Back to RTS4

The previous tutorial series covers most of the basics for an RTS. I probably wont be doing any others for a while as I’d now like to concentrate on RTS4. There has been some quite significant progress made to the project; with the cleaner design from the UnityRTS tutorial series, and the separation of simulation from visuals, the project is much easier to work with now.

Separation of logic

In the UnityRTS projects, although updating happens at a fixed time interval, the coupling of the simulation and visuals makes it difficult to have simulations running in the background and ties the game more closely to the Unity engine (which with Unreal looking so nice, I want to avoid). These two functions are now separate, and each client now runs two simulations concurrently; one for the last known server state, and one for the clients visuals. Each network message is first run on the server, if it is prior to the clients visuals simulation time, the client sim is synced to the servers sim, and then rolled forward to the correct client time. This gives clients no lag while still minimising network bandwidth. As the visuals are separate to these simulations, they can smoothly interpolate whenever the client simulates incorrectly.


The decoupling of the simulation from the Unity visuals means that entities can no longer be described by components on a prefab. To replace and extend this system, each entity now has a prototype object, which calculates any stateless properties (its max health, build time, etc.). Getting a field is not as simple as looking it up by name; Prototypes have a list of technologies which can be enabled or disabled which augment fields, enable / disable components, and even enable / disable other technologies (both for just this entity, or for all entities owned by the player).

These toggleable technologies mean that entities can very simply support buffs and debuffs, by for example enabling a SlowPoison technology. The system also handles armoury upgrades by enabling the HardenedShields player-wide. And it can even be used to handle tech unlocks, for example by enabling age2 player-wide, which can in turn augment the villagers Builds list to include Barracks and Farms.

I dont fully understand the effects system in AoM, but this seems more extensible and quite happy at how many common RTS concepts it can support cleanly. None of my previous attempts included anything like this, so its great to finally understand it.

Unity RTS4 Prototypes example code for Villager


With the changes above, multiplayer is now functional. I’m using the RPC support in Unity to send messages (after serialising them to byte arrays) which conveniently handles lobbies and NAT punchthrough for me.


The current version can be played here (with multiplayer disabled at the moment). I also added in the older models instead of boxes.


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