Summary: Behaviour of hydro/nuclear/solar plants etc doesn't
match documentation
                 Project: Freeciv
            Submitted by: jtn
            Submitted on: Wednesday 14/10/09 at 00:02
                Category: rulesets
                Severity: 3 - Normal
                Priority: 5 - Normal
                  Status: None
             Assigned to: None
        Originator Email: 
             Open/Closed: Open
         Discussion Lock: Any
        Operating System: None
         Planned Release: None



This mainly concerns the Solar Plant in the trunk build, but not entirely.
Sorry there are multiple issues here, but they're related.

How I got into this: with a trunk build, I noticed that my Solar Plant wasn't
eliminating all shield pollution as advertised. I found that my Recycling
Center was inhibiting this effect; selling the latter gave the desired effect
from the former.

Then I dug deeper into the ruleset and found a bunch of what seem to me like
inconsistencies. I don't know what the right answers are here yet, but if
someone can give a consensus I can write patches.

(I was in two minds as to whether to post this here or in the forum. Sorry if
I picked wrong.)

(1) The effect when a Solar Plant is present in a city at the same time as
another pollution-reducing building seems unhelpful. A Solar Plant's
pollution effects are neutralised by the presence of any of a Recycling
Center, Nuclear Plant, Hydro Plant, or the Hoover Dam -- you get the (almost
always, see below) lesser effect of the less advanced building. This is in
contrast to the interaction between Recycling Center and (non-solar) Plants,
where you get the better (66%) effect from the R.C.
I can imagine this being particularly annoying for the Hoover Dam -- if
you've got that wonder, Solar Plants are of no use to you and there's nothing
you can do about it. (Unless that case is a deliberate balancing strategy? If
so, it should be documented, and preferably, starting to build a Solar Plant
should be disallowed.)

(2) More generally, the "priority" of the various plants in effects.ruleset
seems inconsistent. For instance, Hydro Plant "wins" over Power Plant wrt
Output_Bonus, but Power Plant "wins" over Solar Plant.
All the Output_Bonuses are the same, so this has no effect on gameplay, but
if they followed a consistent ordering then is_building_replaced(), and hence
the city dialog, could mark buildings as redundant, which is cosmetic but nice
(it's a reminder that you should consider selling these useless buildings).

The attached patch (for discussion purposes) addresses points (1) and (2) in
the default ruleset, by establishing consistent priority orders:
 - for Output_Bonus, in order of increasing priority: Power Plant; Hydro
Plant; Nuclear Plant; Hoover Dam; Solar Plant.
 - for Pollu_Prod_Pct, in order of increasing priority: Hydro Plant; Nuclear
Plant; Hoover Dam; Recycling Center Solar Plant.

The effect of the latter is that you almost always get the biggest single
pollution bonus of your buildings, but never a cumulative effect.
(If desired, it would be possible to arrange the opposite effect -- not
getting a pollution bonus from a higher tech until you actually get rid of
your dirty, expensive old Power Plant. Hoover Dam would need special
treatment, though, and it's not obvious that it adds to gameplay.)

The patch leaves one lacuna -- if you have a Solar Plant, a Recycling Center,
and only one of Factory and Mfg. Plant, you get 50% pollution bonus from your
Solar Plant rather than the better 66% you could get from your Recycling
Center. I could also fix this, but want to settle point (3) below first.

(3) The help for each Plant claims a single blanket pollution reduction
(e.g., Nuclear Plant "reduces the amount of pollution generated by production
in a city by 50%" and Solar Plant "eliminates all pollution generated by
production in a city"), but in fact you only get the advertised effect when
you have both a Factory and a Mfg. Plant -- when you have only one, you get
half the pollution effect (e.g., 25% for Nuclear Plant). This is particularly
obvious with Solar Plant -- if you only have a Factory, pollution is only
reduced to half, not eliminated.
Is this deliberate? If so, the documentation needs patching; if not, the
(This part also affects S2_1.)


File Attachments:

Date: Wednesday 14/10/09 at 00:02  Name: plant-consistency-trunk.diff  Size:
5kB   By: jtn
Tweak effects.ruleset so that better Plants (etc) have precedence


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