MadMarx Tutorial 6         Basic Light

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!

Tutorial Description

In this program, I add a light to the program.
I display a mesh that use a basic material that use this light.
I also animate a little the scene, by rotating the light between each frame.

After viewport creation

I create a light. The scenemanager will contain it.
I will attach this light to a scenenode, so that I can move it easily.
(This will add 1 transformation matrix, but I prefer to control motion homogeneously for all elements).

¤	Ogre::SceneNode* lLightSceneNode = NULL;
	{
		Ogre::Light* lLight = lScene->createLight();

I can set some attributes of the light.
The basic light type can be :
pointlight (like a candle?)
spotlight (kind of 'conic' light)
directional light (like the sun in an outdoor scene).
Directional light is like parallel rays coming from 1 direction.

¤		lLight->setType(Ogre::Light::LT_DIRECTIONAL);

Here I choose the color of the light.
The diffuse color is the main color of the light.
The specular color is its color when reflected on an imperfect surface.
For example, when my bald head skin reflect the sun, it makes a bright round of specular color.

The final color of an object also depends on its material.
Color values vary between 0.0(minimum) to 1.0 (maximum).

¤		lLight->setDiffuseColour(0.8f, 0.3f, 0.3f); // this will be a red light
		lLight->setSpecularColour(1.0f, 1.0f, 1.0f);// color of 'reflected' light

		lLightSceneNode = lRootSceneNode->createChildSceneNode();
		lLightSceneNode->attachObject(lLight);
	}

I add an ambient color. The ambient color is managed in the scenemanager.
If you want to learn more about ambient/specular/diffuse color, check the 'basic material tutorial'
from this serie.

¤	Ogre::ColourValue lAmbientColour(0.2f, 0.2f, 0.2f, 1.0f);
	lScene->setAmbientLight(lAmbientColour);

Then add a scene to display.

¤	Ogre::String lNameOfResourceGroup = "Mission 1 : Deliver Tom";
	{
		Ogre::ResourceGroupManager& lRgMgr = Ogre::ResourceGroupManager::getSingleton();
		lRgMgr.createResourceGroup(lNameOfResourceGroup);

We say which directories will be loaded by this resourcegroup.
I can add many directories, which will be loaded in same the ORDER.
This ORDER is extremely important : if a material is loaded <i>after</i> a mesh using this material,
this mesh won't be able to find the material during its loading!
I advise you not to use a recursive load (which load the full directory tree).
Seriously, 'recursive loading' often leads to problems.

¤		Ogre::String lDirectoryToLoad = "../../media/mesh";
		bool lIsRecursive = false;
		lRgMgr.addResourceLocation(lDirectoryToLoad, "FileSystem", lNameOfResourceGroup, lIsRecursive);

The function 'initialiseResourceGroup' parses scripts if any in the locations.

¤		lRgMgr.initialiseResourceGroup(lNameOfResourceGroup);

Files that can be loaded are loaded.

¤		lRgMgr.loadResourceGroup(lNameOfResourceGroup);

Now the loaded Mesh is available from its ResourceGroup,
as well as from the Ogre::MeshManager. A shared pointer to
it can be accessed by : Ogre::MeshManager::getSingleton().getByName(name_of_the_mesh);

Now I can create Entities using that mesh.

¤		Ogre::String lNameOfTheMesh = "MonsterHead.mesh";
		int lNumberOfEntities = 5;
		for(int iter = 0; iter < lNumberOfEntities; ++iter)
		{
			Ogre::Entity* lEntity = lScene->createEntity(lNameOfTheMesh);

Now I attach it to a scenenode, so that it becomes present in the scene.

¤			Ogre::SceneNode* lNode = lRootSceneNode->createChildSceneNode();
			lNode->attachObject(lEntity);

I move the SceneNode so that it is visible to the camera.

¤			float lPositionOffset = float(1+ iter * 2) - (float(lNumberOfEntities));
			lPositionOffset = lPositionOffset * 20;
			lNode->translate(lPositionOffset, lPositionOffset, -200.0f);

'BaseWhite' is a material already available.
It is grey / white at light. Since the light is red, the result will be red/rosa.

¤			lEntity->setMaterialName("BaseWhite");
		}
	}

In the while()

I make the light rotate.

¤			Ogre::Degree lAngle(2.5);
			lLightSceneNode->yaw(lAngle);

main.cpp

// In this program, I add a light to the program.
// I display a mesh that use a basic material that use this light.
// I also animate a little the scene, by rotating the light between each frame.

// 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/OgreRenderSystem.h"
#include "OGRE/OgreRenderWindow.h"
#include "OGRE/OgreWindowEventUtilities.h"
#include "OGRE/OgreManualObject.h"
#include "OGRE/OgreEntity.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);

	// I create a light. The scenemanager will contain it.
	// I will attach this light to a scenenode, so that I can move it easily.
	// (This will add 1 transformation matrix, but I prefer to control motion homogeneously for all elements).
	Ogre::SceneNode* lLightSceneNode = NULL;
	{
		Ogre::Light* lLight = lScene->createLight();

		// I can set some attributes of the light.
		// The basic light type can be : 
		//		pointlight (like a candle?)
		//		spotlight (kind of 'conic' light)
		//		directional light (like the sun in an outdoor scene).
		// Directional light is like parallel rays coming from 1 direction.
		lLight->setType(Ogre::Light::LT_DIRECTIONAL);

		// Here I choose the color of the light.
		// The diffuse color is the main color of the light.
		// The specular color is its color when reflected on an imperfect surface.
		// For example, when my bald head skin reflect the sun, it makes a bright round of specular color.
		//
		// The final color of an object also depends on its material.
		// Color values vary between 0.0(minimum) to 1.0 (maximum).
		lLight->setDiffuseColour(0.8f, 0.3f, 0.3f); // this will be a red light
		lLight->setSpecularColour(1.0f, 1.0f, 1.0f);// color of 'reflected' light

		lLightSceneNode = lRootSceneNode->createChildSceneNode();
		lLightSceneNode->attachObject(lLight);
	}

	// I add an ambient color. The ambient color is managed in the scenemanager.
	// If you want to learn more about ambient/specular/diffuse color, check the 'basic material tutorial'
	// from this serie.
	Ogre::ColourValue lAmbientColour(0.2f, 0.2f, 0.2f, 1.0f);
	lScene->setAmbientLight(lAmbientColour);

	// Here I choose a name for a resource group. Then I create it.
	// Often, a resourcegroup is a good way to store the data corresponding
	// to a level in a game.
	Ogre::String lNameOfResourceGroup = "Mission 1 : Deliver Tom";
	{
		Ogre::ResourceGroupManager& lRgMgr = Ogre::ResourceGroupManager::getSingleton();
		lRgMgr.createResourceGroup(lNameOfResourceGroup);

		// We say which directories will be loaded by this resourcegroup.
		// I can add many directories, which will be loaded in same the ORDER.
		// This ORDER is extremely important : if a material is loaded <i>after</i> a mesh using this material,
		// this mesh won't be able to find the material during its loading!
		// I advise you not to use a recursive load (which load the full directory tree). 
		// Seriously, 'recursive loading' often leads to problems.
		Ogre::String lDirectoryToLoad = "../../media/mesh";
		bool lIsRecursive = false;
		lRgMgr.addResourceLocation(lDirectoryToLoad, "FileSystem", lNameOfResourceGroup, lIsRecursive);
		
		// The function 'initialiseResourceGroup' parses scripts if any in the locations.
		lRgMgr.initialiseResourceGroup(lNameOfResourceGroup);

		// Files that can be loaded are loaded.
		lRgMgr.loadResourceGroup(lNameOfResourceGroup);

		// Now the loaded Mesh is available from its ResourceGroup,
		// as well as from the Ogre::MeshManager. A shared pointer to
		// it can be accessed by : Ogre::MeshManager::getSingleton().getByName(name_of_the_mesh);

		// Now I can create Entities using that mesh.
		Ogre::String lNameOfTheMesh = "MonsterHead.mesh";
		int lNumberOfEntities = 5;
		for(int iter = 0; iter < lNumberOfEntities; ++iter)
		{
			Ogre::Entity* lEntity = lScene->createEntity(lNameOfTheMesh);
			// Now I attach it to a scenenode, so that it becomes present in the scene.
			Ogre::SceneNode* lNode = lRootSceneNode->createChildSceneNode();
			lNode->attachObject(lEntity);
			// I move the SceneNode so that it is visible to the camera.
			float lPositionOffset = float(1+ iter * 2) - (float(lNumberOfEntities));
			lPositionOffset = lPositionOffset * 20;
			lNode->translate(lPositionOffset, lPositionOffset, -200.0f);
			
			// 'BaseWhite' is a material already available.
			// It is grey / white at light. Since the light is red, the result will be red/rosa.
			lEntity->setMaterialName("BaseWhite");
		}
	}

	// 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())
	{
		// Here I update the scene between 2 frames.
		{
			// I make the light rotate.
			Ogre::Degree lAngle(2.5);
			lLightSceneNode->yaw(lAngle);
		}

		// 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();
	}

	// Let's cleanup!
	{
		lWindow->removeAllViewports();
	}
	{
		lScene->destroyAllCameras();
		lScene->destroyAllManualObjects();
		lScene->destroyAllEntities();
		lScene->destroyAllLights();
		lRootSceneNode->removeAndDestroyAllChildren();
	}
	{
		Ogre::ResourceGroupManager& lRgMgr = Ogre::ResourceGroupManager::getSingleton();
		lRgMgr.destroyResourceGroup(lNameOfResourceGroup);
	}

	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());
	}
	return 0;
}

Full program sources :
http://sourceforge.net/projects/so3dtools/files/Ogre3DWiki/06_BasicLight.7z/download