History: MadMarx Tutorial 3

Source of version: 9 (current)

!Foreword.
If you prefer tutorials that come with a framework => check the other wiki tutorial series.
If you prefer tutorials that go step by step without a framework => this page should be ok.

I assume you know C++. If not, this tutorial will probably be hard to understand !

This tutorial presents only a few elements of Ogre3D.

You can download the code and media for this tutorial at the bottom of this wiki page.
This little tutorial is an extract of a bigger project which contains more tutorials & helper classes.
This bigger project is avaible there : 
https://sourceforge.net/projects/so3dtools/

Also, make sure you read these tutorials in order!

{maketoc}

!!Tutorial Description
In this program, I create an Ogre RenderWindow. Then I create an empty scene, with a ((-Camera|camera)).
I then add a ((-Viewport|viewport)) to the renderwindow. This ((-Viewport|viewport)) will use the view of the ((-Camera|camera)) to
display the scene.
I chose to create the ((-Viewport|viewport)) so that it will cover 88% of the size of the window.
And I will select a 'kind of pink' background color for that ((-Viewport|viewport)).
As a consequence you should see a window with a 'centered pink sub-rectangle'.
The color of the pixels that are outside the ((-Viewport|viewport)) is undefined and depends on the graphic card driver.
You might even see ghosts of previous program in it.

I have put my whole ogre initialisation into that class.

{CODE(wrap="1",colors="c++")} 
¤	OgreEasy::SimpleOgreInit lOgreInit;
	
	if(!lOgreInit.initOgre())
	{
		std::cout<<"Impossible to init Ogre correctly."<<std::endl;
		return;
	}
{CODE} 
I prefer to be able to access my variables directly.

{CODE(wrap="1",colors="c++")} 
¤	Ogre::Root* lRoot = lOgreInit.mRoot.get();
	Ogre::RenderWindow* lWindow = lOgreInit.mWindow;
{CODE} 
I create a scenemanager. This is like a 'Scene', in which I can put lights, 3d objects, etc...
The scenemanager contains an arborescent graph of 'SceneNodes'. To manage elements of the scene,
I will create SceneNodes in the ((-SceneManager|SceneManager)), and attach the elements to the scenenodes.
First parameter : I select a kind of ((-SceneManager|SceneManager)). This may have a huge impact on performance.
Depending on your scene, some are better than other. The default one does no optimization at all.
Second parameter : I give a name to the scenemanager.
Note : It is easy to have more than one scenemanager (If you got 2 different scenes for example).

{CODE(wrap="1",colors="c++")} 
¤	Ogre::SceneManager* lScene = lRoot->createSceneManager(Ogre::ST_GENERIC, "MyFirstSceneManager");
{CODE} 
The 'root ((-SceneNode|SceneNode))' is the only scenenode at the beginning in the ((-SceneManager|SceneManager)).
The SceneNodes can be seen as 'transformation' containers <=> it contains scale/position/rotation
of the objects. There is only 1 root scenenode, and all other scenenode are
its direct or indirect children.

{CODE(wrap="1",colors="c++")} 
¤	Ogre::SceneNode* lRootSceneNode = lScene->getRootSceneNode();
{CODE} 
I create a ((-Camera|camera)). It represent a 'point of view' in the scene.

{CODE(wrap="1",colors="c++")} 
¤	Ogre::Camera* lCamera = lScene->createCamera("MyFirstCamera");
{CODE} 
I attach the ((-Camera|camera)) to a new ((-SceneNode|SceneNode)). It will be easier then to move it in the scene.

{CODE(wrap="1",colors="c++")} 
¤	Ogre::SceneNode* lCameraNode = lRootSceneNode->createChildSceneNode("MyFirstCameraNode");
	lCameraNode->attachObject(lCamera);
{CODE} 
We create a ((-Viewport|viewport)) on a part of the window.
A ((-Viewport|viewport)) is the link between 1 ((-Camera|camera)) and 1 drawing surface (here the window).
I can then call 'update();' on it to make it draw the Scene from the ((-Camera|camera)).
You can have several viewports on 1 window.
Check API for details on parameters.

{CODE(wrap="1",colors="c++")} 
¤	float lViewportWidth = 0.88f;
	float lViewportHeight = 0.88f;
	float lViewportLeft	= (1.0f - lViewportWidth) * 0.5f;
	float lViewportTop = (1.0f - lViewportHeight) * 0.5f;
	unsigned short lMainViewportZOrder = 100;
	Ogre::Viewport * vp = lWindow->addViewport(lCamera, lMainViewportZOrder, lViewportLeft, lViewportTop, lViewportWidth, lViewportHeight);
{CODE} 
I want the ((-Viewport|viewport)) to draw the scene automatically
when I will call lWindow->update();

{CODE(wrap="1",colors="c++")} 
¤	vp->setAutoUpdated(true);
{CODE} 
I choose a color for this ((-Viewport|viewport)).
I prefer to have a bright color, to detect holes in geometry etc...

{CODE(wrap="1",colors="c++")} 
¤	vp->setBackgroundColour(Ogre::ColourValue(1,0,1));
{CODE} 
I choose the visual ratio of the ((-Camera|camera)). To make it looks real, I want it the same as the ((-Viewport|viewport)).

{CODE(wrap="1",colors="c++")} 
¤	float ratio = float(vp->getActualWidth()) / float(vp->getActualHeight());
	lCamera->setAspectRatio(ratio);
{CODE} 
I choose the clipping far& near planes. if far/near>2000, you can get z buffer problem.
eg : far/near = 10000/5 = 2000 . it's ok.
If (far/near)>2000 then you will likely get 'z fighting' issues.

{CODE(wrap="1",colors="c++")} 
¤	lCamera->setNearClipDistance(1.5f);
	lCamera->setFarClipDistance(3000.0f); 
{CODE} 
I want my window to be active

{CODE(wrap="1",colors="c++")} 
¤	lWindow->setActive(true);
{CODE} 
I want to update myself the content of the window, not automatically.

{CODE(wrap="1",colors="c++")} 
¤	lWindow->setAutoUpdated(false);
{CODE} 
cleaning of windows events managed by Ogre::WindowEventUtilities::...
I call it after a 'pause in window updating', in order to maintain smoothness.
Explanation : if you clicked 2000 times when the windows was being created, there are
at least 2000 messages created by the OS to listen to. This is made to clean them.

{CODE(wrap="1",colors="c++")} 
¤	lRoot->clearEventTimes();
{CODE} 
I wait until the window is closed.
The "message pump" thing is something you will see in most GUI application.
It allow the binding of messages between the application and the OS.
These messages are most of the time : keystroke, mouse moved, ... or window closed.
If I don't do this, the message are never caught, and the window won't close.

{CODE(wrap="1",colors="c++")} 
¤	while(!lOgreInit.mWindow->isClosed())
	{
{CODE} 
Drawings
the window update its content.
each ((-Viewport|viewport)) that is 'autoupdated' will be redrawn now,
in order given by its z-order.

{CODE(wrap="1",colors="c++")} 
¤		lWindow->update(false);
{CODE} 
The drawn surface is then shown on the screen
(google "double buffering" if you want more details).
I always use vertical synchro.

{CODE(wrap="1",colors="c++")} 
¤		bool lVerticalSynchro = true;
		lWindow->swapBuffers(lVerticalSynchro);
{CODE} 
This update some internal counters and listeners.
Each render surface (window/rtt/mrt) that is 'auto-updated' has got its 'update' function called.

{CODE(wrap="1",colors="c++")} 
¤		lRoot->renderOneFrame();
		
		Ogre::WindowEventUtilities::messagePump();
	}
	return;
{CODE} 

! main.cpp 
{CODE(wrap="1",colors="c++")} 
// In this program, I create an Ogre RenderWindow. Then I create an empty scene, with a camera.
// I then add a viewport to the renderwindow. This viewport will use the view of the camera to
// display the scene.
// I chose to create the viewport so that it will cover 88% of the size of the window. 
// And I will select a 'kind of pink' background color for that viewport.
// As a consequence you should see a window with a 'centered pink sub-rectangle'.
// The color of the pixels that are outside the viewport is undefined and depends on the graphic card driver.
// You might even see ghosts of previous program in it.

// I will use std::auto_ptr so I need to include 'memory'. 
// If you don't know std::auto_ptr, you should check some C++ tutorials/lesson on this matter.
#include <memory>
// I will check for std::exception. If you don't know what exception/try/catch means, you should learn C++ first.
#include <exception>

// These are some files that we need to include to use Ogre3D. Note that you can at the beginnings use directly "Ogre.h", to include lots of commonly used classes.
#include "OGRE/OgreRoot.h"
#include "OGRE/OgreRenderWindow.h"
#include "OGRE/OgreWindowEventUtilities.h"

//Here I include my other files, like the one for SimpleOgreInit...
#include "SimpleOgreInit.h"

#include "EasyDefines.h"

// I declare a function in which I will make my whole application.
// This is easy then to add more things later in that function.
// The main will call this function and take care of the global try/catch.
void AnOgreApplication()
{
	// I construct my object that will allow me to initialise Ogre easily.
	OgreEasy::SimpleOgreInit lOgreInit;
	
	if(!lOgreInit.initOgre())
	{
		std::cout<<"Impossible to init Ogre correctly."<<std::endl;
		return;
	}

	//I prefer to be able to access my variables directly.
	Ogre::Root* lRoot = lOgreInit.mRoot.get();
	Ogre::RenderWindow* lWindow = lOgreInit.mWindow;

	// I create a scenemanager. This is like a 'Scene', in which I can put lights, 3d objects, etc...
	// The scenemanager contains an arborescent graph of 'SceneNodes'. To manage elements of the scene,
	// I will create SceneNodes in the SceneManager, and attach the elements to the scenenodes.
	// First parameter : I select a kind of SceneManager. This may have a huge impact on performance.
	// Depending on your scene, some are better than other. The default one does no optimization at all.
	// Second parameter : I give a name to the scenemanager.
	// Note : It is easy to have more than one scenemanager (If you got 2 different scenes for example).
	Ogre::SceneManager* lScene = lRoot->createSceneManager(Ogre::ST_GENERIC, "MyFirstSceneManager");

	// The 'root SceneNode' is the only scenenode at the beginning in the SceneManager.
	// The SceneNodes can be seen as 'transformation' containers <=> it contains scale/position/rotation
	// of the objects. There is only 1 root scenenode, and all other scenenode are 
	// its direct or indirect children.
	Ogre::SceneNode* lRootSceneNode = lScene->getRootSceneNode();

	// I create a camera. It represent a 'point of view' in the scene.
	Ogre::Camera* lCamera = lScene->createCamera("MyFirstCamera");

	// I attach the camera to a new SceneNode. It will be easier then to move it in the scene.
	Ogre::SceneNode* lCameraNode = lRootSceneNode->createChildSceneNode("MyFirstCameraNode");
	lCameraNode->attachObject(lCamera);

	// We create a viewport on a part of the window.
	// A viewport is the link between 1 camera and 1 drawing surface (here the window).
	// I can then call 'update();' on it to make it draw the Scene from the camera.
	// You can have several viewports on 1 window.
	// Check API for details on parameters.
	float lViewportWidth = 0.88f;
	float lViewportHeight = 0.88f;
	float lViewportLeft	= (1.0f - lViewportWidth) * 0.5f;
	float lViewportTop = (1.0f - lViewportHeight) * 0.5f;
	unsigned short lMainViewportZOrder = 100;
	Ogre::Viewport * vp = lWindow->addViewport(lCamera, lMainViewportZOrder, lViewportLeft, lViewportTop, lViewportWidth, lViewportHeight);
	
	// I want the viewport to draw the scene automatically
	// when I will call lWindow->update();
	vp->setAutoUpdated(true);

	// I choose a color for this viewport. 
	// I prefer to have a bright color, to detect holes in geometry etc...
	vp->setBackgroundColour(Ogre::ColourValue(1,0,1));

	// I choose the visual ratio of the camera. To make it looks real, I want it the same as the viewport.
	float ratio = float(vp->getActualWidth()) / float(vp->getActualHeight());
	lCamera->setAspectRatio(ratio);

	// I choose the clipping far& near planes. if far/near>2000, you can get z buffer problem.
	// eg : far/near = 10000/5 = 2000 . it's ok.
	// If (far/near)>2000 then you will likely get 'z fighting' issues.
	lCamera->setNearClipDistance(1.5f);
	lCamera->setFarClipDistance(3000.0f); 

	// I want my window to be active
	lWindow->setActive(true);

	// I want to update myself the content of the window, not automatically.
	lWindow->setAutoUpdated(false);

	// cleaning of windows events managed by Ogre::WindowEventUtilities::...
	// I call it after a 'pause in window updating', in order to maintain smoothness.
	// Explanation : if you clicked 2000 times when the windows was being created, there are 
	// at least 2000 messages created by the OS to listen to. This is made to clean them.
	lRoot->clearEventTimes();

	// I wait until the window is closed.
	// The "message pump" thing is something you will see in most GUI application.
	// It allow the binding of messages between the application and the OS.
	// These messages are most of the time : keystroke, mouse moved, ... or window closed.
	// If I don't do this, the message are never caught, and the window won't close.
	while(!lOgreInit.mWindow->isClosed())
	{
		// Drawings
		// the window update its content.
		// each viewport that is 'autoupdated' will be redrawn now,
		// in order given by its z-order.
		lWindow->update(false);

		// The drawn surface is then shown on the screen
		// (google "double buffering" if you want more details).
		// I always use vertical synchro.
		bool lVerticalSynchro = true;
		lWindow->swapBuffers(lVerticalSynchro);

		// This update some internal counters and listeners.
		// Each render surface (window/rtt/mrt) that is 'auto-updated' has got its 'update' function called.
		lRoot->renderOneFrame();
		
		Ogre::WindowEventUtilities::messagePump();
	}
	return;
}

int main()
{
	try
	{
		AnOgreApplication();
		std::cout<<"end of the program"<<std::endl;
	}catch(Ogre::Exception &e)
	{
		MWARNING("!!!!Ogre::Exception!!!!\n" << e.what());
	}catch(std::exception &e)
	{
		MWARNING("!!!!std::exception!!!!\n"<<e.what());
	}
	OgreEasy::waitForUser();
	return 0;
}

{CODE} 
Link to full source :
http://sourceforge.net/projects/so3dtools/files/Ogre3DWiki/02_EmptyScene.7z/download
History: MadMarx Tutorial 3

Source of version: 9 (current)

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