清源游民　gameogre@gmail.com
日志系統：
日志記錄了基于ogre的程序每次運行時的所有事件，系統初始化，狀態，性能信息。輸出的內容被放在磁盤文件上，文件缺省名是ogre.log。也可以手動顯示創建日志系統,這需要在創建Root對象之前實施。
// create an instance of LogManager prior to using LogManager::getSingleton()
LogManager* logMgr = new LogManager;
Log *log = LogManager::getSingleton().createLog("mylog.log", true, true, false);
// third param is not used since we already created a log in the previous step
Root *root = new Root("", "");
可以用Ogre LogManager注冊一個Log Listener, 以任何方式重定向log data。可以用這種方式來屏蔽任何日志信息。然后還一個更簡單的方法達到上述目的：在實例化Root之前，當實例化一個LogManager后，不調用createLog()方法。
以下是實現日志信息截流的代碼片斷：
class MyLogListener : public LogListener
{
public:
void write (const String& name, const String& message,
LogMessageLevel level, bool maskDebug)
{
// redirect log output here as needed
};
MyLogListener *myListener = new MyLogListener;
// this is the same as calling LogManager::getSingletonPtr() after the
// LogManager has first been instanced; the same pointer value is returned
LogManager *logMgr = new LogManager;
LogMgr->addListener(myListener);
logMgr->createLog("mylog.log", true, false, true);
logMgr->setLogDetail(LL_NORMAL);
Root *root = new Root("", "", "mylog.log");
Ogre手動初始化
int main(int argc, char *argv[])
{

?// tell Root not to load from any plugins or settings file
?Root *root = new Root("", "");

?// Load feature plugins. Scene managers will register
?// themselves for all scene types they support
?root->loadPlugin("Plugin_CgProgramManager");
?root->loadPlugin("Plugin_OctreeSceneManager");

?// load rendersystem plugin(s). The order is important in that GL
?// should be available on on platforms, while D3D9 would be available
?// only on Windows -- the try/catch will intercept the exception in this
?// case where D3D9 is not available and continue gracefully.
?try {
??root->loadPlugin("RenderSystem_GL");
??root->loadPlugin("RenderSystem_Direct3D9");
?}
?catch (...) {}

?try {
??// We'll simulate the selection of a rendersystem on an arbirtary basis; normally
??// you would have your own code to present the user with options and select the
??// rendersystem on that basis. Since a GUI is beyond the scope of this example, we'll
??// just assume the user selected OpenGL.
??RenderSystemList *rList = root->getAvailableRenderers();
??RenderSystemList::iterator it = rList->begin();
??RenderSystem *rSys = 0;

??while (it != rList->end()) {
???
???rSys = *(it++);
???if (rSys->getName().find("OpenGL")) {
???
????root->setRenderSystem(rSys);
????break;
???}
??}

??// check to see if a render system was selected; if we reached the end of the list
??// without selecting a render system then none was found.
??if (rSys == 0) {
???delete root;
???std::cerr << "No RenderSystem available, exiting..." << std::endl;
???return -1;
??}

??// We can initialize Root here if we want. "false" tells Root NOT to create
??// a render window for us
??root->initialise(false);

??// set up the render window with all default params
??RenderWindow *window = rSys->createRenderWindow(
???"Manual Ogre Window",?// window title
???800,?????// window width, in pixels
???600,?????// window height, in pixels
???false,?????// fullscreen or not
???0);??????// use defaults for all other values

??// from here you can set up your camera and viewports as normal
??// get a pointer to the default base scene manager -- sufficient for our purposes
??SceneManager *sceneMgr = root->createSceneManager(ST_GENERIC);

??// create a single camera, and a viewport that takes up the whole window (default behavior)
??Camera *camera = sceneMgr->createCamera("MainCam");
??Viewport *vp = window->addViewport(camera);
??vp->setDimensions(0.0f, 0.0f, 1.0f, 1.0f);
??camera->setAspectRatio((float)vp->getActualWidth() / (float) vp->getActualHeight());
??camera->setFarClipDistance(1000.0f);
??camera->setNearClipDistance(5.0f);

??// Run the manual render loop. Since we are not using a frame listener in this case, we
??// will count to 15 seconds and then instead of exiting, we'll change the render window settings
??// and re-initialize it.
??bool renderLoop = true;
??Timer *timer = Ogre::PlatformManager::getSingleton().createTimer();
??timer->reset();
??float s = 0.0f;

??while (renderLoop && window->isActive()) {

???renderLoop = root->renderOneFrame();

???// accumulate total elapsed time
???s += (float)timer->getMilliseconds() / 1000.0f;

???// if greater than 15 seconds, break out of the loop
???if (s >= 15.0f)
????renderLoop = false;

???// we must call the windowing system's message pump each frame to
???// allow Ogre to process messages
???//PlatformManager::getSingleton().messagePump();
??}
?}
?catch (Exception &e) {
??std::cerr << e.getFullDescription() << std::endl;
?}

?delete root;
?return 0;
}

視口
通過視口上的一點與相機的原點產生世界空間中的一條光線
// x and y are in "normalized" (0.0 to 1.0) screen coordinates
Ray getCameraToViewportRay(Real x, Real y) const;

視口,創建多個視口，通過Z序（越高越在上）　確定覆蓋效果，每個視口可以有不同的背景。
// assume window is a valid pointer to an existing render window, and
// a valid pointer to an existing camera instance
Viewport *vpTop, *vpBottom;
// second parameter is z-order, remaining params are position and size,
vpBottom = window->addViewport(camera, 0);
// create a smaller viewport on top, in the center, 25% of main vp size
vpTop = window->addViewport(camera, 1,
0.375f, 0.375f,
0.25, 0.25);
// set the background of the top window to blue (the default is black
// need to set the bottom window explicitly)
vpTop->setBackgroundColour(ColourValue(0.0f, 0.0f, 1.0f));
// an alternate way to set the color is to use the manifest constant
// vpTop->setBackgroundColour(ColourValue::Blue);
在多視口情況下，overlay缺省在每個視口中渲染。可以關掉。Skybox, Shadow也是如此。
vpTop->setOverlaysEnabled(false);
vpTop->setSkiesEnabled(false);
vpTop->setShadowsEnabled(true);