Building Interior Spaces

Interior spaces (dungeons, buildings, FPS levels) are defined by enclosed areas connected by passages. The Interior module provides stamps for designing these efficiently.

Importing

open Mibo.Layout3D
open Mibo.Layout3D.Interior

Understanding Directions

The DoorSide type specifies which face to operate on:

type DoorSide =
  | North  // Front face (max Z)
  | South  // Back face (min Z)
  | East   // Right face (max X)
  | West   // Left face (min X)

Core Interior Patterns

Basic Room

Every interior level starts with rooms:

let singleRoom =
    CellGrid3D.create 20 5 20 (Vector3(2f, 2f, 2f)) Vector3.Zero
        |> Layout3D.run (fun section ->
            section
            |> Interior.room 12 4 12 FloorCell WallCell CeilingCell
            |> Layout3D.section 6 2 (Layout3D.set 0 0 0 ChestCell)
        )

Connecting Rooms with Corridors

Corridors connect spaces. Use X-aligned for east-west, Z-aligned for north-south:

let connectedRooms =
    section
    // Room 1 (spawn)
    |> Layout3D.section 0 0 0 (Interior.room 10 4 10 FloorCell WallCell CeilingCell)
    |> Layout3D.section 5 2 0 (Layout3D.set 0 0 0 SpawnCell)
    
    // Corridor to Room 2 (east)
    |> Interior.doorway East 2 3
    |> Layout3D.section 10 0 3 (Interior.corridorX 8 2 3 FloorCell WallCell CeilingCell)
    
    // Room 2 (encounter)
    |> Interior.doorway West 2 3
    |> Layout3D.section 18 0 0 (Interior.room 8 4 8 FloorCell WallCell CeilingCell)
    |> Layout3D.section 22 2 0 (Layout3D.set 0 0 0 EnemyCell)

Door placement tip: When using doorway, the corridor and room Y positions must align. A doorway at Y=0 connects to a corridor starting at Y=1 (door height is 3, so doorway spans Y=1,2,3).

Multi-Exit Hubs

Central rooms connecting multiple areas:

let hubRoom =
    section
    |> Interior.room 14 4 14 FloorCell WallCell CeilingCell
    
    // Four exits
    |> Interior.doorway North 2 3  // Exit to north area
    |> Interior.doorway South 2 3  // Exit to south area
    |> Interior.doorway East 2 3   // Exit to east area
    |> Interior.doorway West 2 3   // Exit to west area
    
    // Central marker
    |> Layout3D.center 1 1 1 (Layout3D.set 0 0 0 HubIconCell)

Enclosed vs Open-Top Rooms

Use fully enclosed rooms for most interiors, open-top for exterior or rooftop areas:

let mixedRooms =
    section
    // Fully enclosed indoor room
    |> Layout3D.section 0 0 0 (Interior.room 10 4 10 FloorCell WallCell CeilingCell)
    
    // Open-top area (patio, rooftop, exterior room)
    |> Layout3D.section 15 0 0 (Interior.openRoom 8 2 8 FloorCell WallCell)

Adding Architectural Details

Windows

Windows break up wall surfaces and provide visual interest:

let roomWithWindows =
    section
    |> Interior.room 12 5 12 FloorCell WallCell CeilingCell
    
    // North wall windows
    |> Interior.window North 4 3 2  // Width=4, Height=3, Sill=2
    |> Interior.window North 4 3 2  // Second window (same pattern)
    
    // East wall window
    |> Interior.window East 3 3 2

Window design: - windowWidth: 2-4 cells for standard windows - windowHeight: 2-3 cells for vertical space - sillHeight: 1-2 cells from floor (eye level)

Pillars and Columns

Pillars add vertical interest and cover for gameplay:

let pillaredRoom =
    section
    |> Interior.room 14 5 14 FloorCell WallCell CeilingCell
    
    // Four corner pillars
    |> Layout3D.section 2 0 2 (Interior.pillar 4 PillarBase PillarMid PillarTop)
    |> Layout3D.section 10 0 2 (Interior.pillar 4 PillarBase PillarMid PillarTop)
    |> Layout3D.section 2 0 10 (Interior.pillar 4 PillarBase PillarMid PillarTop)
    |> Layout3D.section 10 0 10 (Interior.pillar 4 PillarBase PillarMid PillarTop)

Pillar usage: - 2-4 tiles high for visual pillars - 4-6 tiles high for climbable columns - Base/middle/top tiles for visual variety

Vertical Shafts

Shafts provide vertical transport (elevators, ladders):

let elevatorShaft =
    section
    |> Interior.shaft 2 2 12 WallCell  // 2x2 shaft, 12 tiles tall

Use shafts between floors with doors opening into them:

let floorWithShaft =
    section
    |> Interior.room 10 5 10 FloorCell WallCell CeilingCell
    
    // Shaft in corner
    |> Layout3D.section 8 0 8 (Interior.shaft 2 2 12 WallCell)
    
    // Door to shaft
    |> Interior.doorway South 2 3

Vertical Traversal

Staircases

Stairs connect floors smoothly:

let stairSection =
    section
    // Lower room
    |> Layout3D.section 0 0 0 (Interior.room 10 4 10 FloorCell WallCell CeilingCell)
    
    // Stairs going up
    |> Interior.doorway East 2 3
    |> Layout3D.section 10 0 3 (Interior.stairs 2 4 4 StairCell)
    
    // Upper room
    |> Interior.doorway West 2 3
    |> Layout3D.section 18 0 0 (Interior.room 8 4 8 FloorCell WallCell CeilingCell)

Stair design: - width: 2-3 cells for player comfort - rise: 4-6 cells for one floor - run: 2-3 cells per step for comfortable climbing

Multi-Level Layouts

Combine rooms, stairs, and balconies:

let multiLevel =
    section
    // Ground floor lobby
    |> Layout3D.section 0 0 0 (Interior.room 12 5 12 FloorCell WallCell CeilingCell)
    |> Interior.doorway East 2 3
    
    // Staircase
    |> Layout3D.section 12 0 4 (Interior.stairs 2 5 5 StairCell)
    
    // Second floor balcony (open-top)
    |> Interior.doorway West 2 3
    |> Layout3D.section 0 5 0 (Interior.openRoom 10 3 12 FloorCell WallCell)
    
    // Windows for exterior view
    |> Interior.window North 4 2 1
    |> Interior.window South 4 2 1

Building Custom Interior Stamps

Encapsulate common room patterns:

module MyInterior =
    /// A room with a door and torches on each wall
    let torchRoom width height depth floor wall ceiling =
        Interior.room width height depth floor wall ceiling
        >> Interior.doorway North 2 3
        >> Interior.doorway South 2 3
        >> Layout3D.set 1 2 0 TorchCell
        >> Layout3D.set (width - 2) 2 0 TorchCell
    
    /// A corridor with torches at both ends
    let litCorridor length width height floor wall ceiling =
        Interior.corridorX length width height floor wall ceiling
        >> Layout3D.set 2 2 0 TorchCell
        >> Layout3D.set (length - 3) 2 0 TorchCell
    
    /// A guard room with weapon racks
    let armory width height depth floor wall ceiling =
        Interior.room width height depth floor wall ceiling
        >> Layout3D.section 1 2 1 (Layout3D.fill 0 0 0 3 1 WeaponRackCell)
        >> Layout3D.section (width - 4) 2 (depth - 2) (Layout3D.fill 0 0 0 3 1 WeaponRackCell)
    
    /// An L-shaped room combination
    let lRoom room1W room1D room2W room2D height floor wall ceiling =
        Layout3D.section 0 0 0 (Interior.room room1W height room1D floor wall ceiling)
        >> Layout3D.section (room1W - 1) 0 0 (Interior.room room2W height room2D floor wall ceiling)
        >> Layout3D.clear (room1W - 1) 0 1 1 height 1

Using Custom Stamps

let customInterior =
    section
    |> Layout3D.section 0 0 0 (MyInterior.torchRoom 12 4 12 FloorCell WallCell CeilingCell)
    |> Layout3D.section 12 0 3 (MyInterior.litCorridor 10 2 3 FloorCell WallCell CeilingCell)
    |> Layout3D.section 22 0 0 (MyInterior.armory 10 5 10 FloorCell WallCell CeilingCell)

Complete FPS Level Example

let levelSection section =
    section
    // === AREA 1: Spawn ===
    // Starting room
    |> Layout3D.section 0 0 0 (Interior.room 10 4 10 FloorCell WallCell CeilingCell)
    |> Interior.doorway East 2 3
    |> Layout3D.section 5 2 0 (Layout3D.set 0 0 0 SpawnCell)
    
    // === AREA 2: Corridor Network ===
    // Main corridor with turns
    |> Layout3D.section 10 0 3 (Interior.corridorX 6 2 3 FloorCell WallCell CeilingCell)
    
    // Side room (ammo pickup)
    |> Layout3D.section 10 0 0 (Interior.room 4 3 4 FloorCell WallCell CeilingCell)
    |> Layout3D.set 12 1 1 AmmoCell
    
    // Continue corridor
    |> Layout3D.section 14 0 3 (Interior.corridorX 6 2 3 FloorCell WallCell CeilingCell)
    
    // === AREA 3: Combat Hall ===
    // Large hall with pillars
    |> Interior.doorway West 2 3
    |> Layout3D.section 20 0 0 (Interior.room 16 5 16 FloorCell WallCell CeilingCell)
    
    // Pillars for cover
    |> Layout3D.section 4 0 4 (Interior.pillar 4 PillarBase PillarMid PillarTop)
    |> Layout3D.section 12 0 4 (Interior.pillar 4 PillarBase PillarMid PillarTop)
    |> Layout3D.section 4 0 12 (Interior.pillar 4 PillarBase PillarMid PillarTop)
    |> Layout3D.section 12 0 12 (Interior.pillar 4 PillarBase PillarMid PillarTop)
    
    // Enemy spawns
    |> Layout3D.section 6 2 4 (Layout3D.set 0 0 0 EnemyCell)
    |> Layout3D.section 14 2 10 (Layout3D.set 0 0 0 EnemyCell)
    
    // Exits to other areas
    |> Interior.doorway East 2 4
    |> Interior.doorway South 3 4
    
    // === AREA 4: Upper Balcony ===
    // Stairs up
    |> Layout3D.section 20 0 2 (Interior.stairs 2 5 5 StairCell)
    
    // Balcony (open-top for exterior feel)
    |> Layout3D.section 20 5 0 (Interior.openRoom 12 3 16 FloorCell WallCell)
    
    // Windows looking down into hall
    |> Interior.window North 4 2 1
    |> Interior.window South 4 2 1
    
    // Treasure
    |> Layout3D.section 28 6 8 (Layout3D.set 0 0 0 ChestCell)
    
    // === AREA 5: Exit ===
    // Shaft to next level
    |> Layout3D.section 0 0 0 (Interior.shaft 2 2 10 WallCell)
    |> Interior.doorway South 2 3

let level =
    CellGrid3D.create 40 10 20 (Vector3(2f, 2f, 2f)) Vector3.Zero
        |> Layout3D.run levelSection

Common Interior Patterns

The "Tunnel Run"

Narrow corridor with no rooms, long linear passage:

let tunnelRun =
    section
    |> Interior.corridorX 20 2 3 FloorCell WallCell CeilingCell

Use for: - Introductions - Tension-building sections - Connecting distant areas

The "Hub and Spokes"

Central room with 4 radiating corridors:

let hubAndSpokes =
    section
    // Central hub
    |> Interior.room 10 4 10 FloorCell WallCell CeilingCell
    |> Interior.doorway North 2 3
    |> Interior.doorway South 2 3
    |> Interior.doorway East 2 3
    |> Interior.doorway West 2 3
    
    // North spoke (treasure)
    |> Layout3D.section 4 0 4 (Interior.corridorZ 6 2 3 FloorCell WallCell CeilingCell)
    |> Layout3D.section 4 0 0 (Interior.room 6 4 6 FloorCell WallCell CeilingCell)
    
    // South spoke (enemies)
    |> Layout3D.section 4 0 10 (Interior.corridorZ 6 2 3 FloorCell WallCell CeilingCell)
    |> Layout3D.section 4 0 10 (Interior.room 6 4 6 FloorCell WallCell CeilingCell)

The "Multi-Floor Building"

Three floors connected by stairs and shaft:

let multiFloor =
    section
    // Floor 1: Lobby
    |> Layout3D.section 0 0 0 (Interior.room 10 4 10 FloorCell WallCell CeilingCell)
    
    // Stairs to floor 2
    |> Layout3D.section 10 0 3 (Interior.stairs 2 5 5 StairCell)
    
    // Floor 2: Offices
    |> Interior.doorway West 2 3
    |> Layout3D.section 0 5 0 (Interior.room 10 4 10 FloorCell WallCell CeilingCell)
    
    // Shaft to floor 3
    |> Layout3D.section 8 0 8 (Interior.shaft 2 2 5 WallCell)
    
    // Floor 3: Rooftop
    |> Layout3D.section 0 10 0 (Interior.openRoom 10 2 10 FloorCell WallCell)

Design Tips

Spatial Awareness

• Room size matters: Large rooms feel grand but reduce tension. Small rooms feel claustrophobic but increase intensity.
• Corridor width: 2 cells for tight passages, 3-4 for comfortable movement.
• Ceiling height: 3-4 cells is standard for human-scale. 2 cells feels cramped, 5+ feels cavernous.

Flow and Navigation

• Doors should be obvious: Place doors on wall centers, mark with different tiles.
• Avoid dead ends: Every area should lead somewhere (unless it's a deliberate trap).
• Provide shortcuts: Players appreciate backtracking prevention (stairs between floors, hidden passages).

Visual Clarity

• Distinguish surfaces: Different tiles for floors, walls, ceilings helps orientation.
• Mark exits: Doors, stairs, and shafts should be visually distinct.
• Light sources: Torches, lamps, or windows break up monotony.

Playtesting

• Enemy placement test: Can enemies reach players? Are there safe spots?
• Line of sight: Check that corners provide actual cover.
• Door usability: Do doors block movement awkwardly? Are they wide enough?

See also: API Reference for complete Interior module documentation