Let’s have some fences!

Fences have been long on the game’s todo list. Being a really neat feature described by a single word, it comes with a lot of problems to solve. How does one approaches a feature like that?

First the “wants” had to be outlined. Fences might have a number of variants and uses in the game:

• Short crossable fences can be used to designate grain fields and orchards. Purely aesthetic
• Medium breakable fences. Can be a weak fortification, slowing down enemy advance. Maybe they can also be used to keep the cattle
• Tall tough fences can be a better fortification. More expensive and harder to break
• If we think about it, fences around house building sites are somewhat related too

Next comes the problems and features exploration phase. Here’s a short FAQ I did on fences before starting the work. Each line poses a problem and has a solution below. The FAQ is not final and solutions can be changed to accommodate for unforeseen problems, but for now I’m quite happy to have most of the questions answered:

• How are fence plans placed
  • New plan type. Placed between tiles. One side must be walkable/reachable. Cursor magnets to nearest edge and outlines it.
• How fences get built
  • By builder. He arrives on adjacent tile, digs for a while, waits for timber and hammers the fence in place
• What do fences cost 
  • At least one wood or stone
• On which side of the fence should the builder remain?
  • Let the fence plan direct from which side it gets built
• Do builders walk through fences?
  • Maybe they don’t. Let the player manage the sides from which to build.
  • We could allow Builders to walk through fences. But this would break all the immersion and logic. Unless we show Builder hits a fence several times to remove it, walks though and then builds it back again? Builders do walk through small house plan fences though..
• How fences get demolished?
  • Instantly in a puff of dust
• How fences get destroyed?
  • Adding hp would be complicated. Let it be just a chance-based instant destruction. 
  • Maybe we can have a breaking animation and fence remainders on the ground?
• How tough are the fences?
  • We can “roll dice” each hit. Chance of destruction can be linked with warriors attack.
• How do we discourage extensive fortifications, are they a problem?
  • Likely not. The cost is quite high after all.
• Whose property fences are?
  • Fences belong to a player (so warriors know whose fences to break and whose to walk around)
• How do fences interact with houses?
  • Fences should be allowed to make perpendicular contact with houses
  • Fences could be allowed to go alongside house border later on, but likely it’s not needed
• How to build fenced area for cattle?
  • To become cattle yard it needs to be enclosed
  • Area can be built by builders
• What is a yard?
  • Any enclosed area of size 4+ touching the house (e.g. side). Max size is .. ?
• How do animals appear inside the yard
  • Breeder can bring them from the house
• How do animals disappear from the yard
  • Breeder takes them out
• How does Breeder carry the animal?
  • Animal goes by itself on a whistle?
  • Animal gets “follow” order?
  • Animal is taken into hands? (as in KaM) 
• What if fence gets broken?
  • Yard becomes ordinary terrain
  • Animals can walk away
• What if fence gets restored (or is built around existing animals)
  • Area becomes yard again
  • Breeder can access animals in the yard
• What if player builds several yards
  • If they are accessible by Breeder – he can use them
• What if there are odd units/animals in the yard
  • They remain there, if they can not escape
• How do animals breed?
  • Breeder brings them in
• What do animals eat
  • Grass and grain brought by Breeder
• How do animals grow?
  • Cows/Horses grow +1 for each grain eaten
  • Sheep remain at the same size and just grow more wool
• Do we always need fences 
  • No, if the area is naturally enclosed it should be fine too

This FAQ covered the player-side of things. Having that done the coding could begin. The code was written in a separate SVN branch to allow for easier comparison of before/after and overall changes made.

There was a number of cross-dependent problems in implementing of the fences. Here are some of the solved ones:

• Fence edges block diagonal unit passability across a vertice between tiles (just like trees and such). However a fence has 2 endpoints, so code had to be updated to let 1 object block 2 vertices.
• Fences go along tile edges and thus block unit passability. All the passability/pathfinding methods had to be updated to check the edges between tiles for passability
• Unlike roads and fields, fences need to be built from specified side. Fence plan list had to account for that.
• Enemy fences should be breakable, so the passability for warriors had to “ignore” the fences and still plan paths through them, knowing that warrior will break the fence on approach.
• Breaking enemy fences should not interrupt current warriors order
• Warriors should not break allied fences. Which means the terrain traversability now had to account for player alliances.
• Breaking a fence should take some time (1-3 hits depending on warriors strength). Had to come up with a simpler formula for that
• There needs to be support for different fences (visually and mechanically) at least for mapmakers. Thus the fences are planned to have properties and types.
• Had added dynamic script commands to add or remove a fence.
• Fences had to have player color markings on them. Since terrain render is already overly complex and overlay render caused some Z-fighting bugs, fences had to be made to render via a different approach that allowed for colors.
• Refactorings had to be made along the way to adjoin similar methods encountered throughout the code.

Remaining problems and features:

• Own fences need to be demolishable. There’s still no support for that yet. Not sure if this should be done with a confirmation or not.
• It would be nice to have own and allied fence lines to be permeable without destruction. Should the gates be added, and if yes – that’s another bunch of problems to solve
• It would be nice to have fence breaking animation
• Cattle yards are a whole new can of worms. They will likely be implemented as a separate feature after the fences development is complete.

Fences are available since Alpha r8455. There’s already been some testing going on and a small bunch of bugs fixed.