History: How to use different texture layers for different terrains in a terrain group

void BasicTutorial3::createScene(void)
{
    mCamera->setPosition(Ogre::Vector3(0, 50, 0));
    mCamera->lookAt(Ogre::Vector3(512, 0, 512));
    mCamera->setNearClipDistance(0.1);
    mCamera->setFarClipDistance(50000);

    if (mRoot->getRenderSystem()->getCapabilities()->hasCapability(Ogre::RSC_INFINITE_FAR_PLANE))
    {
        mCamera->setFarClipDistance(0);   // enable infinite far clip distance if we can
    }

// Play with startup Texture Filtering options
// Note: Pressing T on runtime will discarde those settings
//  Ogre::MaterialManager::getSingleton().setDefaultTextureFiltering(Ogre::TFO_ANISOTROPIC);
//  Ogre::MaterialManager::getSingleton().setDefaultAnisotropy(7);

    Ogre::Vector3 lightdir(0.55, -0.3, 0.75);
    lightdir.normalise();

    Ogre::Light* light = mSceneMgr->createLight("tstLight");

    light->setType(Ogre::Light::LT_DIRECTIONAL);
    light->setDirection(lightdir);
    light->setDiffuseColour(Ogre::ColourValue::White);
    light->setSpecularColour(Ogre::ColourValue(0.4, 0.4, 0.4));

    mSceneMgr->setAmbientLight(Ogre::ColourValue(0.2, 0.2, 0.2));



	int terrainResolution = 513;	// the number of verticies on each side of a terrain, must be 2^n+1
	float terrainWorldUnits = 1200.0;

    mTerrainGlobals = OGRE_NEW Ogre::TerrainGlobalOptions();

    mTerrainGroup = OGRE_NEW Ogre::TerrainGroup(	mSceneMgr, 					// the scene manager that will handle the terrains
													Ogre::Terrain::ALIGN_X_Z, // align the terrain along the X-Z plane
													terrainResolution, 		// the number of vertices along the edge of the terrains
													terrainWorldUnits);				// The size of the terrain in world units

    mTerrainGroup->setFilenameConvention(Ogre::String("BasicTutorial3Terrain"), Ogre::String("dat"));
    mTerrainGroup->setOrigin(Ogre::Vector3::ZERO);


    //=========================================================
    // Configure terrain defults.
    //=========================================================

    mTerrainGlobals->setMaxPixelError(8);			// When moving far away from the terrain, the terrain will be approximated with
    												// a lower vertex count.  The higher the maxPixelError, the less vertices will be
													// used when approximating (??)


    mTerrainGlobals->setCompositeMapDistance(500);	// How far away from the terrain do we have to be before the terrain texture
													// gets approximated as one big texture. (??)

    //Important to set these so that the terrain knows what to use for derived (non-realtime) data
    mTerrainGlobals->setLightMapDirection(light->getDerivedDirection());
    mTerrainGlobals->setCompositeMapAmbient(mSceneMgr->getAmbientLight());
    mTerrainGlobals->setCompositeMapDiffuse(light->getDiffuseColour());



    // Create default import settings for all terrains created in the group.  We can change these later for each individual
    // terrain we add.  We will do this later.
    Ogre::Terrain::ImportData& defaultimp = mTerrainGroup->getDefaultImportSettings();

    defaultimp.terrainSize = terrainResolution; // The number of vertices along the edge of the terrains

    defaultimp.worldSize = 1200.0f;				//The size of the terrain in world space units.  Terrains would be 1200m x 1200m in dimensions

    defaultimp.inputScale = 15.0;				//When loading height map data from an image, the height will be multiplied by this factor
    											// we are not loading a height field. Our terrain is goign to be flat for now.

    defaultimp.minBatchSize = 33;				//  I don't know what this means
    defaultimp.maxBatchSize = 129;				//

    //defaultimp.inputBias = 0.1;				// I don't know what this does. (??)


    defaultimp.layerList.resize(3);

    defaultimp.layerList[0].worldSize = 100;	// The number of times you want the texture to repeat.
    defaultimp.layerList[0].textureNames.push_back("dirt_grayrocky_diffusespecular.dds");
    defaultimp.layerList[0].textureNames.push_back("dirt_grayrocky_normalheight.dds");


    defaultimp.layerList[1].worldSize = 1; // The number of times you want the texture to repeat.
    defaultimp.layerList[1].textureNames.push_back("grass_green-01_diffusespecular.dds");
    defaultimp.layerList[1].textureNames.push_back("grass_green-01_normalheight.dds");


    defaultimp.layerList[2].worldSize = 30; // The number of times you want the texture to repeat.
    defaultimp.layerList[2].textureNames.push_back("growth_weirdfungus-03_diffusespecular.dds");
    defaultimp.layerList[2].textureNames.push_back("growth_weirdfungus-03_normalheight.dds");

    //==========================================================


	//==========================================================
	// Define the two terrains in the group we are going to use.
	// These won't be loaded until we call the loadAllTerrains(true) function below
	mTerrainGroup->defineTerrain(0,0,0.0f);		// define a flat terrain of height 0 at the (0,0) location in the terrain group
	mTerrainGroup->defineTerrain(0,1,0.0f);		// define a flat terrain of height 0 at the (0,1) location in the terrain group.
	//==========================================================


    // sync load since we want everything in place when we start
    mTerrainGroup->loadAllTerrains(true);


	// how many layers terrain(0,1) has...it should be 3 because we set the default number of layers to be 3 previously.
	int terrain01_layer_count = mTerrainGroup->getTerrain(0,1)->getLayerCount();

	// Now switch the first two texture layers for terrain(0,1) just so we can see the difference when rendered
	mTerrainGroup->getTerrain(0,1)->setLayerWorldSize(0,100);
	mTerrainGroup->getTerrain(0,1)->setLayerTextureName(0,0,"grass_green-01_diffusespecular.dds"); // Set the first layer to be a grass layer instead of rock
	mTerrainGroup->getTerrain(0,1)->setLayerTextureName(0,1,"grass_green-01_normalheight.dds");

	mTerrainGroup->getTerrain(0,1)->setLayerTextureName(1,0,"dirt_grayrocky_diffusespecular.dds"); // Set the second layer to be a rock layer instead of grass
	mTerrainGroup->getTerrain(0,1)->setLayerTextureName(1,1,"dirt_grayrocky_normalheight.dds");



    mTerrainGroup->freeTemporaryResources();		//I dont konw what temporary resources are (??)

	// Generate FOG.  For some reason the fog is only appearing on the grass terrain, not the rock terrain.
    Ogre::ColourValue fadeColour(0.9, 0.9, 0.9);

    mWindow->getViewport(0)->setBackgroundColour(fadeColour);
    mSceneMgr->setFog(Ogre::FOG_LINEAR, fadeColour, 0.0, 10, 2000.0);


	// Create a sky
    Ogre::Plane plane2;
    plane2.d = 100;
    plane2.normal = Ogre::Vector3::NEGATIVE_UNIT_Y;

    //mSceneMgr->setSkyDome(true, "Examples/CloudySky", 5, 8, 500);
    mSceneMgr->setSkyPlane(true, plane2, "Examples/CloudySky", 500, 20, true, 0.5, 150, 150);
}