Introduction

As with all tutorials, a Hello World is almost customary. It turns out that the process of create a Hello World application with Ogre without using ExampleRefApplication requires a few more lines of code than one would expect. Here's a simple tutorial for anyone who would like to see some text on screen without using the ExampleRefApplication.

The Main line

This is a standard cross-platform main line that does nothing other than return 0.

#include <Ogre.h>
 #include <OgreTextAreaOverlayElement.h>
 #include <OgreFontManager.h> 
 #include "ExampleFrameListener.h"
 #define FONT_FILE_NAME "solo5.ttf" 
 // save some horizontal space
 using namespace Ogre;
 #if OGRE_PLATFORM == OGRE_PLATFORM_WIN32
 #define FONT_FOLDER "C:\\My\\Font\\Folder"
 #define WIN32_LEAN_AND_MEAN
 #include "windows.h"
 INT WINAPI WinMain( HINSTANCE hInst, HINSTANCE, LPSTR strCmdLine, INT )
 #else
 #define FONT_FOLDER "/usr/share/ogrenew/Samples/Media/fonts"
 int main(int argc, char **argv)
 #endif 
 {
    return 0;
 }

Initialize Ogre

Now we do the most basic Ogre initialization. The basic steps are:

1. Instantiate Root object
2. Show the config dialog to select a renderer
3. Initialize the Root object without creating a full screen window
4. Create a small RenderWindow
5. Create a generic scene manager
6. Create a Camera for the scene
7. Add a Viewport for the RenderWindow

// create root
 Root *root = new Root();
 // choose renderer
 if(!root->showConfigDialog())
 {
     return 0;
 }
 // initialise root
 root->initialise(false);
 // create main window
 RenderWindow *renderWindow = root->createRenderWindow("Main",320,240,false);
 // create the scene
 SceneManager *sceneMgr = root->createSceneManager(Ogre::ST_GENERIC);
 // add a camera
 Camera *mainCam = sceneMgr->createCamera("MainCam");
 // add viewport
 Viewport *vp = renderWindow->addViewport(mainCam);

Creating a Font resource

Here we need to load the font file into the font manager. Here are the basic steps

1. Get the ResourceGroupManager
2. Add the folder that contains the .ttf file as a resouce location of type 'FileSystem'
3. Get the FontManager
4. Use the FontManager to create a resource and give it a name
5. Set the font parameters
6. Load the font resource

// get the resource manager
 ResourceGroupManager &resGroupMgr = ResourceGroupManager::getSingleton();
 // tell it to look at this location
 resGroupMgr.addResourceLocation(FONT_FOLDER, "FileSystem");
 // get the font manager
 FontManager &fontMgr = FontManager::getSingleton();
 // create a font resource
 ResourcePtr font = fontMgr.create("MyFont","General");
 // set as truetype
 font->setParameter("type","truetype");
 // set the .ttf file name
 font->setParameter("source",FONT_FILE_NAME);
 // set the size
 font->setParameter("size","26");
 // set the dpi
 font->setParameter("resolution","96");
 // load the ttf
 font->load();

Create the TextAreaOverlayElement

Here we need to create TextAreaOverlayElement and render it on our window. Here are the basic steps:

1. Create a Panel and set its position and size
2. Create a TextAreaOverlayElement and set its position, size, caption and font name
3. Add the TextAreaOverlayElement to the Panel as child
4. Create an Overlay and add the Panel to the just created Overlay

// get the overlay manager
 OverlayManager& overlayMgr = OverlayManager::getSingleton();

Here we create a panel and set its position and size.

// Create a panel
 Ogre::OverlayContainer* panel = static_cast<OverlayContainer*>(
    overlayMgr.createOverlayElement("Panel", "PanelName"));
 panel->setMetricsMode(Ogre::GMM_PIXELS);
 panel->setPosition(10, 10);
 panel->setDimensions(300, 120);

Here we create a TextAreaOverlayElement and initialize its

• Position
• Size
• Font and Font Size
• Caption

And finally add the text area to the created panel

// Create a text area
 TextAreaOverlayElement* textArea = static_cast<TextAreaOverlayElement*>(
    overlayMgr.createOverlayElement("TextArea", "TextAreaName"));
 textArea->setMetricsMode(Ogre::GMM_PIXELS);
 textArea->setPosition(0, 0);
 textArea->setDimensions(300, 120);
 textArea->setCharHeight(26);
 // set the font name to the font resource that you just created.
 textArea->setFontName("MyFont");
 // say something
 textArea->setCaption("Hello, World!");

Here we create an Overlay to display the panel

// Create an overlay, and add the panel
 Ogre::Overlay* overlay = overlayMgr.create("OverlayName");
 overlay->add2D(panel);

We have to add the text area to the panel _after_ adding the panel to an overlay to avoid a segfault.

// Add the text area to the panel
 panel->addChild(textArea);

And display our overlay.

// Show the overlay
 overlay->show();

Setup the FrameListener and Hello World

The only thing left to do is to setup the nice frame listener
that will exit the main loop on ESC button or window close event.

Notice: We use the ExampleFrameListener class as a placeholder here before we have a lower level implementation of a frame listener.

// setup frame listener
 ExampleFrameListener *frameListener= new ExampleFrameListener(renderWindow, mainCam);
 frameListener->showDebugOverlay(false);
 root->addFrameListener(frameListener);

After that we should start rendering.

// start rendering
 root->startRendering();

Compile and run the project. The result is a tiny window like this, saying hello to the world: