Osgeearth uses note 1 -- show a digital earth

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1. Overview

Osgeearth supports. Earth files, which hold the configuration XML of digital earth related information. Just read this configuration file, you can get the corresponding digital earth related effect directly. But in actual use, I still feel some inconvenience, some effects can't be saved, so it's better to use code to realize many times. OSG earth is based on the display of a digital earth.

2. Implementation

2.1. 3D display

The specific implementation code is as follows:

#include <Windows.h>
#include <iostream>
#include <string>

#include <osgViewer/Viewer>
#include <osgDB/ReadFile>

#include <osgEarth/MapNode>

#include <osgEarthDrivers/gdal/GDALOptions>
#include <osgEarthDrivers/cache_filesystem/FileSystemCache>
#include <osgEarth/ImageLayer>

#include <osgEarthUtil/EarthManipulator>

using namespace std;

int main()
{	   
	osgEarth::ProfileOptions profileOpts;
	
	//Map configuration: setting cache directory
	osgEarth::Drivers::FileSystemCacheOptions cacheOpts;
	string cacheDir = "D:/Work/OSGNewBuild/tmp";
	cacheOpts.rootPath() = cacheDir;

	//
	osgEarth::MapOptions mapOpts;
	mapOpts.cache() = cacheOpts;
	mapOpts.profile() = profileOpts;

	//Create map node
	osg::ref_ptr<osgEarth::Map> map = new osgEarth::Map(mapOpts);
	osg::ref_ptr<osgEarth::MapNode> mapNode = new osgEarth::MapNode(map);

	osgEarth::Drivers::GDALOptions gdal;
	gdal.url() = "D:/Work/OSGNewBuild/osgearth-2.10.1/data/world.tif";
	osg::ref_ptr<osgEarth::ImageLayer> layer = new osgEarth::ImageLayer("BlueMarble", gdal);
	map->addLayer(layer);

	osgViewer::Viewer viewer;
	viewer.setSceneData(mapNode);

	osg::ref_ptr< osgEarth::Util::EarthManipulator> mainManipulator = new osgEarth::Util::EarthManipulator;
	viewer.setCameraManipulator(mainManipulator);

	viewer.setUpViewInWindow(100, 100, 800, 600);

	return viewer.run();
}

There are two points worth noting here. One is that the cache mechanism is used to generate cache while browsing, so a cache directory is set; the other is that a base map data is loaded, which is brought in osgeearth. The operation effect is as follows:

2.2. Two dimensional display

In addition to displaying the three-dimensional digital earth, osgeearth can also be displayed as a plane map, just setting specific parameters. For example, a two-dimensional planar map is shown here as a web Mercator projection:

#include <Windows.h>
#include <iostream>
#include <string>

#include <osgViewer/Viewer>
#include <osgDB/ReadFile>

#include <osgEarth/MapNode>

#include <osgEarthDrivers/gdal/GDALOptions>
#include <osgEarthDrivers/cache_filesystem/FileSystemCache>
#include <osgEarth/ImageLayer>

#include <osgEarthUtil/EarthManipulator>

#include <gdal_priv.h>

using namespace std;

int main()
{		
	CPLSetConfigOption("GDAL_DATA", "D:/Work/OSGNewBuild/OpenSceneGraph-3.6.4/3rdParty/x64/gdal-data");
	
	string wktString = "EPSG:3857";			//web Mercator projection
	//string wktString = "EPSG:4326";			//wgs84
	osgEarth::ProfileOptions profileOpts;
	profileOpts.srsString() = wktString;
		
	//osgEarth::Bounds bs(535139, 3365107, 545139, 3375107);
	//osgEarth::Bounds bs(73, 3, 135, 53);
	//profileOpts.bounds() = bs;
		
	//Map configuration: setting cache directory
	osgEarth::Drivers::FileSystemCacheOptions cacheOpts;
	string cacheDir =  "D:/Work/OSGNewBuild/tmp";
	cacheOpts.rootPath() = cacheDir;
	
	//
	osgEarth::MapOptions mapOpts;   
	mapOpts.cache() = cacheOpts;
	mapOpts.coordSysType() = osgEarth::MapOptions::CSTYPE_PROJECTED;

	mapOpts.profile() = profileOpts;

	//Create map node
	osg::ref_ptr<osgEarth::Map> map = new osgEarth::Map(mapOpts);
	osg::ref_ptr<osgEarth::MapNode> mapNode = new osgEarth::MapNode(map);

	osgEarth::Drivers::GDALOptions gdal;
	gdal.url() = "D:/Work/OSGNewBuild/osgearth-2.10.1/data/world.tif";
	osg::ref_ptr<osgEarth::ImageLayer> layer = new osgEarth::ImageLayer("BlueMarble", gdal);
	map->addLayer(layer);  

	osgViewer::Viewer viewer;
	viewer.setSceneData(mapNode);

	osg::ref_ptr< osgEarth::Util::EarthManipulator> mainManipulator = new osgEarth::Util::EarthManipulator;
	viewer.setCameraManipulator(mainManipulator);
	
	viewer.setUpViewInWindow(100, 100, 800, 600);

	return viewer.run();
}

EPSG code of Web Mercator projection plane coordinate system is 3857, so you only need to pass in the corresponding code directly. For more complex or customized coordinate systems, you can also directly pass in wkt strings, because osgeearth processes spatial coordinate reference through GDAL, and GDAL processes spatial coordinate reference through proj4, so you need to set the environment variable GDAL at this time_ Data (refer to GDAL coordinate conversion).

The effect is as follows:

Obviously, like the features of the Web Mercator projection, the ellipsoid is projected into a square plane map.

Tags: Windows xml

Posted on Sun, 24 May 2020 04:05:47 -0700 by Eclesiastes