urho3d/Docs/GettingStarted.dox

/**

\page Building Building Urho3D

\section Building_Prerequisites Building prerequisites

Although all required third-party libraries are included as source code, there are system-level dependencies that must be satisfied before Urho3D can be built successfully:

- For Windows, the DirectX SDK needs to be installed and its include and library directories set as Visual Studio global directories (Tools -> Options -> Projects and Solutions -> VC++ Directories in VS2008.)

- For Linux, the following development packages need to be installed: libx11-dev, libxrandr-dev, libasound2-dev. Also install the package libgl1-mesa-dev if your GPU driver does not include OpenGL headers & libs.

- For Mac OS X, the Xcode developer tools package should include everything necessary.

- For Android, the Android SDK and Android NDK need to be installed.

To run Urho3D, the minimum system requirements are:

- Windows: CPU with SSE instructions support, Windows XP or newer, DirectX 9.0c, GPU with %Shader %Model 2 support (%Shader %Model 3 recommended.)

- Linux & Mac OS X: GPU with OpenGL 2.0 support, EXT_framebuffer_object and EXT_packed_depth_stencil extensions.

- Android: OS version 2.2 or newer, OpenGL ES 2.0 capable GPU.

- iOS: OpenGL ES 2.0 capable GPU.

For Windows, SSE and Windows XP requirements can be eliminated by disabling SSE, crash dump support and file watcher from the root CMakeLists.txt. Windows 2000 will then be the absolute minimum.

\section Building_Desktop Desktop build process

Urho3D uses CMake (http://www.cmake.org) to build. The process has two steps:

1) Run CMake in the root directory with your preferred toolchain specified to generate the build files. You can use the batch files or shell scripts provided: cmake_vs2008.bat or cmake_vs2010.bat on Windows, and cmake_gcc.sh on Linux and Mac OS X.

2) For Visual Studio, open Urho3D.sln and build the configuration(s) you like. For gcc, execute make (by default, cmake_gcc.sh specifies to make a RelWithDebInfo build.)

When using Xcode on Mac OS X, select the i386 architecture before building. Compiling Urho3D as 64-bit is not supported.

After the build is complete, the programs can be run from the Bin directory.

To run from the Visual Studio debugger, set the Urho3D project as the startup project and enter its relative path and filename into Properties -> Debugging -> Command: ..\\Bin\\Urho3D.exe. Additionally, entering -w into Debugging -> Command Arguments is highly recommended. This enables startup in windowed mode: without it running into an exception or breakpoint will be obnoxious as the mouse cursor will likely be hidden.

To actually make Urho3D.exe do something useful, it must be supplied with the name of the script file it should load and run. You can try for example the following arguments: Scripts/TestScene.as -w

To make the Urho3D examples start faster on Windows & Direct3D9 mode, run CompileAllShaders.bat from the Bin directory first.

\section Building_Android Android build process

First copy Bin/Data and Bin/CoreData directories to the Android/assets directory (you can use the provided batch file CopyData.bat.) Next, execute the following commands in the Android directory:

- android update project -p . (only needed on the first time)
- ndk-build
- ant debug

Note that ndk-build builds Urho3D twice, once without hardware floating point instructions, and once with them. After the commands finish successfully, the APK should have been generated to the Android/bin directory, from where it can be installed on a device or an emulator.

For a release build, use the "ant release" command instead of "ant debug" and follow the Android SDK instructions on how to sign your APK properly.

By default the Android package for Urho3D is com.googlecode.urho3d. For a real application you must replace this with your own package name. Unfortunately the name has to be replaced in several files:

- Android/AndroidManifest.xml
- Android/src/com/googlecode/urho3d/SDLActivity.java (rename directories also)
- ThirdParty/SDL/include/SDL_config_android.h, look for the NATIVE_FUNCTION macro

\section Building_Ios iOS build process

Run cmake_ios.sh. This generates an Xcode project named Urho3D.xcodeproj.

Open the Xcode project and check the properties for the Urho3D project (topmost in the Project Navigator.) In Architectures -> Base SDK, choose your iOS SDK. In Code Signing, enter your developer identity as necessary.

The Urho3D target will actually build the application bundle and copy resources from Bin/Data and Bin/CoreData directories. Edit its build scheme to choose debug or release mode.

Note that due to a CMake / Xcode bug, you may need to modify and save Urho3D.cpp after modifying any of the libraries to get Xcode to re-link the executable. Do this also if you modify the data files and get an error about resources having been added or modified after signing.


\page Running Running Urho3D

The main executable Urho3D.exe in the Bin directory contains all the engine runtime functionality. However, it does not contain any inbuilt logic or application, and therefore must be supplied with the name of the application script file it should run:

Urho3D.exe <scriptfilename> [options]

The scripting language used is AngelScript (http://www.angelcode.com/angelscript); the script files have .as extension and need to be placed under either the Bin/Data or Bin/CoreData subdirectories so that Urho3D.exe can find them. An application script is required to have the function void Start(), which will be executed before starting the engine main loop. It is this function's responsibility to initialize the application and to hook up to any necessary \ref Events "events", such as the update that happens every frame.

On Android and iOS there are no command line options, so running the NinjaSnowWar example is hardcoded. This can be changed from the file Urho3D/Urho3D.cpp.

Currently, five example application scripts exist:

\section Running_TestScene TestScene

Rendering, physics and serialization test. To start, run TestScene.bat in the Bin directory, or use the command Urho3D.exe Scripts/TestScene.as

Key and mouse controls:

\verbatim
WSAD        Move
Left mouse  Create a new physics object; characters will ragdoll when hit
Right mouse Hold and move mouse to rotate view
Shift+LMB   Paint a decal into the mouse cursor hit location
Space       Toggle debug geometry
F1          Toggle AngelScript console
F5          Save scene
F7          Load scene
1 to 9      Toggle rendering options
T           Toggle profiling display
O           Toggle orthographic camera
F           Toggle FXAA edge filter
B           Toggle bloom post-process
P           Toggle scene animation (TestSceneOld only)
L           Toggle camera light detached/attached (TestSceneOld only)
\endverbatim

TestScene also includes a network replication test, where clients can connect, move around as invisible cameras, and create new physics objects. For this, a server needs to be started with the command TestScene.bat server (-headless switch can optionally given so that the server will not open a graphics window) and clients can connect by specifying the server address on the command line, for example TestScene.bat 127.0.0.1

There is also a variation of TestScene ported from Urho3D 1.0, TestSceneOld. It lacks networking features, but is provided for examining backward compatibility and performance. It can be run with TestSceneOld.bat or by using the command Urho3D.exe Scripts/TestSceneOld.as

\section Running_NinjaSnowWar NinjaSnowWar

A third-person action game. To start, run NinjaSnowWar.bat in the Bin directory, or use the command Urho3D.exe Scripts/NinjaSnowWar.as

Key and mouse controls:

\verbatim
WSAD        Move
Left mouse  Attack
Space       Jump
F1          Toggle AngelScript console
F2          Toggle physics debug geometry
F3          Toggle profiling display
F4          Toggle octree debug geometry
\endverbatim

If a joystick is connected, it can also be used for controlling the player character.

NinjaSnowWar also supports client/server multiplayer. To start the server, run the command NinjaSnowWar.bat server (-headless switch can optionally given so that the server will not open a graphics window.) To connect to a server, specify the server address on the command line, for example NinjaSnowWar.bat 127.0.0.1

\section Running_Editor Editor

%Scene editor application written in script. To start, run Editor.bat, or use the command Urho3D.exe Scripts/Editor.as

\section Running_Chat Chat

Simple client-server chat test application. To start, run Chat.bat or ChatServer.bat in the Bin directory, or use the command Urho3D.exe Scripts/Chat.as

On the client, first type the server address to the text edit box and click "Connect." After connecting successfully you can start typing messages;
either press return or click "Send" to send them. Press ESC to exit.

To connect automatically, the server address can also be given on the command line, for example Chat.bat 127.0.0.1

For details on how to use the editor, see \ref EditorInstructions "Editor instructions."

\section Running_LightTest LightTest

%Light rendering performance test. To start, run LightTest.bat in the Bin directory, or use the command Urho3D.exe Scripts\LightTest.as

Key and mouse controls:

\verbatim
WSAD        Move
ZX          Select model to use
Arrows      Add or remove lights and objects
Pageup/down Add or remove 10 lights
Right mouse Hold and move mouse to rotate view
F1          Toggle AngelScript console
1 to 9      Toggle rendering options
T           Toggle profiling display
V           Toggle vertex lighting
C           Toggle orthographic camera
F           Toggle FXAA edge filter
R           Re-randomize light and object positions
\endverbatim

\section Running_Commandline Command line options

Urho3D.exe understands the following command line options:

\verbatim
-x<res>     Horizontal resolution
-y<res>     Vertical resolution
-m<level>   Enable hardware multisampling
-v          Enable vertical sync
-t          Enable triple buffering
-w          Start in windowed mode
-b<length>  Sound buffer length in milliseconds
-r<freq>    Sound mixing frequency in Hz
-headless   Headless mode. No application window will be created
-logdebug   Display debug level log messages also in release mode
-prepass    Use light pre-pass rendering
-deferred   Use deferred rendering
-lqshadows  Use low-quality (1-sample) shadow filtering
-noshadows  Disable shadow rendering
-nolimit    Disable frame limiter
-nothreads  Disable worker threads
-nosound    Disable sound output
-noip       Disable sound mixing interpolation
-sm2        Force SM2.0 rendering
\endverbatim


\page Structure Overall structure

Urho3D consists of several static libraries that are independent where possible: for example the Graphics library could be used without the Engine library, if only rendering capabilities were desired.

The libraries are the following:

- Container. Provides STL replacement classes and shared pointers.
- Math. Provides vector & quaternion types and geometric shapes used in intersection tests.
- Core. Provides the execution Context, the base class Object for typed objects, object factories, \ref Event "event handling", threading and profiling.
- IO. Provides file system access, stream input/output and logging.
- %Resource. Provides the ResourceCache and the base resource types, including XML documents.
- %Scene. Provides Node and Component classes, from which Urho3D scenes are built.
- %Graphics. Provides application window handling and 3D rendering capabilities.
- %Input. Provides mouse & keyboard input in both polled and event-based mode.
- %Network. Provides client-server networking functionality.
- %Audio. Provides the audio subsystem and playback of .wav & .ogg sounds in either 2D or 3D.
- Physics. Provides physics simulation.
- %Script. Provides scripting support using the AngelScript language.
- %Engine. Instantiates the subsystems from the libraries above, and manages the main loop iteration.

Urho3D.exe uses the Engine & Script libraries to start up the subsystems and to load the script file specified on the command line; however all of the libraries above get automatically linked as Engine library depends on all of them.

Although Urho3D.exe itself is geared towards running a scripted application, it is also possible to use the engine through C++ only. When the scripting subsystem initialization is completely skipped, the resulting executable will also be significantly smaller.

The third-party libraries are used for the following functionality:

- AngelScript: scripting language implementation
- Bullet: physics simulation implementation
- FreeType: font rendering
- GLee: OpenGL extensions handling
- kNet: UDP networking
- libcpuid: CPU properties detection
- Open Asset Import Library: reading various 3D file formats
- pugixml: parsing XML files
- SDL: window and OpenGL context creation, input and sound output
- StanHull: convex hull generation from triangle meshes, used for physics collision shapes
- stb_image: image loading
- stb_vorbis: Ogg Vorbis decoding


\page Conventions Conventions

Urho3D uses the following conventions and principles:

- Left-handed coordinates. Positive X, Y & Z axes point to the right, up, and forward, and positive rotation is clockwise.

- Degrees are used for angles.

- Clockwise vertices define a front face.

- %Audio volume is specified from 0.0 (silence) to 1.0 (full volume)

- Path names use slash instead of backslash. Paths will be converted internally into the necessary format when calling into the operating system.

- In the script API, properties are used whenever appropriate instead of %Set... and Get... functions. If the setter and getter require index parameters, the property will use array-style indexing, and its name will be in plural. For example model->SetMaterial(0, myMaterial) in C++ would become model.materials[0] = myMaterial in script.

- Raw pointers are used whenever possible in the classes' public API. This simplifies exposing functions & classes to script, and is relatively safe, because SharedPtr & WeakPtr use intrusive reference counting.

- No C++ exceptions. Error return values (false / null pointer / dummy reference) are used instead. %Script exceptions are used when there is no other sensible way, such as with out of bounds array access.

- Feeding illegal data to public API functions, such as out of bounds indices or null pointers, should not cause crashes or corruption. Instead errors are logged as appropriate.

- For threading and multi-instance safety, no mutable static data (including singletons) or function-static data is allowed.

- Third party libraries are included as source code for the build process. They are however hidden from the public API as completely as possible.

For more details related to the C++ coding style, see also \ref CodingConventions "Coding conventions".


\page ScriptQuickstart Quickstart in script

In the following example, a minimal "Hello World" application with both 3D and user interface content will be built.

We start by defining the Start() function required in all Urho3D script applications. When Urho3D.exe executes it, all the engine subsystems are already in place, so any initialization that needs to be done is specific to the application itself.

\code
Scene@ helloScene;

void Start()
{
    helloScene = Scene();

    CreateObjects();
    CreateText();
    SubscribeToEvents();
}
\endcode

Even before Start(), we define the object handle for the 3D scene we are going to create. This must be outside the function so that the Scene will remain after the function execution ends. Angelscript uses the @ symbol for object handles, which correspond to SharedPtr's on C++ side (ie. they keep alive the object pointed to.)

In the Start() function itself, first of all we create the 3D scene. Note the lack of "new" keyword. Then we branch off to further initialization functions that will be defined below.

Note that Urho3D has modified AngelScript to allow object handle assignment without the @ symbol, if the object in question does not support value assignment. None of the Urho3D reference-counted objects, such as Scene, support value assignment. In unmodified AngelScript the first line of Start() would have to read "@helloScene = Scene()".

In CreateObjects(), which we define next, the scene will be filled with some content. The Urho3D scene model is basically a scene graph; the Scene object serves also as the root node.

\code
void CreateObjects()
{
    helloScene.CreateComponent("Octree");

    Node@ objectNode = helloScene.CreateChild();
    Node@ lightNode = helloScene.CreateChild();
    Node@ cameraNode = helloScene.CreateChild();

    StaticModel@ object = objectNode.CreateComponent("StaticModel");
    object.model = cache.GetResource("Model", "Models/Mushroom.mdl");
    object.material = cache.GetResource("Material", "Materials/Mushroom.xml");

    Light@ light = lightNode.CreateComponent("Light");
    light.lightType = LIGHT_DIRECTIONAL;
    lightNode.direction = Vector3(-1, -1, -1);

    Camera@ camera = cameraNode.CreateComponent("Camera");
    cameraNode.position = Vector3(0, 0.3, -3);

    renderer.viewports[0] = Viewport(helloScene, camera);
}
\endcode

First of all we need to create an Octree component into the root node. This is used for accelerated visibility queries to check what the camera "sees", and without it nothing would be visible.

Three child nodes are then created: one for a 3D model object, one for a directional light, and one for the camera. The scene nodes themselves display nothing in the 3D world; components need to be created into them for the actual visible content.

Child nodes can be created with or without names; uniqueness of names is not enforced. In this case we opt to not use names, as we do not need to find the nodes later after creation.

As animation is not needed, we use a StaticModel component for the 3D model. Its scene node remains at the origin (default position of each scene node.) The ResourceCache subsystem is used to load the needed Model & Material resources.

The light scene node also remains at the origin. Position does not matter for directional lights, but the node's forward direction is adjusted so that the light will shine down diagonally.

The camera's scene node is pulled back along the Z-axis to be able to see the object.

Finally we define a fullscreen Viewport into the Renderer subsystem so that the scene can be shown. The viewport needs Scene and Camera object handles. Note the indexing; multiple viewports could be defined (for example to use split screen rendering) if necessary.

The 3D content is now finished. Next, we create the user interface content in CreateText().

\code
void CreateText()
{
    Text@ helloText = Text();
    helloText.SetFont(cache.GetResource("Font", "Fonts/Anonymous Pro.ttf"), 30);
    helloText.text = "Hello World from Urho3D";
    helloText.color = Color(0, 1, 0);
    helloText.horizontalAlignment = HA_CENTER;
    helloText.verticalAlignment = VA_CENTER;

    ui.root.AddChild(helloText);
}
\endcode

We display a "Hello World" message on the screen with the help of a Text user interface element. We use the included Anonymous Pro font with point size 30.  For the text to actually become visible, it needs to be added as a child of the user interface root element (the UI can be thought of as a 2D scene graph.) It is also centered both horizontally and vertically in relation to the parent element.

Finally we subscribe to necessary Urho3D events in the SubscribeToEvents() function.

\code
void SubscribeToEvents()
{
    SubscribeToEvent("Update", "HandleUpdate");
}
\endcode

If no events would be responded to, the application would just be left running with no possibility to interact with it, until it was forcibly exited with Alt-F4. In this case, we are interested of the frame update event, which will be sent on each iteration of the main loop. When subscribing, we need to give the name of the event, and the name of the event handler function. We could also require the event to be sent by a specific sender, but in this case that is unnecessary.

The event handler function needs to have a specific signature. If event type and parameters are not needed, "void HandleEvent()", or if they are, "void HandleEvent(StringHash eventType, VariantMap& eventData)". We might want to expand the application later, so we use the latter form.

\code
void HandleUpdate(StringHash eventType, VariantMap& eventData)
{
    float timeStep = eventData["TimeStep"].GetFloat();

    if (input.keyPress[KEY_ESC])
        engine.Exit();
}
\endcode

The current frame's delta time is sent in the update event's parameters, and that will be useful when animating the scene. For now the event handler simply checks from the Input subsystem if the ESC key has been pressed; if it is, it calls the Engine subsystem's \ref Engine::Exit "Exit()" function. This closes the application window and causes Urho3D.exe to exit after the current main loop iteration finishes.

Note that to get the ESC keypress without having to poll it for each frame, we could also subscribe to the "KeyDown" event sent by the Input subsystem.

The example application is now complete. To try it out, save it as HelloWorld.as in the Bin/Data/Scripts directory, then run Urho3D.exe Scripts/HelloWorld.as


\page CppQuickstart Quickstart in C++

This example shows how to create an Urho3D C++ application from the ground up. The actual functionality will be the same as in \ref ScriptQuickstart "Quickstart in script"; it is strongly recommended that you familiarize yourself with it first.

For simplicity, the application is assumed to be compiled on Windows and therefore defines the WinMain() function; look at the file Urho3D.cpp in the Urho3D subdirectory on how to handle cross-platform startup using a macro defined in Main.h in the Core library.

To start with, create a subdirectory "HelloWorld" into the Urho3D root directory, and add the following line to the root directory's CMakeLists.txt %file:

\code
add_subdirectory (HelloWorld)
\endcode

Then, create the following CMakeLists.txt file into the HelloWorld directory (mostly copied from CMakeLists.txt of Urho3D.exe):

\code
# Define target name
set (TARGET_NAME HelloWorld)

# Define source files
file (GLOB CPP_FILES *.cpp)
file (GLOB H_FILES *.h)
set (SOURCE_FILES ${CPP_FILES} ${H_FILES})

# Include directories
include_directories (
    ../Engine/Container ../Engine/Core ../Engine/Engine ../Engine/Graphics ../Engine/Input ../Engine/IO
    ../Engine/Math ../Engine/Resource ../Engine/Scene ../Engine/UI
)

# Define target & libraries to link
add_executable (${TARGET_NAME} WIN32 ${SOURCE_FILES})
target_link_libraries (${TARGET_NAME} Container Core Engine Graphics Input IO Math Resource Scene UI)
finalize_exe ()
\endcode

Before recreating the build files with CMake, create an empty HelloWorld.cpp into the HelloWorld directory. Now you can re-run CMake. If using Visual Studio, the HelloWorld project should now appear in the Urho3D solution, and you can start writing the actual application into HelloWorld.cpp.

To start with, we need the include files for all the engine classes we are going to use, plus Windows.h for the WinMain function:

\code
#include "Camera.h"
#include "Context.h"
#include "CoreEvents.h"
#include "Engine.h"
#include "Font.h"
#include "Input.h"
#include "Light.h"
#include "Material.h"
#include "Model.h"
#include "Octree.h"
#include "ProcessUtils.h"
#include "Renderer.h"
#include "ResourceCache.h"
#include "Scene.h"
#include "StaticModel.h"
#include "Text.h"
#include "UI.h"

#include <Windows.h>
\endcode

To be able to subscribe to events, we need to subclass Object (if we did not use events, we could do everything procedurally, for example directly in WinMain, but that would be somewhat ugly.) We name the class HelloWorld, with functions that match the script version, plus a constructor. Note the shared pointers to the scene that we will create, and to the ResourceCache, which is perhaps the most often used subsystem, and therefore convenient to store here. Also note the OBJECT(className) macro, which inserts code for object type identification:

\code
class HelloWorld : public Object
{
    OBJECT(HelloWorld);

public:
    HelloWorld(Context* context);
    void Start();
    void CreateObjects();
    void CreateText();
    void SubscribeToEvents();
    void HandleUpdate(StringHash eventType, VariantMap& eventData);

    SharedPtr<Scene> helloScene_;
    SharedPtr<ResourceCache> cache_;
};
\endcode

Before the actual HelloWorld implementation, we define WinMain.

\code
int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE prevInstance, PSTR cmdLine, int showCmd)
{
    SharedPtr<Context> context(new Context());
    SharedPtr<Engine> engine(new Engine(context));
    engine->Initialize("HelloWorld", "HelloWorld.log", ParseArguments(GetCommandLineW()));

    SharedPtr<HelloWorld> helloWorld(new HelloWorld(context));
    helloWorld->Start();
    while (!engine->IsExiting())
        engine->RunFrame();

    return 0;
}
\endcode

First, we create the Context object, which holds all subsystems and object factories, and keeps track of event senders and receivers. All Object subclasses need to be supplied a pointer to that context. When using an object factory (such as when creating components) that is automatic, but when creating objects manually, the pointer also needs to be passed manually.

With the context at hand, we create the Engine and initialize it. The arguments for the \ref Engine::Initialize "Initialize()" function are the initial window title, the log file name, and command line parameters, which are parsed using the ParseArguments() helper function.

After this, we instantiate the HelloWorld object, call its Start() function, and run the main loop until Engine tells that we should exit. The shared pointers will take care of deleting the objects in the correct order; the Context will be the last to be destroyed.

Now we can start implementing HelloWorld. 

\code
OBJECTTYPESTATIC(HelloWorld);

HelloWorld::HelloWorld(Context* context) :
    Object(context),
    cache_(GetSubsystem<ResourceCache>())
{
}
\endcode

Note the OBJECTTYPESTATIC(className) macro, which creates the static type name and type name hash for object type identification. For each OBJECT macro, a matching OBJECTTYPESTATIC must appear in a .cpp file. 

During construction, we only store the ResourceCache subsystem pointer for later access.

In the Start() function the Scene will be created:

\code
void HelloWorld::Start()
{
    helloScene_ = new Scene(context_);

    CreateObjects();
    CreateText();
    SubscribeToEvents();
}
\endcode

Like in the script example, CreateObjects() does the actual scene object creation and defines the viewport. 

\code
void HelloWorld::CreateObjects()
{
    helloScene_->CreateComponent<Octree>();

    Node* objectNode = helloScene_->CreateChild();
    Node* lightNode = helloScene_->CreateChild();
    Node* cameraNode = helloScene_->CreateChild();

    StaticModel* object = objectNode->CreateComponent<StaticModel>();
    object->SetModel(cache_->GetResource<Model>("Models/Mushroom.mdl"));
    object->SetMaterial(cache_->GetResource<Material>("Materials/Mushroom.xml"));

    Light* light = lightNode->CreateComponent<Light>();
    light->SetLightType(LIGHT_DIRECTIONAL);
    lightNode->SetDirection(Vector3(-1.0f, -1.0f, -1.0f));

    Camera* camera = cameraNode->CreateComponent<Camera>();
    cameraNode->SetPosition(Vector3(0.0f, 0.3f, -3.0f));

    GetSubsystem<Renderer>()->SetViewport(0, new Viewport(helloScene_, camera));
}
\endcode

Unlike in script, where properties were used to set the component values and scene node transforms, here we must use setter functions instead. Also, whereas strings were used in script to identify the components to create, here it is most convenient to use the template form of \ref Node::CreateComponent "CreateComponent()":

The text overlay creation is next. Again, setters are used throughout:

\code
void HelloWorld::CreateText()
{
    SharedPtr<Text> helloText(new Text(context_));
    helloText->SetFont(cache_->GetResource<Font>("Fonts/Anonymous Pro.ttf"), 30);
    helloText->SetText("Hello World from Urho3D");
    helloText->SetColor(Color(0.0f, 1.0f, 0.0f));
    helloText->SetHorizontalAlignment(HA_CENTER);
    helloText->SetVerticalAlignment(VA_CENTER);

    GetSubsystem<UI>()->GetRoot()->AddChild(helloText);
}
\endcode

Finally we get to event subscribing and handling.

\code
void HelloWorld::SubscribeToEvents()
{
    SubscribeToEvent(E_UPDATE, HANDLER(HelloWorld, HandleUpdate));
}
\endcode

The helper macro HANDLER is used to create pointers to the event handler member functions: it takes the class name followed by the function name. Note also that unlike script, where events and event parameters are identified with strings, in C++ precalculated hash constants are used instead. The frame update event is defined in CoreEvents.h.

In C++ the event handler function must always have the signature "void HandleEvent(StringHash eventType, VariantMap& eventData)". Note that when accessing event parameters, the event's name is used as a namespace to prevent name clashes:

\code
void HelloWorld::HandleUpdate(StringHash eventType, VariantMap& eventData)
{
    float timeStep = eventData[Update::P_TIMESTEP].GetFloat();

    if (GetSubsystem<Input>()->GetKeyDown(KEY_ESC))
        GetSubsystem<Engine>()->Exit();
}
\endcode

Now you should be ready to compile HelloWorld.cpp. The resulting executable will be placed in the Bin directory. It should be substantially smaller than Urho3D.exe due to leaving out the scripting functionality.


\page EditorInstructions Editor instructions

The Urho3D scene editor is a script application that can be run with the Urho3D main executable. To start, execute either of these commands: (in the Bin directory) Editor.bat or Urho3D.exe Scripts/Editor.as

Hint: to get some content to look at, run the TestScene example, and press F5. This saves a scene file called Scene.xml into the Data/Scenes subdirectory, which can be loaded in the editor. The NinjaSnowWar scene also exists in the Data/Scenes subdirectory, and the NinjaSnowWar object "prefabs" are in the Data/Objects subdirectory.

\section EditorInstructions_Controls Controls

\verbatim
Left mouse      - Select nodes or drag the node transform gizmo. Hold Shift to 
                  select components instead. Hold Ctrl to multiselect.
Right mouse     - Hold down and move mouse to rotate camera

WSAD or arrows  - Move
Shift+WSAD      - Move faster
Ctrl+1,2,3      - Select manipulation mode: move/rotate/scale
Ctrl+4          - Toggle between world and local axes manipulation
Ctrl+5,6        - Cycle through components to pick: geometries, lights, zones,
                  collision shapes
Ctrl+arrows     - Manipulate node in X & Z directions
Ctrl+pgup/pgdn  - Manipulate node in Y direction
Ctrl+plus/minus - Scale node uniformly (scale mode only)
Ctrl+O          - Open scene
Ctrl+S          - Save scene
Ctrl+Shift+S    - Save scene as
Ctrl+A          - Select/deselect all root level nodes
Ctrl+X,C,V      - Cut/copy/paste node or component
Ctrl+U          - Unparent scene node
Ctrl+H	        - Open the scene hierarchy window
Ctrl+N	        - Open the node / component edit window
Ctrl+P          - Toggle scene update on/off
Ctrl+R          - Reload scene resources
ESC             - Close the file selector or editor settings window
DEL             - Delete node or component
F1              - Toggle console
F2              - Toggle rendering debug geometry
F3              - Toggle physics debug geometry
F4              - Toggle octree debug geometry
\endverbatim

Press right mouse button in the 3D view if you want to defocus the active window without changing the object selection.

\section EditorInstructions_Workflow Workflow

When you start with an empty scene, set the resource path first (%File -> %Set resource path). This is the base directory, under which the subdirectories Models, Materials & Textures will be created as you import assets.

Scenes should be saved either into this base directory, or into its immediate subdirectory, named for example Scenes or Levels. When loading a scene, the resource path will be set automatically.

Check the Editor settings window so that the camera parameters match the size of the objects you are using.

The editor settings will be saved on exit to a file Urho3D\Editor\Config.xml in the My Documents directory. Delete this file if you want to revert the settings to defaults.

\section EditorInstructions_Editing Editing

New scene nodes and components are created with the buttons at the bottom of the hierarchy window. Their attributes can then be edited in the node / component edit window. Note that the node transform shown is the local transform (offset from parent.)

%Scene nodes can also be moved/rotated/scaled by Ctrl + arrow keys and Page Up / Page Down. Press Ctrl+1,2,3 to change the manipulation mode, and Ctrl+4 to toggle between world relative and scene node relative movement.

To reparent scene nodes, drag and drop them onto the new parent scene node in the scene hierarchy window. Reparenting should retain the effective world transform, so check afterwards from the component window that the local transform is what you expect it to be. Components can not be dragged between nodes, but can be duplicated with cut/copy/paste operations.

Though Urho3D supports setting a non-identity transform on the root node (scene), it is still best to leave it at identity (position 0, 0, 0, rotation 0, 0, 0, scale 1, 1, 1.)

To create a user variable into the current node, or delete it, type the variable name into the edit field below the node attributes, and press New or Del buttons next to it. The New button will prompt to choose the variable type.

While editing, you can execute script files using the "Run script" item in the %File menu. These are AngelScript files that are executed in immediate mode ie. you do not need to define a function. The editor's scene will be accessible to the script as the global property "scene."

Automatic resource reloading when changed (for example editing a texture in a paint program while the scene editor is running) is currently supported on Windows only. On other platforms you need to manually reload scene resources (Ctrl+R) after editing to make the changes visible.

Components of same type can be multi-edited. Where attribute values differ, the attribute field will be left blank, but editing the attribute will apply the change to all components.

In addition to whole scenes, single scene nodes including all their components and child nodes can be loaded and saved (%File -> Load node, %File -> Save node as.) These can act as "prefabs" for speeding up scene construction. To save a node, it needs first to be selected in the hierarchy window.

Primitive geometries (boxes, spheres, cylinders) can be instantiated from the Create menu. Note that these are just ordinary model files in the Bin/Data/Models directory; their Blender format source files are in the SourceAssets directory.

\section EditorInstructions_Importing Importing

The editor can import models or scenes from all the formats that the Open Asset Import Library supports, see http://assimp.sourceforge.net/main_features_formats.html

%Model and scene import work differently: model import will take everything in the source file (for example a Collada scene), and combine it into a single model, with possibly many subgeometries. %Scene import on the other hand will export each source scene node separately, creating multiple models as necessary.

When a model is imported, it will also be instantiated into the scene as a new scene node with a StaticModel component.

To do the actual importing, the editor will invoke AssetImporter.exe from the same directory as where Urho3D.exe resides, so be sure both are built.

Importing lights is not properly supported yet. Instead, when a scene is imported, a zone for ambient lighting and a single directional light are created, so that you can at least see something.

*/