前言

osgearth_pick示例，展示了鼠标移动(或者鼠标单击)时，触及到的矢量特征、绘制的线、遮盖图等内容，会将这些内容的信息打印输出到屏幕上。

执行命令

// 三维地图或者二维地图都可。// 三维图
osgearth_pickd.exe earth_image\china-simple.earth// 二维图
osgearth_pickd.exe earth_image\world_projected.earth

效果

鼠标移动到某条线上(线条会变色)，获取到特征边界线的信息，显示在左上角。左下角显示矢量图。

鼠标移动到遮盖图上（或者线条上，线条会变色），获取遮盖图信息，现实在左上角下。左下角显示图元信息。

代码分析

本节示例，代码逻辑比前几篇更难理解一些。

#include <osgEarth/Registry>
#include <osgEarth/ShaderGenerator>
#include <osgEarth/ObjectIndex>
#include <osgEarth/GLUtils>
#include <osgEarthUtil/EarthManipulator>
#include <osgEarthUtil/ExampleResources>
#include <osgEarthUtil/Controls>
#include <osgEarthUtil/RTTPicker>
#include <osgEarthFeatures/Feature>
#include <osgEarthFeatures/FeatureIndex>
#include <osgEarthAnnotation/AnnotationNode>#include <osgEarth/IntersectionPicker>#include <osgViewer/CompositeViewer>
#include <osgGA/TrackballManipulator>
#include <osg/BlendFunc>#define LC "[rttpicker] "using namespace osgEarth;
using namespace osgEarth::Util;
using namespace osgEarth::Features;
using namespace osgEarth::Annotation;namespace ui = osgEarth::Util::Controls;//-----------------------------------------------------------------------//! Application-wide data.
struct App
{App(osg::ArgumentParser& args) : viewer(args), mainView(NULL), rttView(NULL), mapNode(NULL), picker(NULL) { }// 多视景器，且通过args初始化viewerosgViewer::CompositeViewer viewer;osgViewer::View* mainView;// 主视景器osgViewer::View* rttView; // rtt视景器osgEarth::MapNode* mapNode;osgEarth::Util::RTTPicker* picker;// rtt拾取类ui::LabelControl* fidLabel;ui::LabelControl* nameLabel;osg::Uniform*     highlightUniform;// 高亮的变量
};//! Callback that you install on the RTTPicker.
// 安装RTTPicker后，提供RTTPicker的回调方法
struct MyPickCallback : public RTTPicker::Callback
{App& _app;MyPickCallback(App& app) : _app(app) { }void onHit(ObjectID id){// First see whether it's a feature:FeatureIndex* index = Registry::objectIndex()->get<FeatureIndex>(id).get();Feature* feature = index ? index->getFeature( id ) : 0L;// 有feature标签，则拾取feature标签if ( feature ){_app.fidLabel->setText( Stringify() << "Feature ID = " << feature->getFID() << " (oid = " << id << ")" );_app.nameLabel->setText( Stringify() << "Name = " << feature->getString("name") );}else // 存在annotation标注，则拾取annotation标注{// Check whether it's an annotation:AnnotationNode* anno = Registry::objectIndex()->get<AnnotationNode>(id).get();if ( anno ){_app.fidLabel->setText( Stringify() << "ObjectID = " << id );_app.nameLabel->setName( Stringify() << "Name = " << anno->getName() );}// None of the above.. clear. 什么也没有获取到else{_app.fidLabel->setText( Stringify() << "unknown oid = " << id );_app.nameLabel->setText( " " );}}_app.highlightUniform->set( id );// 将对象id设置给高亮变量}// 取消拾取时，回复标签显示void onMiss(){_app.fidLabel->setText( "No pick." );_app.nameLabel->setText( " " );_app.highlightUniform->set( 0u );}// pick whenever the mouse moves.// 当鼠标移动时，获取。也可以改为鼠标点击时获取bool accept(const osgGA::GUIEventAdapter& ea, const osgGA::GUIActionAdapter& aa){// return ea.getEventType() == ea.MOVE;// 移动时获取，移动到空白区域，则取消选中和高亮。return ea.getEventType() == ea.RELEASE;// 点击时获取，再点击其他地方，则取消选中和高亮。}
};//-----------------------------------------------------------------------// Shaders that will highlight the currently "picked" feature.
// 顶点着色器和片段着色器
const char* highlightVert ="#version " GLSL_VERSION_STR "\n""uniform uint objectid_to_highlight; \n""uint oe_index_objectid;      // Stage global containing object id \n""flat out int selected; \n""void checkForHighlight(inout vec4 vertex) \n""{ \n""    selected = (objectid_to_highlight > 1u && objectid_to_highlight == oe_index_objectid) ? 1 : 0; \n""} \n";const char* highlightFrag ="#version " GLSL_VERSION_STR "\n""flat in int selected; \n""void highlightFragment(inout vec4 color) \n""{ \n""    if ( selected == 1 ) \n""        color.rgb = mix(color.rgb, clamp(vec3(0.5,2.0,2.0)*(1.0-color.rgb), 0.0, 1.0), 0.5); \n""} \n";// 安装高亮器到app
void installHighlighter(App& app)
{osg::StateSet* stateSet = app.mapNode->getOrCreateStateSet();// 索引geoemtry时要使用的顶点属性绑定位置。int attrLocation = Registry::objectIndex()->getObjectIDAttribLocation();// This shader program will highlight the selected object.// 着色器程序会使选中的object高亮VirtualProgram* vp = VirtualProgram::getOrCreate(stateSet);vp->setFunction( "checkForHighlight",  highlightVert, ShaderComp::LOCATION_VERTEX_CLIP );vp->setFunction( "highlightFragment",  highlightFrag, ShaderComp::LOCATION_FRAGMENT_COLORING );// Since we're accessing object IDs, we need to load the indexing shader as well:// 由于我们正在访问对象ID，因此还需要加载索引着色器：Registry::objectIndex()->loadShaders( vp );// A uniform that will tell the shader which object to highlight:// 通过uniform变量，告诉着色器哪个对象要被高亮app.highlightUniform = new osg::Uniform("objectid_to_highlight", 0u);stateSet->addUniform(app.highlightUniform );
}//------------------------------------------------------------------------// Configures a window that lets you see what the RTT camera sees.
// 配置一个窗口，使您可以看到RTT相机所看到的内容。
void
setupRTTView(osgViewer::View* view, osg::Texture* rttTex)
{view->setCameraManipulator(0L);view->getCamera()->setName( "osgearth_pick RTT view" );view->getCamera()->setViewport(0,0,256,256);view->getCamera()->setClearColor(osg::Vec4(1,1,1,1));view->getCamera()->setProjectionMatrixAsOrtho2D(-.5,.5,-.5,.5);// 二维正投影view->getCamera()->setViewMatrixAsLookAt(osg::Vec3d(0,-1,0), osg::Vec3d(0,0,0), osg::Vec3d(0,0,1));view->getCamera()->setProjectionResizePolicy(osg::Camera::FIXED);// 固定// v 和 t，都是通过绘制2个三角形拼接为正方形osg::Vec3Array* v = new osg::Vec3Array(6);(*v)[0].set(-.5,0,-.5); (*v)[1].set(.5,0,-.5); (*v)[2].set(.5,0,.5); (*v)[3].set((*v)[2]); (*v)[4].set(-.5,0,.5);(*v)[5].set((*v)[0]);osg::Vec2Array* t = new osg::Vec2Array(6);(*t)[0].set(0,0); (*t)[1].set(1,0); (*t)[2].set(1,1); (*t)[3].set((*t)[2]); (*t)[4].set(0,1); (*t)[5].set((*t)[0]);osg::Geometry* g = new osg::Geometry();g->setUseVertexBufferObjects(true);g->setUseDisplayList(false);g->setVertexArray( v );        // 几何顶点坐标g->setTexCoordArray( 0, t );// 纹理坐标g->addPrimitiveSet( new osg::DrawArrays(GL_TRIANGLES, 0, 6) );// 通过绘制三角形方式绘制osg::Geode* geode = new osg::Geode();geode->addDrawable( g );osg::StateSet* stateSet = geode->getOrCreateStateSet();stateSet->setDataVariance(osg::Object::DYNAMIC);// 动态的stateSet->setTextureAttributeAndModes(0, rttTex, 1);rttTex->setUnRefImageDataAfterApply( false );rttTex->setResizeNonPowerOfTwoHint(false);GLUtils::setLighting(stateSet, 0);stateSet->setMode(GL_CULL_FACE, 0);stateSet->setAttributeAndModes(new osg::BlendFunc(GL_ONE, GL_ZERO), 1);const char* fs ="#version " GLSL_VERSION_STR "\n""void swap(inout vec4 c) { c.rgba = c==vec4(0)? vec4(1) : vec4(vec3((c.r+c.g+c.b+c.a)/4.0),1); }\n";osgEarth::Registry::shaderGenerator().run(geode);VirtualProgram::getOrCreate(geode->getOrCreateStateSet())->setFunction("swap", fs, ShaderComp::LOCATION_FRAGMENT_COLORING);view->setSceneData( geode );
}void startPicker(App& app)
{// Note! Must stop and restart threading when removing the picker// because it changes the OSG View/Slave configuration.// 当移动拾取器时，必须停止并重置线程。app.viewer.stopThreading();// 创建rtt拾取器app.picker = new RTTPicker();app.mainView->addEventHandler(app.picker);// add the graph that will be picked.// 添加将要被拾取的mapNodeapp.picker->addChild(app.mapNode);// install a callback that controls the picker and listens for hits.// 安装回调方法，它控制拾取器并侦听命中。app.picker->setDefaultCallback(new MyPickCallback(app));// Make a view that lets us see what the picker sees.// 创建视景器，让我们看到拾取器看到了什么。if (app.rttView == NULL){app.rttView = new osgViewer::View();app.rttView->getCamera()->setGraphicsContext(app.mainView->getCamera()->getGraphicsContext());app.rttView->getCamera()->setSmallFeatureCullingPixelSize(-1.0f);app.viewer.addView(app.rttView);  // 子视景器加入到主视景器中  }setupRTTView(app.rttView, app.picker->getOrCreateTexture(app.mainView));app.rttView->getCamera()->setNodeMask(~0);app.viewer.startThreading();// 开启主视景器线程
}// 停止拾取
void stopPicker(App& app)
{// Note! Must stop and restart threading when removing the picker// because it changes the OSG View/Slave configuration.app.viewer.stopThreading();//app.viewer.removeView(app.rttView);app.rttView->getCamera()->setNodeMask(0);app.mainView->removeEventHandler(app.picker);app.picker = 0L;// 停止拾取的状态app.viewer.startThreading();
}struct TogglePicker : public ui::ControlEventHandler
{App& _app;TogglePicker(App& app) : _app(app) { }// 点击拾取时，需要判断是否为拾取状态。处于停止状态，则开启；反之，则停止。void onClick(Control* button){if (_app.picker == 0L)// 当前处于停止拾取的状态startPicker(_app);elsestopPicker(_app);}
};//-----------------------------------------------------------------------int
usage(const char* name)
{OE_NOTICE << "\nUsage: " << name << " file.earth" << std::endl<< MapNodeHelper().usage() << std::endl;return 0;
}int
main(int argc, char** argv)
{osg::ArgumentParser arguments(&argc,argv);if ( arguments.read("--help") )return usage(argv[0]);App app(arguments);// 创建主视景器app.mainView = new osgViewer::View();app.mainView->setUpViewInWindow(30, 30, 1024, 1024, 0);app.mainView->getCamera()->setSmallFeatureCullingPixelSize(-1.0f);app.viewer.addView(app.mainView);app.mainView->getDatabasePager()->setUnrefImageDataAfterApplyPolicy( false, false );app.mainView->setCameraManipulator( new EarthManipulator() );    // Made some UI components: 制作一些ui控件ui::VBox* uiContainer = new ui::VBox();uiContainer->setAlign( ui::Control::ALIGN_LEFT, ui::Control::ALIGN_TOP );uiContainer->setAbsorbEvents( true );uiContainer->setBackColor(0,0,0,0.8);uiContainer->addControl( new ui::LabelControl("RTT Picker Test", osg::Vec4(1,1,0,1)) );uiContainer->addControl( new ui::ButtonControl("Toggle picker", new TogglePicker(app)) );// 控制是否允许拾取app.fidLabel = new ui::LabelControl("---");uiContainer->addControl( app.fidLabel );app.nameLabel = uiContainer->addControl( new ui::LabelControl( "---" ) );// Load up the earth file. 加载earth文件osg::Node* node = MapNodeHelper().load( arguments, &app.viewer, uiContainer );if ( node ){app.mainView->setSceneData( node );app.mapNode = MapNode::get(node);// start with a picker running 开始拾取startPicker(app);// Highlight features as we pick'em.installHighlighter(app); // 高亮app.mainView->getCamera()->setName( "Main view" );return app.viewer.run();}else{return usage(argv[0]);}
}

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osgEarth示例分析——osgearth_pick

前言

效果

代码分析

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