# Getting started with osgEarth

## Installation
The easiest way to install and use osgEarth is with the `vcpkg` package manager. There are two ways to go about it. But first...

### Update the OpenSceneGraph vcpkg build
OsgEarth depends on the OpenSceneGraph (OSG) SDK. OSG is available through vcpkg, but the confiruation is for OpenGL 2 and osgEarth needs to use OpenGL 3. So we need to make a simple change.

In the folder where you installed `vcpkg`, find the file `ports/osg/portfile.cmake`, and locate this block:
```
if(NOT DEFINED osg_OPENGL_PROFILE)
    set(osg_OPENGL_PROFILE "GL2")
endif()
```
Set the `osg_OPENGL_PROFILE` variable to `GL3`. You are now good to go.

### Method 1: Do it manually
You can install osgEarth manually using this command:
```
vcpkg install osgearth:x64-windows
```
Then you must set up your CMake configuration to point at the installed libraries.

### Method 2: Use the vcpkg toolchain
This approach sets up CMake to use the vcpkg toolchain, automating the installation of dependencies and making them local to your project. First you need a manifest file in your repository that looks like this:
#### vcpkg.json
```json
{
    "name": "myApp",
    "version-string": "0.1.0",
    "port-version": 1,
    "description": "Simple osgEarth demo application",
    "supports": "!(x86 | wasm32)",
    "dependencies": [ "osgearth" ]
}
```
You can add `vcpkg` dependencies as needed later on.

Next you need to bootstrap CMake to use the vcpkg toolchain, using a command like this. *Note, this is written as a Windows batch file.*
```bat
cmake ^
    -S %SOURCE_DIR% ^
    -B %BUILD_DIR% ^
    -G "Visual Studio 16 2019" ^
    -A x64 ^
    -DCMAKE_BUILD_TYPE=RelWithDebInfo ^
    -DCMAKE_INSTALL_PREFIX=%INSTALL_DIR% ^
    -DCMAKE_TOOLCHAIN_FILE=%VCPKG_TOOLCHAIN_FILE%
```
Customize this command and replace the variables above as needed:
* `SOURCE_DIR` - location of your root CMakeLists.txt file
* `BUILD_DIR` - out-of-source folder for build files
* `INSTALL_DIR` - location to install final executables and libraries
* `VCPKG_TOOLCHAIN_FILE` - The toolchain file found at `<vcpkg_install_dir>/scripts/buildsystems/vcpkg.cmake`.

Finally, run cmake to build your dependencies and generate your project files. This will take some time the first time you do it since it needs to download and compile osgEarth and all of its dependencies.
```
cmake <build_dir>
```

## Sample CMakeLists.txt
```cmake
cmake_minimum_required(VERSION 3.7)

project(
    myApp
    VERSION 0.1.0
    LANGUAGES CXX C
)

find_package(OpenSceneGraph REQUIRED COMPONENTS osg osgDB osgGA osgUtil osgViewer)

find_package(osgEarth CONFIG REQUIRED)

add_executable(myApp main.cpp)

target_link_libraries(myApp PRIVATE osgEarth)
target_link_libraries(myApp PRIVATE ${OPENSCENEGRAPH_LIBRARIES})

install(TARGETS myApp RUNTIME DESTINATION bin)
```

## Sample main.cpp
```c++
#include <osgEarth/MapNode>
#include <osgEarth/TMS>
#include <osgEarth/EarthManipulator>

#include <osg/ArgumentParser>
#include <osgViewer/Viewer>

int main(int argc, char** argv)
{
    osgEarth::initialize();
    
    osg::ArgumentParser args(&argc, argv);
    osgViewer::Viewer viewer(args);
    
    auto imagery = new osgEarth::TMSImageLayer();
    imagery->setURL("https://readymap.org/readymap/tiles/1.0.0/7/");
    
    auto mapNode = new osgEarth::MapNode();
    mapNode->getMap()->addLayer(imagery);
    
    viewer.setSceneData(mapNode);
    viewer.setCameraManipulator(new osgEarth::EarthManipulator(args));
    
    return viewer.run();
}
```