But what I'd like to change is how these effects totaled up. In the game 2 effects of the same type (with values x1,x2) are added: total_effect=x1+x2. Is it possible to change this to a multiplication (total_effect=x1*x2), or is this processed by the game engine?
If you make them multiplicative, you change an overpowered system to be insanely overpowered:
Actually, 4 +50% Production Speed moduled gain you +200% Speed,
Multiplicative its already + 406,75%
Are you sure thats what you want?
If you want them to be stronger, just make a mod with additional modules, or use one of the available ones ...
Yes, if it's possible, than that's realy what I want.
Of course, I can change the values of the modules if they become overpowered.
And do not forget that also the negative effects become more severe. Your example (4*speed-module-3):
+70% energy consumption * 4 = +280% energy consumption in the base game and multiplicative:
(1.7^4-1)*100% = +735.21%
And the effeciency module (the only module with no side-effects) becomes weaker when you place more of them in one entity. For example:
2 efficency module 2 = 2*-40% = -80% in the game, while
multiplicative: (0.6)^2 = 0.36 = -64%