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Zone builders are bits of code that allow you to shape the generation of a zone. At the lowest level of detail they are used to place and remove objects from zones; more broadly, they can be used to shape the geometry and encounters that a player runs into in a room.

The game provides a limited suite of generic builders that you may find useful for your mod. In general, if you are making small alterations to a zone you do not need to deal with zone builders. On the other hand, if you're planning to create your own maps with custom procedural generation, you will want to know how to write them by hand.

Introduction

Preamble: example code on this page

This page presents several examples that you can refer to for creating your own zone builders. If you wish to follow along with these examples, you should create a small example mod that starts with the following code:

Worlds.xml

<?xml version="1.0" encoding="utf-8" ?>
<worlds>                                           
  <world Name="ZBWorld" ZoneFactory="ZBWorldFactory" DisplayName="zone builder test world">
    <cell Name="ExampleCell">
      <zone Level="10" x="1" y="1" Name="test zone">
        <!-- Leave empty for now -->
      </zone>
    </cell>
  </world>
</worlds>

ZoneFactories.cs

namespace XRL.World.ZoneFactories {
    public class ZBWorldFactory : IZoneFactory {
        public override bool CanBuildZone(ZoneRequest Request) => false;

        public override Zone BuildZone(ZoneRequest Request) {
            var zone = new Zone(80, 25);
            zone.ZoneID = Request.ZoneID;
            return zone;
        }

        public override void AddBlueprintsFor(ZoneRequest Request) {
            var cb = Blueprint.CellBlueprintsByName["ExampleCell"];
            Request.Blueprints.Add(cb.LevelBlueprint[1, 1, 10]);
        }

        public override void AfterBuildZone(Zone zone, ZoneManager zoneManager) {
            ZoneManager.PaintWalls(zone);
            ZoneManager.PaintWater(zone);
        }
    }
}

This will create a miniature world, ZBWorld, that we will use for testing. To teleport into this world, use the wish goto:ZBWorld.40.12.1.1.10.

Using zone builders

When you enter a new zone, the game uses a zone factory (an implementation of IZoneFactory) to generate your zone, using the zone factory appropriate to the world that you are currently in. It starts with a blank zone and successively triggers whatever builders have been specified for the zone.

Most commonly, these zone builders are specified in Worlds.xml. For example, here's the specification of MoonStairCell (used to generate generic Moon Stair zones):

<cell Name="MoonStairCell" Inherits="DefaultJoppaCell" ApplyTo="TerrainMoonStair">
  <zone Level="5-9" x="0-2" y="0-2" Name="sky above the Moon Stair" IndefiniteArticle="the" AmbientBed="Sounds/Ambiences/amb_bed_moonstair">
    <builder Class="Sky"></builder>
  </zone>
  <zone Level="10" x="0-2" y="0-2" Name="Moon Stair" IndefiniteArticle="the" AmbientBed="Sounds/Ambiences/amb_bed_moonstair">
    <builder Class="MoonStair"></builder>        
    <builder Class="FactionEncounters" Population="GenericFactionPopulation"></builder>
    <music Track="Reflections of Ptoh" />
    <postbuilder Class="ZoneTemplate:MoonStair"></postbuilder>
  </zone>
  <zone Level="11-15" x="0-2" y="0-2" Name="subterranean stair">                            
    <builder Class="MoonStair"></builder>                                                           
    <builder Class="PossibleCryotube"></builder>
    <builder Class="FactionEncounters" Population="GenericFactionPopulation"></builder>
    <music Track="Reflections of Ptoh" />
    <postbuilder Class="ZoneTemplate:MoonStairCaves"></postbuilder>
  </zone>
</cell>

Cell specifications are broken up by X, Y, and Z-levels. Depending on where the player is, they will trigger different builders appropriate to their location.

The other place that zone builders are often added is dynamically during world generation. For example, this is how Oboroqoru, Ape God's lair, goatfolk yurts, and dynamic villages are placed by JoppaWorldBuilder. It is possible, but less common, to dynamically apply zone builders in other parts of the game.

Generic, pre-existing zone builders

The game provides a limited suite of zone builders that are sufficiently generic that they can be easily applied to any zone.

Builder name	Description
AddWidgetBuilder	Adds an object to the (0, 0) cell of a zone. Typically this is a `Widget` object (see `ObjectBlueprints/Widgets.xml`) although in theory it can be anything. An `AddWidgetBuilder` builder is added to the zone whenever you use the `<widget/>` tag in `Worlds.xml`.
Connecter
FactionEncounters	Adds encounters with legendary creatures sampled from a provided table.
MapBuilder	This builder loads a map from a .rpm file. A MapBuilder is implicitly to a zone by the `<map/>` tag in Worlds.xml. For example, the map for the Yd Freehold is added as follows: <map FileName="YdFreehold.rpm" />
Music	Adds a music track to a zone. A Music zone builder is implicitly added by the `<music/>` tag in Worlds.xml. For example, the music for the salt dunes is added with <music Track="MoghrayiRemembrance" />
SolidEarth	Fills the entire map with shale. This is useful when you wish to carve out the geometry of your zone (i.e., specify the empty space rather than specify the filled space).
StairConnector
StairsDown	Adds a set of stairs down to the next Z-level. You can specify X- and Y- coordinates to influence the region in which the stairs are placed.
StairsUp	Adds a set of stairs up to the previous Z-level. You can specify X- and Y- coordinates to influence the region in which the stairs are placed.
TileBuilding

In general, the game's existing zone builders tend to be highly monolithic, so any zone builders not listed above are not recommended for use in creating new types of zones. For new zones modders should favor a more modular architecture.

The ZoneBuilderSandbox interface

ZoneBuilderSandbox is the primary interface for creating new zone builders. Any builders that you add to the game will inherit from this class.

Most zone builders only need to define one method: BuildZone. This method accepts a zone instance, and returns a boolean that signals whether or not subsequent zone builders should also run^[1]. As an example, here is the definition for the SolidEarth zone builder:

namespace XRL.World.ZoneBuilders;

public class SolidEarth
{
    public bool BuildZone(Zone Z)
    {
        for (int i = 0; i < Z.Width; i++)
        {
            for (int j = 0; j < Z.Height; j++)
            {
                Z.GetCell(i, j).Clear();
                Z.GetCell(i, j).AddObject(GameObjectFactory.Factory.CreateObject("Shale"));
            }
        }
        return true;
    }
}

This builder

loops over each cell in the zone (incidentally: nowadays there is a Zone.GetCells method to make this even easier);
clears all objects that are currently in the cell; and
adds a shale object to the cell.

When designing new zone builders, you should (where possible) prefer to create modular zonebuilders that can be easily reused. As a general rule, earlier builders should define coarse-grained detail about a zone such as layout and general geometry. Builders that come later should be focused on adding fine-grained details (e.g. individual rooms and encounters) to the zone.

Helpful utilities

In principle, ZoneBuilderSandbox is all that you need in order to build a zone. In practice, you will want to rely on some other utilities when generating zones. This section will cover some of the most important utilities available to you.

EnsureAllVoidsConnected

ZoneBuilderSandbox includes an EnsureAllVoidsConnected that will create paths between empty spaces in your zone. This is particularly useful when you are carving out your zone from another material.

For example: consider the following zone builder:

namespace XRL.World.ZoneBuilders {
    public class CreateVoids : ZoneBuilderSandbox {
        public bool NoisyPath = true;

        public bool BuildZone(Zone Z) {
            foreach (var cell in Z.GetCells()) {
                if (
                    cell.CosmeticDistanceTo(20, 12) < 4 ||
                    cell.CosmeticDistanceTo(50, 12) < 4
                   )
                    cell.Clear();
            }
            EnsureAllVoidsConnected(Z, pathWithNoise: NoisyPath);
            return true;
        }
    }
}

This will create two pockets of empty space -- one centered at coordinates (20, 12), another centered at coordinates (50, 12) -- and connects them with EnsureAllVoidsConnected. By setting pathWithNoise we can make a somewhat randomized path between these voids.

Starting from the code in the introduction, update your Worlds.xml to include the following:

<!-- ... -->
<zone Level="10" x="1" y="1" Name="test zone">
  <builder Class="SolidEarth" />
  <builder Class="CreateVoids" />
  <widget Blueprint="Grassy" />
</zone>
<!-- ... -->

Here is an example of a zone that gets generated with these builders:

Pathfinding FindPath

If you want to create a path directly between two cells, you can use the FindPath interface (which is also used by creature AI to find the shortest path between two points).

Here is an example of the CreateVoids zone builder from the EnsureAllVoidsConnected example using pathfinding (this time with a straight path between the voids).

using XRL.World.AI.Pathfinding;

namespace XRL.World.ZoneBuilders {
    public class CreateVoids : ZoneBuilderSandbox {
        public bool BuildZone(Zone Z) {
            foreach (var cell in Z.GetCells()) {
                if (
                    cell.CosmeticDistanceTo(20, 12) < 4 ||
                    cell.CosmeticDistanceTo(50, 12) < 4
                   )
                    cell.Clear();
            }

            var path = new FindPath(Z.GetCell(20, 12), Z.GetCell(50, 12));
            foreach (var step in path.Steps)
                step.Clear();

            return true;
        }
    }
}

PlacePopulationInRect

PlacePopulationInRegion

Other utilities

Finally, here is a list of some other less commonly-used utilities that you may nonetheless find helpful for your use case:

Name	Class	Description
ClearRect	ZoneBuilderSandbox	Clears out all of the objects from a rectangle in a given zone.

Creating encounters with zone templates

This article is a stub. You can help Caves of Qud Wiki by expanding it.

Procedural generation