3(0, +1, 0));
	normalArray->push_back(osg::Vec3(+1, 0, 0));

	normalArray->push_back(osg::Vec3(0, 0, -1));
	normalArray->push_back(osg::Vec3(0, +1, 0));
	normalArray->push_back(osg::Vec3(-1, 0, 0));

	normalArray->push_back(osg::Vec3(0, 0, -1));
	normalArray->push_back(osg::Vec3(0, -1, 0));
	normalArray->push_back(osg::Vec3(-1, 0, 0));

	normalArray->push_back(osg::Vec3(0, 0, +1));
	normalArray->push_back(osg::Vec3(0, -1, 0));
	normalArray->push_back(osg::Vec3(+1, 0, 0));

	normalArray->push_back(osg::Vec3(0, 0, +1));
	normalArray->push_back(osg::Vec3(0, +1, 0));
	normalArray->push_back(osg::Vec3(+1, 0, 0));

	normalArray->push_back(osg::Vec3(0, 0, +1));
	normalArray->push_back(osg::Vec3(0, +1, 0));
	normalArray->push_back(osg::Vec3(-1, 0, 0));

	normalArray->push_back(osg::Vec3(0, 0, +1));
	normalArray->push_back(osg::Vec3(0, -1, 0));
	normalArray->push_back(osg::Vec3(-1, 0, 0));

	osg::Geometry *geometry = new osg::Geometry();
	geometry->setVertexArray(vertexArray);

	geometry->setNormalArray(normalArray);
	geometry->setNormalBinding(osg::Geometry::BIND_PER_VERTEX);
	geometry->addPrimitiveSet(faceArray);

	osg::Geode *cube = new osg::Geode();
	cube->addDrawable(geometry);
	return cube;
}


建立组节点，获取其渲染状态StateSet。StateSet保存了一系列Opengl的渲染属性和值，用于控制节点下图形的渲染，若要设置则需获取该对象的StateSet后进行操作。

StateSet *lightStateSet;
Node *startup() { 
        Group *scene = new Group();
	lightStateSet = scene->getOrCreateStateSet();
}

建立材质属性

osg的Material 封装了OpenGL 的glMaterial()和glColorMaterial()，用法基本类似。而建立Material后再关联到图形的StateSet中即可试目标图形具有该材质属性。这里为球体和正方体赋予了该材质。

	// create white material
	osg::Material *material = new osg::Material();
	material->setDiffuse(osg::Material::FRONT, osg::Vec4(1.0, 1.0, 1.0, 1.0));
	material->setSpecular(osg::Material::FRONT, osg::Vec4(0.0, 0.0, 0.0, 1.0));
	material->setAmbient(osg::Material::FRONT, osg::Vec4(0.1, 0.1, 0.1, 1.0));
	material->setEmission(osg::Material::FRONT, osg::Vec4(0.0, 0.0, 0.0, 1.0));
	material->setShininess(osg::Material::FRONT, 25.0);

	// assign the material to the sphere and cube
	sphere->getOrCreateStateSet()->setAttribute(material);
	cube->getOrCreateStateSet()->setAttribute(material);

设置光源

OSG使用Light对象来定义光源属性，Light的setLightNum函数是用来关联OpenGL的位置数GL_LIGHT0 到GL_LIGHT7的，所以需要赋予其一个唯一的值（uniqueLightNumber）。我们可以定义一个简单的光源生成函数

int uniqueLightNumber = 0;
osg::Light *createLight(osg::Vec4 color)
{
	osg::Light *light = new osg::Light();
	// each light must have a unique number
	light->setLightNum(uniqueLightNumber++);
	// we set the light's position via a PositionAttitudeTransform object
	light->setPosition(osg::Vec4(0.0, 0.0, 0.0, 1.0));
	light->setDiffuse(color);
	light->setSpecular(osg::Vec4(1.0, 1.0, 1.0, 1.0));
	light->setAmbient(osg::Vec4(0.0, 0.0, 0.0, 1.0));

	return light;
}

而Light对象需要放在LightSource的节点当中,可以通过LightSource来控制灯光的位置以及状态。 

	// Create Lights - Red, Green, Blue
	osg::Vec4 lightColors[] = { osg::Vec4(1.0, 0.0, 0.0, 1.0), osg::Vec4(0.0, 1.0, 0.0, 1.0), osg::Vec4(0.0, 0.0, 1.0, 1.0) };

	osg::Group *root = new osg::Group();
	lightStateSet = root->getOrCreateStateSet();

	osg::Geode *lightMarker[LIGHTS];
	osg::LightSource *lightSource[LIGHTS];


	for (int i = 0; i < LIGHTS; i++) {
		lightMarker[i] = new osg::Geode();
		lightMarker[i]->addDrawable(new osg::ShapeDrawable(new osg::Sphere(osg::Vec3(), 1)));
		lightMarker[i]->getOrCreateStateSet()->setAttribute(createSimpleMaterial(lightColors[i]));

		lightSource[i] = new osg::LightSource();
		lightSource[i]->setLight(createLight(lightColors[i]));
		lightSource[i]->setLocalStateSetModes(osg::StateAttribute::ON);
		lightSource[i]->setStateSetModes(*lightStateSet, osg::StateAttribute::ON);

		lightTransform[i] = new osg::PositionAttitudeTransform();
		lightTransform[i]->addChild(lightSource[i]);
		lightTransform[i]->addChild(lightMarker[i]);
		lightTransform[i]->setPosition(osg::Vec3(0, 0, 5));
		lightTransform[i]->setScale(osg::Vec3(0.1, 0.1, 0.1));

		root->addChild(lightTransform[i]);
	}

最后不忘添加到组节点当中 

		root->addChild(sphere);
		root->addChild(cubeTransform);
		root->addChild(pyramidTransform);

更新部分（update函数）

这里实现的是三个点光源做圆周运动

void update(float dt) {
	myTimer += 0.01*dt;
	lightTransform[0]->setPosition(osg::Vec3(cos(myTimer), sin(myTimer), 0) * 4);
	lightTransform[1]->setPosition(osg::Vec3(0, cos(myTimer), sin(myTimer)) * 4);
	lightTransform[2]->setPosition(osg::Vec3(sin(myTimer), cos(myTimer), sin(myTimer)) * 4);
}





最后附上完整代码


#include <osgGA/TrackballManipulator> 
#include <osg/PositionAttitudeTransform>
#include <osgGA/GUIEventHandler>
#include <osg/Material>
#include <osg/ShapeDrawable>
osg::Geode *createCube() {
	// vertex array
	osg::Vec3Array *vertexArray = new osg::Vec3Array();

	// bottom front left
	vertexArray->push_back(osg::Vec3(-1, -1, 0));
	vertexArray->push_back(osg::Vec3(-1, -1, 0));
	vertexArray->push_back(osg::Vec3(-1, -1, 0));
	// bottom front right
	vertexArray->push_back(osg::Vec3(+1, -1, 0));
	vertexArray->push_back(osg::Vec3(+1, -1, 0));
	vertexArray->push_back(osg::Vec3(+1, -1, 0));
	// bottom back right
	vertexArray->push_back(osg::Vec3(+1, +1, 0));
	vertexArray->push_back(osg::Vec3(+1, +1, 0));
	vertexArray->push_back(osg::Vec3(+1, +1, 0));
	// bottom back left
	vertexArray->push_back(osg::Vec3(-1, +1, 0));
	vertexArray->push_back(osg::Vec3(-1, +1, 0));
	vertexArray->push_back(osg::Vec3(-1, +1, 0));

	// top front left
	vertexArray->push_back(osg::Vec3(-1, -1, 2));
	vertexArray->push_back(osg::Vec3(-1, -1, 2));
	vertexArray->push_back(osg::Vec3(-1, -1, 2));
	// top front right
	vertexArray->push_back(osg::Vec3(+1, -1, 2));
	vertexArray->push_back(osg::Vec3(+1, -1, 2));
	vertexArray->push_back(osg::Vec3(+1, -1, 2));
	// top back right
	vertexArray->push_back(osg::Vec3(+1, +1, 2));
	vertexArray->push_back(osg::Vec3(+1, +1, 2));
	vertexArray->push_back(osg::Vec3(+1, +1, 2));
	// top back left
	vertexArray->push_back(osg::Vec3(-1, +1, 2));
	vertexArray->push_back(osg::Vec3(-1, +1, 2));
	vertexArray->push_back(osg::Vec3(-1, +1, 2));


	// face array
	osg::DrawElementsUInt *faceArray = new osg::DrawElementsUInt(osg::PrimitiveSet::TRIANGLES, 0);

	// bottom
	faceArray->push_back(0); // face 1
	faceArray->push_back(9);
	faceArray->push_back(3);
	faceArray->push_back(9); // face 2
	faceArray->push_back(6);
	faceArray->push_back(3);
	// top
	faceArray->push_back(21);  //face 3
	faceArray->push_back(12);
	faceArray->push_back(18);
	faceArray->push_back(12);  //face 4
	faceArray->push_back(15);
	faceArray->push_back(18);
	// left
	faceArray->push_back(22);  //face 5
	faceArray->push_back(10);
	faceArray->push_back(13);
	faceArray->push_back(10);  //face 6
	faceArray->push_back(1);
	faceArray->push_back(13);
	// right
	faceArray->push_back(16);  //face 7
	faceArray->push_back(4);
	faceArray->push_back(19);
	faceArray->push_back(4);  //face 8
	faceArray->push_back(7);
	faceArray->push_back(19);
	// front
	faceArray->push_back(14);  //face 9
	faceArray->push_back(2);
	faceArray->push_back(17);
	faceArray->push_back(2);   //face 10
	faceArray->push_back(5);
	faceArray->push_back(17);
	// back
	faceArray->push_back(20);  //face 11
	faceArray->push_back(8);
	faceArray->push_back(23);
	faceArray->push_back(8);   //face 12
	faceArray->push_back(11);
	faceArray->push_back(23);

	// normal array
	osg::Vec3Array *normalArray = new osg::Vec3Array();
	normalArray->push_back(osg::Vec3(0, 0, -1));
	normalArray->push_back(osg::Vec3(0, -1, 0));
	normalArray->push_back(osg::Vec3(+1, 0, 0));

	normalArray->push_back(osg::Vec3(0, 0, -1));
	normalArray->push_back(osg::Vec3(0, +1, 0));
	normalArray->push_back(osg::Vec3(+1, 0, 0));

	normalArray->push_back(osg::Vec3(0, 0, -1));
	normalArray->push_back(osg::Vec3(0, +1, 0));
	normalArray->push_back(osg::Vec3(-1, 0, 0));

	normalArray->push_back(osg::Vec3(0, 0, -1));
	normalArray->push_back(osg::Vec3(0, -1, 0));
	normalArray->push_back(osg::Vec3(-1, 0, 0));

	normalArray->push_back(osg::Vec3(0, 0, +1));
	normalArray->push_back(osg::Vec3(0, -1, 0));
	normalArray->push_back(osg::Vec3(+1, 0, 0));

	normalArray->push_back(osg::Vec3(0, 0, +1));
	normalArray->push_back(osg::Vec3(0, +1, 0));
	normalArray->push_back(osg::Vec3(+1, 0, 0));

	normalArray->push_back(osg::Vec3(0, 0, +1));
	normalArray->push_back(osg::Vec3(0, +1, 0));
	normalArray->push_back(osg::Vec3(-1, 0, 0));

	normalArray->push_back(osg::Vec3(0, 0, +1));
	normalArray->push_back(osg::Vec3(0, -1, 0));
	normalArray->push_back(osg::Vec3(-1, 0, 0));

	osg::Geometry *geometry = new osg::Geometry();
	geometry->setVertexArray(vertexArray);

	geometry->setNormalArray(normalArray);
	geometry->setNormalBinding(osg::Geometry::BIND_PER_VERTEX);
	geometry->addPrimitiveSet(faceArray);

	osg::Geode *cube = new osg::Geode();
	cube->addDrawable(geometry);
	return cube;
}

osg::Geode *createPyramid(){
	// vertex array
	osg::Vec3Array *vertexArray = new osg::Vec3Array();
	vertexArray->push_back(osg::Vec3(-1, -1, 0)); // front left 
	vertexArray->push_back(osg::Vec3(+1, -1, 0)); // front right 
	vertexArray->push_back(osg::Vec3(+1, +1, 0)); // back right 
	vertexArray->push_back(osg::Vec3(-1, +1, 0)); // back left 
	vertexArray->push_back(osg::Vec3(0,0 ,  sqrt(2))); // peak
	vertexArray->push_back(osg::Vec3(0, 0, -sqrt(2))); // lower peak

	// face array
	// give indices of vertices in counter-clockwise order
	osg::DrawElementsUInt *faceArray = new osg::DrawElementsUInt(osg::PrimitiveSet::TRIANGLES, 0);
	faceArray->push_back(0); // face 0
	faceArray->push_back(1);
	faceArray->push_back(4);
	faceArray->push_back(1); // face 1
	faceArray->push_back(2);
	faceArray->push_back(4);
	faceArray->push_back(2); // face 2
	faceArray->push_back(3);
	faceArray->push_back(4);
	faceArray->push_back(3); // face 3
	faceArray->push_back(0);
	faceArray->push_back(4);
	faceArray->push_back(0); // face 4
	faceArray->push_back(5);
	faceArray->push_back(1);
	faceArray->push_back(2); // face 5
	faceArray->push_back(1);
	faceArray->push_back(5);
	faceArray->push_back(3); // face 6
	faceArray->push_back(2);
	faceArray->push_back(5);
	faceArray->push_back(0); // face 7
	faceArray->push_back(3);
	faceArray->push_back(5);

	// vertex color array
	osg::Vec4Array *colorArray = new osg::Vec4Array();
	colorArray->push_back(osg::Vec4(1.0f, 0.0f, 0.0f, 1.0f)); //index 0 red
	colorArray->push_back(osg::Vec4(0.0f, 1.0f, 0.0f, 1.0f)); //index 1 green
	colorArray->push_back(osg::Vec4(0.0f, 0.0f, 1.0f, 1.0f)); //index 2 blue
	colorArray->push_back(osg::Vec4(1.0f, 0.0f, 1.0f, 1.0f)); //index 3 purple
	colorArray->push_back(osg::Vec4(1.0f, 1.0f, 0.0f, 1.0f)); //index 4 white
	colorArray->push_back(osg::Vec4(1.0f, 1.0f, 0.5f, 1.0f)); //index 5 white


	osg::Geometry *geometry = new osg::Geometry();
	geometry->setVertexArray(vertexArray);
	geometry->setColorArray(colorArray);
	geometry->setColorBinding(osg::Geometry::BIND_PER_VERTEX);
	geometry->addPrimitiveSet(faceArray);

	osg::Geode *pyramid = new osg::Geode();
	pyramid->addDrawable(geometry);
	return pyramid;
}


int uniqueLightNumber = 0;
osg::Light *createLight(osg::Vec4 color)
{
	osg::Light *light = new osg::Light();
	// each light must have a unique number
	light->setLightNum(uniqueLightNumber++);
	// we set the light's position via a PositionAttitudeTransform object
	light->setPosition(osg::Vec4(0.0, 0.0, 0.0, 1.0));
	light->setDiffuse(color);
	light->setSpecular(osg::Vec4(1.0, 1.0, 1.0, 1.0));
	light->setAmbient(osg::Vec4(0.0, 0.0, 0.0, 1.0));

	return light;
}
osg::Material *createSimpleMaterial(osg::Vec4 color)
{
	osg::Material *material = new osg::Material();
	material->setDiffuse(osg::Material::FRONT, osg::Vec4(0.0, 0.0, 0.0, 1.0));
	material->setEmission(osg::Material::FRONT, color);

	return material;
}

int const LIGHTS = 3;
osg::PositionAttitudeTransform *cubeTransform;
osg::PositionAttitudeTransform *pyramidTransform;
osg::PositionAttitudeTransform *lightTransform[LIGHTS]; 
osg::StateSet *lightStateSet;
osg::Group * startupScene()
{
	//球
	osg::Geode *sphere = new osg::Geode();
	sphere->addDrawable(new osg::ShapeDrawable(new osg::Sphere(osg::Vec3(-2, 0, 0), 1)));
	//正方体
	osg::Geode *cube = createCube();
	cubeTransform = new osg::PositionAttitudeTransform();
	cubeTransform->addChild(cube);
	cubeTransform->setPosition(osg::Vec3(2, 0, -1));
	//金字塔
	osg::Geode *pyramid = createPyramid();
	pyramidTransform = new osg::PositionAttitudeTransform();
	pyramidTransform->addChild(pyramid);
	pyramidTransform->setPosition(osg::Vec3(5, 0, -1));


	// create white material
	osg::Material *material = new osg::Material();
	material->setDiffuse(osg::Material::FRONT, osg::Vec4(1.0, 1.0, 1.0, 1.0));
	material->setSpecular(osg::Material::FRONT, osg::Vec4(0.0, 0.0, 0.0, 1.0));
	material->setAmbient(osg::Material::FRONT, osg::Vec4(0.1, 0.1, 0.1, 1.0));
	material->setEmission(osg::Material::FRONT, osg::Vec4(0.0, 0.0, 0.0, 1.0));
	material->setShininess(osg::Material::FRONT, 25.0);

	// assign the material to the sphere and cube
	sphere->getOrCreateStateSet()->setAttribute(material);
	cube->getOrCreateStateSet()->setAttribute(material);

	// Create Lights - Red, Green, Blue
	osg::Vec4 lightColors[] = { osg::Vec4(1.0, 0.0, 0.0, 1.0), osg::Vec4(0.0, 1.0, 0.0, 1.0), osg::Vec4(0.0, 0.0, 1.0, 1.0) };

	osg::Group *root = new osg::Group();
	lightStateSet = root->getOrCreateStateSet();

	osg::Geode *lightMarker[LIGHTS];
	osg::LightSource *lightSource[LIGHTS];


	for (int i = 0; i < LIGHTS; i++) {
		lightMarker[i] = new osg::Geode();
		lightMarker[i]->addDrawable(new osg::ShapeDrawable(new osg::Sphere(osg::Vec3(), 1)));
		lightMarker[i]->getOrCreateStateSet()->setAttribute(createSimpleMaterial(lightColors[i]));

		lightSource[i] = new osg::LightSource();
		lightSource[i]->setLight(createLight(lightColors[i]));
		lightSource[i]->setLocalStateSetModes(osg::StateAttribute::ON);
		lightSource[i]->setStateSetModes(*lightStateSet, osg::StateAttribute::ON);

		lightTransform[i] = new osg::PositionAttitudeTransform();
		lightTransform[i]->addChild(lightSource[i]);
		lightTransform[i]->addChild(lightMarker[i]);
		lightTransform[i]->setPosition(osg::Vec3(0, 0, 5));
		lightTransform[i]->setScale(osg::Vec3(0.1, 0.1, 0.1));

		root->addChild(lightTransform[i]);
	}

		root->addChild(sphere);
		root->addChild(cubeTransform);
		root->addChild(pyramidTransform);
		return root;
}

float myTimer = 0;
void update(float dt) {
	myTimer += 0.01*dt;
	lightTransform[0]->setPosition(osg::Vec3(cos(myTimer), sin(myTimer), 0) * 4);
	lightTransform[1]->setPosition(osg::Vec3(0, cos(myTimer), sin(myTimer)) * 4);
	lightTransform[2]->setPosition(osg::Vec3(sin(myTimer), cos(myTimer), sin(myTimer)) * 4);
} 

const bool offScreen = false;
const int width = 640;
const int height = 480; ;
void initCanvas(osg::ref_ptr<osgViewer::Viewer> viewer) {
	int x = 20;
	int y = 20;
	osg::ref_ptr<osg::GraphicsContext::Traits> traits = new osg::GraphicsContext::Traits;
	traits->x = x;
	traits->y = y;
	traits->width = width;
	traits->height = height;
	if (offScreen) {
		traits->windowDecoration = false;
		traits->doubleBuffer = true;
		traits->pbuffer = true;
	}
	else {
		traits->windowDecoration = true;
		traits->doubleBuffer = true;
		traits->pbuffer = false;
	}
	traits->windowName = "http://blog.youkuaiyun.com/boksic";
	traits->sharedContext = 0;
	traits->alpha = 8;
	traits->readDISPLAY();
	traits->setUndefinedScreenDetailsToDefaultScreen();

	osg::GraphicsContext* _gc = osg::GraphicsContext::createGraphicsContext(traits.get());

	if (!_gc) {
		osg::notify(osg::NOTICE)
			<< "Failed to create pbuffer, failing back to normal graphics window." << endl;

		traits->pbuffer = false;
		_gc = osg::GraphicsContext::createGraphicsContext(traits.get());
	}
	viewer->getCamera()->setGraphicsContext(_gc);
	viewer->getCamera()->setViewport(new osg::Viewport(x, y, width, height));
	viewer->getCamera()->setClearColor(osg::Vec4(0, 0, 0, 1));


	viewer->setCameraManipulator(new osgGA::TrackballManipulator);
	viewer->setThreadingModel(osgViewer::ViewerBase::SingleThreaded);
	viewer->realize();
	viewer->setReleaseContextAtEndOfFrameHint(false);
}

int main(int argc, const char* argv[]) {	
	osg::Group *scene = startupScene();

	osg::ref_ptr<osgViewer::Viewer> viewer = new osgViewer::Viewer;
	viewer->setSceneData(scene);	
	initCanvas(viewer);

	while (!viewer->done()) {
		viewer->frame();
		update(0.5); // do the update advancing 500ms
	}
	return 0;
}


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