How to Identify Objects from Client to Server or Server to Client

The purpose of this resource is to show you how to identify objects across client/server boundaries. It is not intended to show you how to select objects, as there are resources for that already.

Objects in Torque Script are represented by IDs. For example, if you select a tree object and echo( %TreeObject ), it will output a number. This works great within the confines of the client or server code you're working in, but if you tried to send this ID to the 'other side' to work on it, you would either get an error, or access the wrong object. This is because each connected client has it's own list of IDs for objects (Though when hosting, you can access both the client and server version of an object directly).

All hope is not lost however, because Torque obviously has a way to identify objects across these boundaries, and it is done with the mighty Ghost Index. Each game connection (one on the clients, and one for each client connected to the server) has a list of objects and their corresponding IDs. These IDs are unique to the game world and do match across client/server boundaries. Accessing and using these IDs is really what this resource is about.

The changes I put in place are simple. Add the following lines to netConnection.cc:

ConsoleMethod( NetConnection, GetGhostIndex, S32, 3, 3, "" )
{
	ShapeBase *pObject;
	if( Sim::findObject( argv[2], pObject ))
		return object->getGhostIndex( pObject );

	return 0;
}

ConsoleMethod( NetConnection, ResolveGhost, S32, 3, 3, "" )
{
	S32 nIndex = dAtoi( argv[2] );
	if( nIndex != -1 )
	{
		NetObject* pObject = NULL;
		if( object->isGhostingTo())
			pObject = object->resolveGhost( nIndex );
		else if( object->isGhostingFrom())
			pObject = object->resolveObjectFromGhostIndex( nIndex );

		return pObject->getId();
	}

	return 0;
}

For some usage examples, i'm going to assume you have a method in place for selecting objects (whether it be with the mouse, or any other way).

Lets say you now have a %TreeObject selected on the client, and you want this %TreeObject to do something on the server (like mount an image, or grow a few feet).

CommandToServer( 'GrowATree', ServerConnection.GetGhostIndex( %TreeObject ));

This will send along the Ghost Index, which can be turned into the local (in this case server) ID with this:

function ServerCmdGrowATree( %Client, %TreeObjectGhostIndex )
{
	%TreeObject = %Client.ResolveGhost( %TreeObjectGhostIndex );

	// Do something with %TreeObject
}

Ok, next we'll assume you have a %TreeObject on the server and you need the client to do something with the object (such as mount an image or make it shake for a few seconds). I'm assuming you have a %Client variable at this point.

CommandToClient( %Client, 'ShakeALeaf', %Client.GetGhostIndex( %TreeObject ));

This will again send along the Ghost Index, which can be turned into the local (in this case client) ID with this:

function ClientCmdShakeALeaf( %TreeObjectGhostIndex )
{
	%TreeObject = ServerConnection.ResolveGhost( %TreeObjectGhostIndex );

	// Do something with %TreeObject
}

Please Note: Ghost Indexes are only available after the object is actually ghosted. If GetGhostIndex returns -1, this could be the reason. For example, I have my project set up so that when I click on a piece of pavement, it builds something on top of it. I now have the newly built object on the server, but the ghost index isn't available yet, so I schedule a timer to wait until it is available to inform the client about it.