ORIGINAL: Lobster
Yeah he has mentioned it a time or two.
OK, well here's what I can remember of how I thought this should work out:
First off, each supply point would have a capacity- I'll call it tons for the sake of simplicity but it could be expressed in a different way- and each unit would have a consumption: how many tons supply to recover 1 point of supply. This is reasonably easy to build up from equipment pieces just like the unit weight; I would make it a function of AP+AT+AA strength, the "weight" of the equipment and whether it acts as transport or not (so that 1 "TOAW truck" consumes more fuel than 1 TOAW armoured car of a similar weight)
Then, each hex would have a carrying capacity: how many tons can pass through here per turn? That depends on the scales, what kind of terrain is in the hex, the interdiction rate and a force-specific variable set by the designer. The Supply Radius variable is co-opted into how far forward supply can move in a single turn. The player could designate forward supply dumps which can both receive and deliver supply.
The really hard part would be the calculation. First, all units need to be assigned to a supply source. If more than one supply source is in range (according to the supply radius) then the system needs a way of determining which one should deliver supply to that unit. I'd suggest this should be based on formation and under the player's control: each formation has a default supply source; if that's not in range the closest is used (which would not necessarily be the best choice). Then the total supply needs of all units in range are calculated. Assuming they can't be fully met, the game would determine what % of that need can be met, and then assign that evenly across all units in range. i.e. if the total need is 1,000 and the capacity is 100, a unit which needs 10 gets assigned 1.
This allows the game to calculate how much supply is moving through each hex according to this distribution, with supply moving by the shortest route (in terms of movement rate). The game can then identify any hexes which exceed capacity, and do some sort of preliminary search for alternative routes for the excess, but this would not need to be exhaustive as the player can create his own diversions with forward supply dumps. The supply level for units depending on such routes are then pro-rated down again accordingly, with the balance of supply remaining in the supply source to be used on a subsequent turn. Unit movement could also count against the total capacity of hexes for supply purposes for the following turn.
This would cover the basics. If you have units far ahead of your supply sources, you have to establish forward depots or they get nothing. Add more units to a strained sector and everyone gets less supply. If you fall back along your supply line, you'll pick up loads of goodies along the way while the other guy will take a while for supply to "catch up".
There's lots that can be added- the capacity to actually deliver supplies on a given turn, prioritisation of different formations, a map overlay so the player can see what routes on his supply network are under strain and where to prioritise opening new ones, the possibility for forward supply dumps to be captured, supply capacity for anchorages and airfields, a co-operation level for supply points for multi-force scenarios- but these are the main points.
I consider this volume-based approach to be
significantly more important than breaking down supply by different types of consumption, but the latter is a lot easier to code and ideally you'd do both.