1. Washington University in St. Louis
CSE 565 – Fall Hardware Acceleration of Gaming Algorithm TNL Ghosting Explained
Abdel Rigumye
Washington University in St. Louis
Copyright 2005

2. Torque Network Library Ghosting Overview
Torque Network Library (TNL) Uses Ghosting as a means of transferring Object State from Server to Client
Entire Object State sent only once.
Subsequently only changes in object state transferred from server to client
TNL goes through great lengths to minimize BW

3. TNL Connection Establishment Creates Ghost Array
On both the Client & Server every entry initially zeroed out
client sends connection request packet to server
server sends connection response: client ID & puzzle
Client
Server
Connection
Client Proxy
Event List
Ghost Array
Connection
Client Proxy
Event List
Ghost Array
Client sends puzzle solution & client ID
send notice of success

4. Population of Ghost Array
Whenever Server ghosts object for first time
GhostID appears in the packet
Client uses the GhostID to create appropriate object
The Ghosted object is stored in position in Ghost Array indexed by CID
Client Side Ghost Array
8 bits
Kill Ghost Flag
Ghost Object Flag
MyScope_Valid
IdSize
GostID
CID
Ghost Object 1
Ghost Params
CID
Ghost Object 2
Ghost Params

5. Problem – Same as string Table
Because Monitor sits between client and server must
Approach I: maintain a copy of client’s Ghost Array
Approach II: modify the TNL packet so GhostID always transmitted
Ghost
Array
Ghost
Array
Ghost
Array
FPX
Network
Network
Game Server
Client

6. Modified TNL Packet GhostID always transmitted in Position Shown
Added Extra Flag to tell HW when we are Ghosting object for the first time
When Flag = 1 expect additional 5 bit GhostID2
When Flag = 0 continue reading GhostParams
GhostID1 equal to GhostID2
MyScope_Valid
IdSize
Ghost Object Flag
CID
Kill Ghost Flag
GostID1
Ghost Params
Ghost Object 1
Ghost Object 2
8 bits
GostID2
First Time Ghosted Flag

7. Parsing TNL Ghost Data Notify is a Connection Oriented Protocol
To implement Ghost Processor for MP1_partIII parse fields of Ghost Data section to obtain GhostID
Look at the packUpdate and unpackUpdate functions associated with the Ghosts
Ghost ID = 19 is a Ship ghostable object
Look at Ship:unpackUpdate and Ship::packUpdate functions

8. Eg: GoalZone::packUpdate
Notify is a Connection Oriented Protocol
Eg: GoalZone::packUpdate
U32 GoalZone::packUpdate {
if(stream->writeFlag(updateMask & InitialMask))
stream->writeEnum(mPolyBounds.size(), MaxPoints);
for(S32 i = 0; i < mPolyBounds.size(); i++)
stream->write(mPolyBounds[i].x);
stream->write(mPolyBounds[i].y); }
if(stream->writeFlag(updateMask & TeamMask))
stream->write(mTeam);
return 0;