osgEarth目标选择
osgEarth目标拾取
本文展示了一种目标选择的方法。通过将osg::Node注册到osgEarth的对象管理器中，利用osgEarth的RTTPicker类以及重写的RTTPicker::Callback类，实现目标的选中，最后利用osgEarth::VirtualProgram类，将拾取的对象高亮显示。
本文主要解决以下问题：
- osgEarth::RTTPicker实现目标拾取
- RTTPicker::Callback回调解析
- osgEarth::VirtualProgram目标高亮显示
目录
- 1 前言
- 2 osgEarth::RTTPicker与RTTPicker::Callback实现目标拾取
- 3 osgEarth::VirtualProgram目标高亮显示
内容
- 1 前言
osgEarth中标注之类的鼠标拾取操作和普通的碰撞检测拾取不太一样，PlaceNode和其它的标注类型不是在通常的场景空间中渲染的，而是作为屏幕空间的叠加层来渲染的，不能通过碰撞检测获取求交的对象。
osgEarth中有一个例子Sample osgearth_pick，演示了如何通过RTTPicker技术实现场景中对象的选取。加入到场景中的矢量和注记都能用鼠标拾取到，但对于普通的模型数据却获取不到。可以通过注册的方式，将加入到场景中的osg::Node进行注册，osgEarth中ObjectIndex类管理着对象的注册，其提供了接口用于加入到场景中的osg::Node进行注册。
- 2 osgEarth::RTTPicker与RTTPicker::Callback实现目标拾取
首先osgEarth解析.earth文件从而构建场景，场景中可以有地形、影像、矢量、模型等数据，而本篇文章主要实现对模型数据的拾取；接着将拾取的节点进行注册；然后由鼠标进行目标拾取。
从外部earth文件导入节点：
如上为.earth文件中的内容，包含两个部分：模型图层和视点图层。模型图层采用Model关键字，其中url字段表示模型的位置路径，location字段表示模型上球的位置和viewpoints图层；视点图层用viewpoints关键字来表示，其包含了 name、heading、lat、long、height、pitch和range七个参数，分别表示图层名称、方位角、位置纬度、经度、高度、俯仰角、范围。
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)) );
app.fidLabel = new ui::LabelControl("---");
uiContainer->addControl( app.fidLabel );
app.nameLabel = uiContainer->addControl( new ui::LabelControl( "---" ) );
// Load up the earth file.
osg::Node* node = MapNodeHelper().load( arguments, &app.viewer, uiContainer );代码段2为从外部earth文件导入得到osg::Node的代码，得到的osg::Node包含两个子节点，分别为MapNode和Controls::ControlCanvas, ControlCanvas包含四个LabelControl和一个ButtonControl，用来控制对象拾取的开启与关闭，以及对象信息的展示。
接下来是开启目标拾取功能，同时实现对象的注册：
struct App
{
App(osg::ArgumentParser& args) : viewer(args), mainView(NULL),
mapNode(NULL), picker(NULL), fidLabel(NULL),
nameLabel(NULL), highlightUniform(NULL)
{ }
osgViewer::CompositeViewer viewer;
osgViewer::View* mainView;
osgEarth::MapNode* mapNode;
osgEarth::Util::RTTPicker* picker;
ui::LabelControl* fidLabel;
ui::LabelControl* nameLabel;
osg::Uniform* highlightUniform;
};void startPicker(App& app)
{
// Note! Must stop and restart threading when removing the picker
// because it changes the OSG View/Slave configuration.
app.viewer.stopThreading();
app.picker = new RTTPicker();
app.mainView->addEventHandler(app.picker);
ResistryNodeVisitor rn;
app.mapNode->accept(rn);
// add the graph that will be picked.
app.picker->addChild(app.mapNode);
// install a callback that controls the picker and listens for hits.
app.picker->setDefaultCallback(new MyPickCallback(app));
app.viewer.startThreading();
}代码段1为一结构体，主要包含一视图、主视图、MapNode以及Util::RTTPicker；代码段2为开启节点拾取功能，RTTPicker继承自osgGA::GUIEventHandler，可将其作为事件直接加入到视图中；ResistryNodeVisitor为一访问器，实现节点的注册，其核心代码为：osgEarth::Registry::objectIndex()->tagNode(&node, &node); tageNode的英文解释为：
/**
* Inserts the object into the index, and tags the Node with a uniform containing
* the object id. Returns the Object ID.
*/
即将一对象（第二个参数）插入到index表中，同时将 一osg::Uniform对象写入到节点中（第一个参数）。
最后设置RTTPicker的CallBack。RTTPicker类继承自osgGA::GUIEventHandler，其重写了handle函数，handle函数中调用了runPicks函数，runPicks调用了checkForPickResult函数，checkForPickResult函数调用了RTTPlicker::CallBack中的onHit函数，本文通过重写RTTPicker::CallBack中的onHit()函数实现拾取对象的获取：
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(id).get();
Feature* feature = index ? index->getFeature( id ) : 0L;
if ( feature )
{
_app.fidLabel->setText( Stringify() << "Feature ID = " << feature->getFID() << " (oid = " << id << ")" );
_app.nameLabel->setText( Stringify() << "Name = " << feature->getString("name") );
}
else
{
// Check whether it's an annotation:
AnnotationNode* anno = Registry::objectIndex()->get(id).get();
if ( anno )
{
_app.fidLabel->setText( Stringify() << "ObjectID = " << id );
_app.nameLabel->setName( Stringify() << "Name = " << anno->getName() );
}
// None of the above.. clear.
else
{
_app.fidLabel->setText( Stringify() << "unknown oid = " << id );
_app.nameLabel->setText( " " );
}
}
_app.highlightUniform->set( id );
}
void onMiss()
{
_app.fidLabel->setText( "No pick." );
_app.nameLabel->setText( " " );
_app.highlightUniform->set( 0u );
}
// pick whenever the mouse moves.
bool accept(const osgGA::GUIEventAdapter& ea, const osgGA::GUIActionAdapter& aa)
{
return ea.getEventType() == ea.PUSH;
}
}; 其中onHit函数通过objectId获取对应的节点，最后将高亮显示的节点设置为对应的id（_app.highlightUniform->set( id )）。
-
3 osgEarth::VirtualProgram目标高亮显示
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";
void installHighlighter(App& app)
{
osg::StateSet* stateSet = app.mapNode->getOrCreateStateSet();
int attrLocation = Registry::objectIndex()->getObjectIDAttribLocation();
// This shader program will highlight the selected object.
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:
Registry::objectIndex()->loadShaders( vp );
// A uniform that will tell the shader which object to highlight:
app.highlightUniform = new osg::Uniform("objectid_to_highlight", 0u);
stateSet->addUniform(app.highlightUniform );
}
通过VirtualProgram设置节点着色器和片元着色器，实现对特定ID的节点，高亮显示。
最后完整代码如下：
/* -*-c++-*- */
/* osgEarth - Geospatial SDK for OpenSceneGraph
* Copyright 2020 Pelican Mapping
* http://osgearth.org
*
* osgEarth is free software; you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
* IN THE SOFTWARE.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this program. If not, see
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#define LC "[rttpicker] "
using namespace osgEarth;
using namespace osgEarth::Util;
namespace ui = osgEarth::Util::Controls;
//-----------------------------------------------------------------------
//! Application-wide data.
struct App
{
App(osg::ArgumentParser& args) : viewer(args), mainView(NULL),
mapNode(NULL), picker(NULL), fidLabel(NULL),
nameLabel(NULL), highlightUniform(NULL)
{ }
osgViewer::CompositeViewer viewer;
osgViewer::View* mainView;
osgEarth::MapNode* mapNode;
osgEarth::Util::RTTPicker* picker;
ui::LabelControl* fidLabel;
ui::LabelControl* nameLabel;
osg::Uniform* highlightUniform;
};
//! Callback that you install on the RTTPicker.
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(id).get();
Feature* feature = index ? index->getFeature( id ) : 0L;
if ( feature )
{
_app.fidLabel->setText( Stringify() << "Feature ID = " << feature->getFID() << " (oid = " << id << ")" );
_app.nameLabel->setText( Stringify() << "Name = " << feature->getString("name") );
}
else
{
// Check whether it's an annotation:
AnnotationNode* anno = Registry::objectIndex()->get(id).get();
if ( anno )
{
_app.fidLabel->setText( Stringify() << "ObjectID = " << id );
_app.nameLabel->setName( Stringify() << "Name = " << anno->getName() );
}
// None of the above.. clear.
else
{
_app.fidLabel->setText( Stringify() << "unknown oid = " << id );
_app.nameLabel->setText( " " );
}
}
_app.highlightUniform->set( id );
}
void onMiss()
{
_app.fidLabel->setText( "No pick." );
_app.nameLabel->setText( " " );
_app.highlightUniform->set( 0u );
}
// pick whenever the mouse moves.
bool accept(const osgGA::GUIEventAdapter& ea, const osgGA::GUIActionAdapter& aa)
{
return ea.getEventType() == ea.PUSH;
}
};
//-----------------------------------------------------------------------
// Shaders that will highlight the currently "picked" feature.
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";
void installHighlighter(App& app)
{
osg::StateSet* stateSet = app.mapNode->getOrCreateStateSet();
int attrLocation = Registry::objectIndex()->getObjectIDAttribLocation();
// This shader program will highlight the selected object.
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:
Registry::objectIndex()->loadShaders( vp );
// A uniform that will tell the shader which object to highlight:
app.highlightUniform = new osg::Uniform("objectid_to_highlight", 0u);
stateSet->addUniform(app.highlightUniform );
}
class ResistryNodeVisitor : public osg::NodeVisitor
{
public:
ResistryNodeVisitor()
: osg::NodeVisitor(TRAVERSE_ALL_CHILDREN)
{
}
~ResistryNodeVisitor()
{
}
void apply(osg::Geometry& node)
{
osgEarth::Registry::objectIndex()->tagNode(&node, &node);
//_geometries.push_back(&node);
traverse(node);
}
public:
/*const std::vector >& pagedlods()
{
return _pagedlods;
}
const std::vector >& geometries()
{
return _geometries;
}
void clear()
{
_geometries.clear();
_pagedlods.clear();
}*/
private:
/*std::vector > _geometries;
std::vector > _pagedlods;*/
};
//------------------------------------------------------------------------
// Configures a window that lets you see what the RTT camera sees.
//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);
// view->getCamera()->setViewMatrixAsLookAt(osg::Vec3d(0,-1,0), osg::Vec3d(0,0,0), osg::Vec3d(0,0,1));
// view->getCamera()->setProjectionResizePolicy(osg::Camera::FIXED);
//
// 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 );
// g->setTexCoordArray( 0, t );
// g->addPrimitiveSet( new osg::DrawArrays(GL_TRIANGLES, 0, 6) );
//
// osg::Geode* geode = new osg::Geode();
// geode->addDrawable( g );
//
// osg::StateSet* stateSet = geode->getOrCreateStateSet();
// stateSet->setDataVariance(osg::Object::DYNAMIC);
//
// 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.
app.viewer.stopThreading();
app.picker = new RTTPicker();
app.mainView->addEventHandler(app.picker);
ResistryNodeVisitor rn;
app.mapNode->accept(rn);
// add the graph that will be picked.
app.picker->addChild(app.mapNode);
// install a callback that controls the picker and listens for hits.
app.picker->setDefaultCallback(new MyPickCallback(app));
// Make a view that lets us see what the picker sees.
/* 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);
}
setupRTTView(app.rttView, app.picker->getOrCreateTexture(app.mainView));
app.rttView->getCamera()->setNodeMask(~0);*/
app.viewer.startThreading();
}
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;
app.viewer.startThreading();
}
struct TogglePicker : public ui::ControlEventHandler
{
App& _app;
TogglePicker(App& app) : _app(app) { }
void onClick(Control* button)
{
if (_app.picker == 0L)
startPicker(_app);
else
stopPicker(_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);
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:
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)) );
app.fidLabel = new ui::LabelControl("---");
uiContainer->addControl( app.fidLabel );
app.nameLabel = uiContainer->addControl( new ui::LabelControl( "---" ) );
// Load up the earth file.
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
startPicker(app);
// Highlight features as we pick'em.
installHighlighter(app);
app.mainView->getCamera()->setName( "Main view" );
return app.viewer.run();
}
else
{
return usage(argv[0]);
}
}
运行的结果如下：
总结：
本文介绍了osgEarth中目标拾取的用法，通过重写RTTPicker::CallBack，获取拾取的对象，然后借用shader将拾取的对象高亮。本文只介绍了osgEarth目标拾取的用法，接下来会进一步分析其原理，研究RTTPicker类及osgEarth的注册系统。