[PATCH] Improve the trading mechanism

[wraitii]

Following this ​initial post and this ​revised ideain the forums.

This ticket aims to discuss potential improvements to the trading system, which currently become the main source of resources in the late-game (in team games in particular) and lead to the construction of 100-traders long "lines" of caravans.

This is bad because:

• It just looks bad.
• It's slow on the pathfinder, which is a real problem in MP games
• It makes distance too important, and small distance variations will drastically improve/decrease the efficiency (meaning you get the weird looking "markets at the border of maps" effect)
• It makes it hard to raid trading effectively, you just have too many traders.
• It also means you usually rely on one market, which is unrealistic and (paradoxically with the last point) dangerous.

My "v2" idea, which is implemented in a linked patch, is to shift the resource-creation from traders to markets (or rather entities with a "tradeIncome" component).

Basically, markets now generate income at a fixed rate, depending on the number of trade routes active between them and other markets.

This is further modulated by: -Each trade route has a "base rate bonus" depending on distance, where distance is logarithmic: so it increases drastically until a certain distance and then is only marginally interesting >> reducing the "edge of map" issue -You must garrison workers in your markets to leverage full efficiency. This is done because trading should only become viable when other resources have gotten depleted, or at least far into the game, so it still takes some pop.

I've tried making the interface as clear as currently possible without big changes. The actual implementations details are sorta tricky, but the basic idea is simple: garrison your markets and have more trade routes and more markets.

To make sure that players can't just build more markets, I link markets to CC. Each CC supports one market, and markets must be build not too far away from a CC. This particular link can be discussed, but some limit should be put.

I'm creating a trac ticket because response has been positive overall from many members in the forums, and we do have serious trouble with out current trading model.

[wraitii]

First version (probably not RC)

[wraitii]

Trade Icon used for markets and traders. In To be put in textures/ui/session/icons