Add DotScene usage scenarios

[sercero]

I had a lot of trouble understanding how to use the Plugin, most of the information is in this thread: https://forums.ogre3d.org/viewtopic.php?t=96069 but it is not clear how to do it the modern way.
Eventually found the code in OgreSceneLoader.cpp, but new users should have an easier time using this important plugin.
If this gets accepted, I will see if the manual can be modified to put an example.

[paroj]

note, I deprecated SceneLoaderManager after improving the Codec API, which it is now duplicating.

typically that nasty Codec::decode call would be encapsulated somewhere (like is the case for Mesh). However, I am not sure where to put it.
SceneManager::setWorldGeometry seems suitable, but it is currently very much tailored to loading BSP "worlds" - whereas you can encapsulated arbitrary chunks of your scene in .scene.

[sercero]

note, I deprecated SceneLoaderManager after improving the Codec API, which it is now duplicating.

typically that nasty Codec::decode call would be encapsulated somewhere (like is the case for Mesh). However, I am not sure where to put it.
SceneManager::setWorldGeometry seems suitable, but it is currently very much tailored to loading BSP "worlds" - whereas you can encapsulated arbitrary chunks of your scene in .scene.

I think the syntaxis should be something like this:

Ogre::DotSceneLoader *loader = new Ogre::DotSceneLoader();
loader->load("level.scene", "ResourceGroup", attachmentNode);

And behind the scenes there is the codec.

That seems to me like the most intuive way to do it...

[sercero]

I just tested the code: Codec::getCodec("scene")->decode(stream, attachmentNode);

With this code I don't need to link against libPlugin_DotScene as you said, but now it is using the Resource Group "General", so I can't specify a resource group for the scene.

[paroj]

it uses ResourceGroupManager::getSingleton().getWorldResourceGroupName() internally

[paroj]

I think the syntaxis should be something like this:

we cannot use the DotSceneLoader type or we would have to link against the plugin.

Also, the user should not care about the format, so both XXX.load("foo.scene") and XXX.load("foo.bsp") could work if the according plugin is present.