OSG交互：选中场景模型并高亮显示

1、目的

  可以在osg视图中选中指定模型实体，并高亮显示。共分为两种，一种鼠标点选，一种框选。

2、鼠标点选

2.1 功能说明

1. 生成两组对象，一组cow对象可以被选中，另一组robot不能被选中；
2. 点击cow对象被选中高亮，点击robot被选中不高亮；
3. 点击空白处，弹出“select nothing!”提示未选择任何实体；

备注：
  存在bug：当点击一个cow时，通过osg::PositionAttitudeTransform矩阵变换节点生成的另一个牛也被高亮，后续抽空来研究原因解决处理。

2.2 效果

效果如下：

2.3 源码

#include <osg/Geode>
#include <osg/Geometry>
#include <osg/LineWidth>
#include <osgViewer/Viewer>
#include <osgViewer/CompositeViewer>
#include <osgDB/ReadFile>
#include <osgDB/WriteFile>
#include <osgViewer/ViewerEventHandlers>  
#include <osg/Geode>
#include <osg/Geometry>
#include <osg/LineWidth>
#include <osgViewer/Viewer>
#include <osg/Node>
#include <osgDB/ReadFile>
#include <osgViewer/Viewer>
#include <osgDB/ReadFile>
#include <osgDB/WriteFile>
#include <osgViewer/ViewerEventHandlers> 
#include <osgViewer/CompositeViewer> 
#include <osg/PositionAttitudeTransform> 
#include <osg/MatrixTransform> 
#include <osgFX/Scribe> 
#include <osgParticle/PrecipitationEffect> 
#include <osg/NodeCallback> 
#include <osg/DrawPixels> 
#include <osg/ShapeDrawable>
#include <osg/ComputeBoundsVisitor>
#include <osgGA/TrackballManipulator>
#include <osgGA/StateSetManipulator>
#include <osg/GraphicsContext>
#include <osgViewer/GraphicsWindow>
#include <iostream>
#include <osgFX/Scribe>
#include <osgFX/Outline>
#include <osgViewer/ViewerEventHandlers>

#pragma comment(lib, "OpenThreadsd.lib")
#pragma comment(lib, "osgd.lib")
#pragma comment(lib, "osgDBd.lib")
#pragma comment(lib, "osgUtild.lib")
#pragma comment(lib, "osgGAd.lib")
#pragma comment(lib, "osgViewerd.lib")
#pragma comment(lib, "osgTextd.lib")
#pragma comment(lib, "osgSimd.lib")
#pragma comment(lib, "osgFXd.lib")

class nodePick :public osgGA::GUIEventHandler
{
	virtual bool handle(const osgGA::GUIEventAdapter& ea, osgGA::GUIActionAdapter& aa)
	{
		osgViewer::Viewer* viewer = dynamic_cast<osgViewer::Viewer*> (&aa);
		switch (ea.getEventType())
		{
		case osgGA::GUIEventAdapter::PUSH:
		{
			osgUtil::LineSegmentIntersector::Intersections intersections;
			osg::ref_ptr<osg::Node> node = new osg::Node();
			osg::ref_ptr<osg::Group> parent = new osg::Group();
			osg::ref_ptr<osg::Group> group0 = dynamic_cast<osg::Group*>(viewer->getSceneData()->asGroup()->getChild(0));
			if (viewer->computeIntersections(ea.getX(), ea.getY(), intersections))
			{
				//得到选择的节点
				osgUtil::LineSegmentIntersector::Intersection intersection = *intersections.begin();
				osg::NodePath& nodePath = intersection.nodePath;
				node = nodePath.back();

				// 判定所属的分组
				osg::ref_ptr<osg::Group> group = dynamic_cast<osg::Group*>(nodePath[2]);
				if (group->getName() == "groupCow")
				{
					//点击节点切换高亮
					parent = dynamic_cast<osg::Group*> (nodePath[nodePath.size() - 2]);//当前选择节点的父节点
					osgFX::Outline* ot = dynamic_cast<osgFX::Outline*>(parent.get());
					//若ot不存在（未高亮） (node->parent)=>(node->outline->parent)
					if (!ot) 
					{
						osg::ref_ptr<osgFX::Outline> outline = new osgFX::Outline();
						outline->setColor(osg::Vec4(1, 1, 0, 1));
						outline->setWidth(5);
						outline->addChild(node);
						parent->replaceChild(node, outline);
					}
					//若ot存在（高亮）找出当前outline的父节点（node->outline->*itr）=>(node->*itr)
					else
					{
						osg::Node::ParentList parentList = ot->getParents();
						osg::Node::ParentList::iterator itr = parentList.begin();
						(*itr)->replaceChild(ot, node);
					}
				}
			}
			else
			{
				std::cout << "select nothing!" << std::endl;
			}
		}
		default:
			return false;
		}
	}
};

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

	osg::ref_ptr<osg::Group> groupCow = new osg::Group;
	groupCow->setName("groupCow");

	osg::ref_ptr<osg::Group> groupRobot = new osg::Group;
	groupRobot->setName("groupRobot");

	osg::ref_ptr<osg::Node> cowNode = osgDB::readNodeFile("D:\\OpenSceneGraph_Data\\cow.osg");
	osg::ref_ptr<osg::Node> robotNode = osgDB::readNodeFile("D:\\OpenSceneGraph_Data\\robot.osg");

	osg::ref_ptr<osg::PositionAttitudeTransform> cowpatNode = new osg::PositionAttitudeTransform();
	cowpatNode->setPosition(osg::Vec3(0, 0, 0));
	cowpatNode->addChild(cowNode.get());
	cowpatNode->setName("cow1");

	osg::ref_ptr<osg::PositionAttitudeTransform> cowpatNode2 = new osg::PositionAttitudeTransform();
	cowpatNode2->setPosition(osg::Vec3(10, 0, 0));
	cowpatNode2->addChild(cowNode.get());
	cowpatNode2->setName("cow2");

	osg::ref_ptr<osg::PositionAttitudeTransform> robotpatNode = new osg::PositionAttitudeTransform();
	robotpatNode->setPosition(osg::Vec3(0, 10, 0));
	robotpatNode->addChild(robotNode.get());

	osg::ref_ptr<osg::PositionAttitudeTransform> robotpatNode2 = new osg::PositionAttitudeTransform();
	robotpatNode2->setPosition(osg::Vec3(10, 10, 0));
	robotpatNode2->addChild(robotNode.get());

	groupCow->addChild(cowpatNode);
	groupCow->addChild(cowpatNode2);

	groupRobot->addChild(robotpatNode);
	groupRobot->addChild(robotpatNode2);

	root->addChild(groupCow);
	root->addChild(groupRobot);

	viewer->setSceneData(root.get());
	viewer->addEventHandler(new nodePick);
	viewer->addEventHandler(new osgViewer::WindowSizeHandler());//F键控制全/半屏

	viewer->run();
}

3、鼠标框选

  参照osgChina站长杨石兴的博客代码。

3.1 功能说明

1. 生成20个圆球对象可被选中；
2. 点击鼠标+ctrl键可以绘制框选；
3. 框选实体变红；

备注：
  存在bug：卡顿、按F快捷键退出全屏，绘制出的框会偏离鼠标位置不随鼠标拖动、实用性不强需要改进。

3.2 效果

效果如下：
文章来源地址https://www.toymoban.com/news/detail-754615.html

3.3 源码

#include <osgViewer/Viewer>
#include <osgDB/ReadFile>
#include <osg/Camera>
#include <osgGA/GUIEventHandler>
#include <osg/Geode>
#include <osg/ShapeDrawable>
#include <osg/Geometry>
#include <algorithm>


//掩码为NODE_NPICK则不接受PICK，为NODE_PICK为接受PICK
#define NODE_NPICK ~0x0F
#define NODE_PICK 0x0F

//绘制一些球，用于被选择
class MySphere : public osg::Geode
{
public:
	MySphere(osg::Vec3 center, float radius)
	{
		_bSelect = false;
		_sd = new osg::ShapeDrawable(new osg::Sphere(center, radius));
		_sd->setColor(osg::Vec4(0.5, 0.5, 0.5, 1.0));
		addDrawable(_sd);
		setNodeMask(NODE_PICK);
	}

	//设置球是否被选择
	void setSelect(bool bSelect)
	{
		if (_bSelect == bSelect)
		{
			return;
		}

		_bSelect = bSelect;
		if (_bSelect)
		{
			_sd->setColor(osg::Vec4(1.0, 0.2, 0.2, 1.0));
			setNodeMask(NODE_NPICK);
		}
		else
		{
			_sd->setColor(osg::Vec4(0.5, 0.5, 0.5, 1.0));
			setNodeMask(NODE_PICK);
		}

		//重绘
		_sd->dirtyDisplayList();
	}

	osg::ShapeDrawable* _sd;
	bool _bSelect;
};

//用于选择的场景
osg::Node* g_selectNode = nullptr;

//绘制很多球
osg::Node* BuildScene()
{
	osg::Group* root = new osg::Group;

	//这些小球可以被选择
	g_selectNode = root;

	//绘制100个球
	for (int i = 0; i < 20; i++)
	{
		osg::Vec3 center(::rand() % 100, ::rand() % 100, ::rand() % 100);
		float r = ::rand() % 10 + 1.0;
		root->addChild(new MySphere(center, r));
	}

	return root;
}

//清空点选状态
void ClearSelect()
{
	for (int i = 0; i < 20; i++)
	{
		((MySphere*)g_selectNode->asGroup()->getChild(i))->setSelect(false);
	}
}

//结点的掩码，显示与隐藏
#define NODE_SHOW ~0x0
#define NODE_HIDE 0x0

//选择框做为一个全局变量，使用起来方便
osg::Geometry* g_geomSelectBox = new osg::Geometry;

//
osg::Camera* createHUD(osg::Viewport* vp)
{
	osg::Camera* camera = new osg::Camera;

	//设置投影矩阵为正交投影
	camera->setProjectionMatrix(osg::Matrix::ortho2D(0, vp->width(), 0, vp->height()));

	//设置其观察矩阵为单位矩阵，且不改变，该相机永远显示，也不用参与拣选
	camera->setReferenceFrame(osg::Transform::ABSOLUTE_RF);
	camera->setViewMatrix(osg::Matrix::identity());

	//只清空深度缓存，使得其显示内容可以以主相机为背景
	camera->setClearMask(GL_DEPTH_BUFFER_BIT);

	//最后渲染，因为需要以主相机显示的内容为背景
	camera->setRenderOrder(osg::Camera::POST_RENDER);

	//不需要响应事件
	camera->setAllowEventFocus(false);

	//绘制选择框
	osg::Geode* gnode = new osg::Geode;
	camera->addChild(gnode);

	gnode->addDrawable(g_geomSelectBox);
	//设置透明
	osg::StateSet* ss = gnode->getOrCreateStateSet();
	ss->setMode(GL_BLEND, osg::StateAttribute::ON | osg::StateAttribute::OVERRIDE);
	ss->setRenderingHint(osg::StateSet::TRANSPARENT_BIN);
	ss->setMode(GL_LIGHTING, osg::StateAttribute::OFF | osg::StateAttribute::OVERRIDE);

	//设置顶点
	osg::Vec3Array* vertices = new osg::Vec3Array;
	float depth = -0.1;
	vertices->push_back(osg::Vec3(0, 0, depth));
	vertices->push_back(osg::Vec3(100, 0, depth));
	vertices->push_back(osg::Vec3(100, 100, depth));
	vertices->push_back(osg::Vec3(0, 100, depth));
	g_geomSelectBox->setVertexArray(vertices);

	//设置颜色
	osg::Vec4Array* color = new osg::Vec4Array;
	color->push_back(osg::Vec4(0.8, 0.8, 0.8, 0.2));
	g_geomSelectBox->setColorArray(color, osg::Array::BIND_OVERALL);

	//绘制盒子
	g_geomSelectBox->addPrimitiveSet(new osg::DrawArrays(GL_QUADS, 0, 4));

	return camera;
}

class MyEvent : public osgGA::GUIEventHandler
{
public:
	MyEvent() :osgGA::GUIEventHandler(),
		_xStart(0),
		_yStart(0)
	{
	}

	virtual bool handle(const osgGA::GUIEventAdapter& ea, osgGA::GUIActionAdapter& aa)
	{
		//左ctrl按着，又鼠标点击，则进入绘制状态
		if (ea.getEventType() == ea.PUSH) //
		{
			//判断左CTRL键是否按下
			if (ea.getModKeyMask() == ea.MODKEY_LEFT_CTRL)
			{
				_xStart = ea.getX();
				_yStart = ea.getY();
				//清空之前绘制的结果，这里仅隐藏即可
				g_geomSelectBox->setNodeMask(NODE_HIDE);

				//清空点选内容，一切重新开始
				_pickArea.clear();
				ClearSelect();

				//返回真代表后续事件处理器包括操作器不再处理该事件，就实现了拖动时场景不动
				return true;
			}
		}

		//左ctrl点下时，进入到选择状态，开始绘制选择框，且操作器不再处理鼠标拖动事件
		if (ea.getEventType() == ea.DRAG) //鼠标拖动，拖动是鼠标按键按下的时候移动鼠标
		{
			//判断左CTRL键是否按下
			if (ea.getModKeyMask() == ea.MODKEY_LEFT_CTRL)
			{
				//开始绘制，调整顶点参数就可以
				g_geomSelectBox->setNodeMask(NODE_SHOW);

				//获取顶点、更新顶点
				osg::Vec3Array* vertices = (osg::Vec3Array*)g_geomSelectBox->getVertexArray();
				int xEnd = ea.getX();
				int yEnd = ea.getY();
				float depth = -0.1;
				vertices->at(0).set(_xStart, _yStart, depth);
				vertices->at(1).set(xEnd, _yStart, depth);
				vertices->at(2).set(xEnd, yEnd, depth);
				vertices->at(3).set(_xStart, yEnd, depth);

				//重绘
				g_geomSelectBox->dirtyDisplayList();

				int xMin = _xStart > ea.getX() ? ea.getX() : _xStart;
				int xMax = _xStart < ea.getX() ? ea.getX() : _xStart;
				int yMin = _yStart > ea.getY() ? ea.getY() : _yStart;
				int yMax = _yStart < ea.getY() ? ea.getY() : _yStart;

				//将框选的区域压入到_pickArea
				for (int i = xMin; i <= xMax; i += 5)
				{
					for (int j = yMin; j <= yMax; j += 5)
					{
						if (!isPick(i, j))
						{
							_pickArea.push_back(osg::Vec2i(i, j));
							//进行pick
							osgViewer::View* view = dynamic_cast<osgViewer::View*>(&aa);
							osgUtil::LineSegmentIntersector::Intersections intersections;
							//只pick和NODE_PICK相&得true的
							if (view->computeIntersections(i, j, intersections, NODE_PICK))
							{
								for (osgUtil::LineSegmentIntersector::Intersections::iterator iter = intersections.begin();
									iter != intersections.end(); iter++)
								{
									osg::NodePath np = iter->nodePath;

									MySphere* ms = dynamic_cast<MySphere*>(np.at(np.size() - 1));
									if (ms)
									{
										ms->setSelect(true);
									}
								}
							}
						}

					}
				}

				//返回真代表后续事件处理器包括操作器不再处理该事件，就实现了拖动时场景不动
				return true;
			}
		}

		return false;
	}

	//看一个点是不是pick过,返回true是已经pick过
	bool isPick(int x, int y)
	{
		for (int i = 0; i < _pickArea.size(); i++)
		{
			if ((_pickArea.at(i).x() == x) && (_pickArea.at(i).y() == y))
			{
				return true;
			}
		}

		return false;
	}

	int _xStart, _yStart;

	//鼠标按下去的时候，再拖动，就把框选的区域内的点都压进去，用于pick
	std::vector<osg::Vec2i> _pickArea;
};


int main()
{
	osgViewer::Viewer viewer;

	osg::Group* root = new osg::Group;

	root->addChild(BuildScene());

	viewer.setSceneData(root);
	viewer.realize();

	//realize之后，上下文已经被初始化，可以获得视口大小
	//在此处获得视口大小是为了创建HUD时使其视口大小与创建的一致
	osg::Viewport* vp = viewer.getCamera()->getViewport();
	root->addChild(createHUD(vp));

	viewer.addEventHandler(new MyEvent);
	viewer.addEventHandler(new osgViewer::WindowSizeHandler());//F键控制全/半屏

	return viewer.run();
}

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