Turn-based gaming in Darkwind: War on Wheels

Darkwind: War on Wheels is a turn-based car combat MMORPG set in a post-apocalyptic near future (it is currently the year 2060 in-game, in fact). Some of the most fundamental changes I have made to TGE have been related to turn-based gaming.

Firstly, it has allowed substantial efficiency improvements: clients don't do any physics simulation, for example (apart from limited simulation of their owner's ghost car-see below), and hence can smoothly animate far more vehicles and rigidshapes than would normally be possible with the TGE physics code. The game pauses while players submit their orders, then the server simulates one game-second, and distributes the positions of the vehicles at each of the 32 ticks that make up that second. This also gets around problems where the clientside simulation doesn't agree with serverside simulation (which appears as judder in standard TGE vehicle games). Because it is only handling one simulated second every 15 or 20 real-time seconds, the server can quite happily take a few seconds to do the work, if the environment is very busy.

Overall, the network load is vastly reduced, with non-essential packets such as camera control information not being sent (cameras are purely client-side), and with data about non-realtime objects such as vehicles only sent once per turn. The game's realtime objects are all clientside-only (skies, cameras, emitters). Realtime objects are processed as normal by the client, while non-realtime objects only have their processTick methods invoked when 'darkwind time' is running. Particle emitters are quite interesting because they can be either realtime (e.g. explosions) or non-realtime (e.g. damage smoke, wheel dust), and can also have their lifetimes determined by realtime (as normal) or by 'darkwind time' - so that they exist for a number of turns. Explosions often have both types of emitters - realtime fire and smoke when the explosion occurs, and then darkwind-time smoke that kicks in on the next game second. It's pretty cool spinning the camera around a frozen dustcloud coming from the wheels of a car, or a frozen plume of smoke or flames coming from its engine.



One of the other things that is related to turn-based gameplay is the 'ghost' car: as the player moves the GUI controls that set their orders, their car's anticipated position in one second's time is shown as a ghost. The accuracy of the ghost is related to their character's driving skill and state of health (a number of errors are introduced into the physics calculations that are applied to the ghost car). The ghost car sometimes allows far more impressive (and fun) driving than would be managed in a real-time game: races and deathraces on the very slippy tracks, for example, typically turn into powersliding bonanzas.



Turn based gaming also allows a level of tactical detail that's not possible in, say, RTSs - which often degrade into a 'fastest mouse clicker' competition. In Darkwind, you control the movement and control of several vehicles, each with potentially several characters in, and several guns that are individually targeted and fired. I'll say a bit about the detailed game rules, weapons, and critical hits in a later blog.





Darkwind is a turn-based online MMORPG with many original gameplay elements ... we're currently in open alpha so feel free to drop in! We now have Windows, Linux, and OSX clients up and running..

www.dark-wind.com