OSG 设置背景，前景

1。设置背景

 #include <osg/Group>
 #include <osgViewer/Viewer>
 #include <osgDB/ReadFile>
 #include <osg/Camera>
 #include <osg/Texture2D>
 #include <iostream>

 /*
 方法：
 HUD中的相机设置渲染顺序为PRE_RENDER,主相机清除深度缓存.
  */

 osg::Camera* createHUDBg(std::string imagePath){
   osg::ref_ptr<osg::Camera>camera=new osg::Camera;
   camera->setProjectionMatrixAsOrtho2D(0, 800, 0, 600);
   camera->setReferenceFrame(osg::Transform::ABSOLUTE_RF);
   camera->setRenderOrder(osg::Camera::PRE_RENDER);
   camera->setViewport(0,0,1300,800);
   camera->setClearMask(GL_DEPTH_BUFFER_BIT);
   camera->setAllowEventFocus(false);
   camera->setViewMatrix(osg::Matrix::identity());

   osg::ref_ptr<osg::Geode>geode=new osg::Geode;
   geode->getOrCreateStateSet()->setMode(GL_LIGHTING,osg::StateAttribute::OFF);

   osg::ref_ptr<osg::Geometry>gm=new osg::Geometry;

 //亚入顶点
   osg::ref_ptr<osg::Vec3Array>vertex=new osg::Vec3Array;
   vertex->push_back(osg::Vec3(0,0,0));
   vertex->push_back(osg::Vec3(800,0,0));
   vertex->push_back(osg::Vec3(800,600,0));
   vertex->push_back(osg::Vec3(0,600,0));
   gm->setVertexArray(vertex);

 //压入法线

 //纹理坐标
   osg::ref_ptr<osg::Vec2Array>coord=new osg::Vec2Array;
   coord->push_back(osg::Vec2(0,0));
   coord->push_back(osg::Vec2(1,0));
   coord->push_back(osg::Vec2(1,1));
   coord->push_back(osg::Vec2(0,1));
   gm->setTexCoordArray(0, coord);
   gm->addPrimitiveSet(new osg::DrawArrays(osg::PrimitiveSet::QUADS,0,4));

   osg::ref_ptr<osg::Image>image=osgDB::readImageFile(imagePath);
   if(!image.valid()){
 //    std::cout<"read image faild "<<std::endl;
     return camera.release();
   }
 //  osg::ref_ptr<osg::Texture2D>t2d=new osg::Texture2D;
   osg::Texture2D*t2d=new osg::Texture2D;
   t2d->setImage(0,image);


   gm->getOrCreateStateSet()->setTextureAttributeAndModes(0, t2d,osg::StateAttribute::ON);
   geode->addDrawable(gm);
   camera->addChild(geode);
   return camera.release();
 }

 int main(int argc, char *argv[])
 {
   osg::ref_ptr<osgViewer::Viewer>viewer=new osgViewer::Viewer;
   viewer->getCamera()->setClearMask(GL_DEPTH_BUFFER_BIT);
   osg::ref_ptr<osg::Group>root=new osg::Group;
   root->addChild(osgDB::readNodeFile("cow.osg"));
   root->addChild(createHUDBg("Images/skymap.jpg"));
   viewer->setSceneData(root.get());
   return viewer->run();
   }

这个不能随着屏幕的缩放而缩放，当然解决办法有很多

前景，挺玄的，呵呵

 #include <osg/Group>
 #include <osgViewer/Viewer>
 #include <osgDB/ReadFile>
 #include <osg/Camera>
 #include <osg/Texture2D>
 #include <iostream>

 /*
 前景方法：
 HUD中的相机设置渲染顺序为POST_RENDER,主相机不清除深度缓存.
  */

 osg::Camera* createHUDBg(std::string imagePath){
   osg::ref_ptr<osg::Camera>camera=new osg::Camera;
   camera->setProjectionMatrixAsOrtho2D(0, 800, 0, 600);
   camera->setReferenceFrame(osg::Transform::ABSOLUTE_RF);
   camera->setRenderOrder(osg::Camera::POST_RENDER);
   camera->setViewport(0,0,1300,800);
   camera->setClearMask(GL_DEPTH_BUFFER_BIT);
   camera->setAllowEventFocus(false);
   camera->setViewMatrix(osg::Matrix::identity());

   osg::ref_ptr<osg::Geode>geode=new osg::Geode;
   geode->getOrCreateStateSet()->setMode(GL_LIGHTING,osg::StateAttribute::OFF);
   geode->getOrCreateStateSet()->setMode(GL_BLEND,osg::StateAttribute::ON);

   osg::ref_ptr<osg::Geometry>gm=new osg::Geometry;

 //亚入顶点
   osg::ref_ptr<osg::Vec3Array>vertex=new osg::Vec3Array;
   vertex->push_back(osg::Vec3(0,0,0));
   vertex->push_back(osg::Vec3(800,0,0));
   vertex->push_back(osg::Vec3(800,600,0));
   vertex->push_back(osg::Vec3(0,600,0));
   gm->setVertexArray(vertex);

 //压入法线

 //纹理坐标
   osg::ref_ptr<osg::Vec2Array>coord=new osg::Vec2Array;
   coord->push_back(osg::Vec2(0,0));
   coord->push_back(osg::Vec2(1,0));
   coord->push_back(osg::Vec2(1,1));
   coord->push_back(osg::Vec2(0,1));
   gm->setTexCoordArray(0, coord);
   gm->addPrimitiveSet(new osg::DrawArrays(osg::PrimitiveSet::QUADS,0,4));

   osg::ref_ptr<osg::Image>image=osgDB::readImageFile(imagePath);
   if(!image.valid()){
 //    std::cout<"read image faild "<<std::endl;
     return camera.release();
   }
 //  osg::ref_ptr<osg::Texture2D>t2d=new osg::Texture2D;
   osg::Texture2D*t2d=new osg::Texture2D;
   t2d->setImage(0,image);


   gm->getOrCreateStateSet()->setTextureAttributeAndModes(0, t2d,osg::StateAttribute::ON);
   geode->addDrawable(gm);
   camera->addChild(geode);
   return camera.release();
 }

 int main(int argc, char *argv[])
 {
   osg::ref_ptr<osgViewer::Viewer>viewer=new osgViewer::Viewer;
 //  viewer->getCamera()->setClearMask(GL_DEPTH_BUFFER_BIT);
   osg::ref_ptr<osg::Group>root=new osg::Group;
   root->addChild(osgDB::readNodeFile("cow.osg"));
   root->addChild(createHUDBg("Images/smoke.rgb"));
   viewer->setSceneData(root.get());
   return viewer->run();
   }

 

 

OSG 背景设置 （摘自王锐的cookbook）

 #include <osg/Geometry>
 #include <osg/Geode>
 #include <osg/Depth>
 #include <osg/Texture2D>
 #include <osgDB/ReadFile>
 #include <osgViewer/Viewer>

 int main( int argc, char** argv )
 {
     osg::ref_ptr<osg::Texture2D> texture = new osg::Texture2D;
     osg::ref_ptr<osg::Image> image = osgDB::readImageFile( "D:/background1.png" );
     texture->setImage( image.get() );

     osg::ref_ptr<osg::Drawable> quad = osg::createTexturedQuadGeometry(osg::Vec3(), osg::Vec3(1.0f, 0.0f, 0.0f), osg::Vec3(0.0f, 1.0f, 0.0f) );
     quad->getOrCreateStateSet()->setTextureAttributeAndModes( 0,texture.get());

     osg::ref_ptr<osg::Geode> geode = new osg::Geode;
     geode->addDrawable( quad.get() );

     osg::ref_ptr<osg::Camera> camera = new osg::Camera;
     camera->setClearMask( 0 );
     camera->setCullingActive( false );
     camera->setAllowEventFocus( false );
     camera->setReferenceFrame( osg::Transform::ABSOLUTE_RF );
     camera->setRenderOrder( osg::Camera::POST_RENDER );
     camera->setProjectionMatrix( osg::Matrix::ortho2D(0.0, 1.0, 0.0, 1.0) );
     camera->addChild( geode.get() );

     osg::StateSet* ss = camera->getOrCreateStateSet();
     ss->setMode( GL_LIGHTING, osg::StateAttribute::OFF );
     ss->setAttributeAndModes( new osg::Depth(osg::Depth::LEQUAL, 1.0, 1.0) );

     osg::ref_ptr<osg::Group> root = new osg::Group;
     root->addChild( camera.get() );
     root->addChild( osgDB::readNodeFile("cessna.osg") );

     osgViewer::Viewer viewer;
     viewer.setSceneData( root.get() );
     return viewer.run();
 }

 

上面的关键地方 就在

setAttributeAndModes( new osg::Depth(osg::Depth::LEQUAL,1.0, 1.0) ); 这句话，

重新映射背景节点的深度值为1-1 ，这样就确保了每个后渲染(post-rendered)背景的深度值是1，osg::Depth::LEQUAL 确保除非原始深度缓存的值为1才会渲染上背景，否则此地方背景不会被渲染。

那么什么时候，原始缓存的深度值为1 ？ 答案是：深度缓存在初始化的时候都是1，当有像素绘制后，此像素对应的深度缓存就不为1，也就是说所有没有被渲染的地方都是1. 这样没被渲染的地方，在post-rendered 的时候就渲染了背景色。确保原有模型像素点不被覆盖。