Influence 101: A quick and dirty reference to practical influence use
Note: This is all based on my personal work and observations, not any "official" knowledge of the programming behind influence mechanics. It stands well as a working theory, and I haven't seen anything that directly contradicts this, though. Most if not all of this is the same for DL, DA, and TA.
I. Planets
Planets generate influence based on their population, with modifiers for structures on the planet, racial abilities, mined resources, anomalies, etc. These influence points generate a "field" of influence around the planet, which you see as your borders. This field strength degrades with distance from the planet at a linear or near-linear rate. The border appears where your influence field strength drops below one.
II. Starbases
Only mining bases and influence bases generate influence points. Mining bases (on any sort of resource) generate a fixed number of points, so they can't realy affect the surrounding influence fields much. Influence bases generate the same number of points, but the modules you add to them increase the number of points they generate (up to 300%+ depending on what techs you have available). Unlike planets, their influence field degrades with distance squared. This faster drop-off means the area of effect you see around the base is NOT the area the base will affect - it is basically the maximum area the base can affect. At a distance of 8 spaces, the influence from the base is nearly zero. Placing a base to include a planet barely within the area is pointless; the optimal placement for a base is touching the intended target. Even better if you can place it directly between two enemy planets, touching both of them.
III. Border Interactions
As previously stated, your border appears where your field strength is one, but this is only true when the other side of the border is neutral space. The border where two or more influence fields interact is based on a ratio of those fields. In each space, the highest field strength is divided by the sum of all other influence fields, and the border is drawn where this ratio reaches one.
~Professor I. M. Boring~
