The dimetric camera

The projection is a setting

Game “isometric” is 2:1 dimetric: the diamond of one ground cell is twice as wide as it is tall, 256×128 px here, and its edges run at 26.565°. True 30° isometry is not what the kit uses and the ANDON refuses it.

That angle is a camera setting, not an art direction note. Every plate in assets/dimetric/ was rendered by assets/dimetric/camera/dimetric_60_45.py under headless Blender:

Knob	Value
Camera	orthographic, rotation X 60°, Y 0°, Z 45°, Sensor Fit horizontal
ortho_scale	(N + M) / √2 for an N×M footprint (1.41421 per tile when square)
Resolution	128·(N+M) wide × 128·K tall; the foot vertex sits on the bottom row
Alpha	Film Transparent, from the Combined pass. Never keyed, never matted
Light	one Sun, one azimuth, the same for every plate (sun_euler_deg in MANIFEST.json)
Scale	one Blender unit = one tile; a person is 128 px; a one-storey facade is 384 px (1 : 3)

World +X projects to screen down-right, world +Y to screen up-right. A footprint’s near vertex is world (N, 0, 0), which is what TileMapLayer DIAMOND_DOWN expects.

The Godot side

stage/iso/ is the kit:

• iso_math.gd — the only place Cartesian ↔ 2:1 conversion lives, so a TileMapLayer and an actor cannot disagree about where a cell is. Tested round-trip.
• iso_world.gd — one TileMapLayer (TILE_SHAPE_ISOMETRIC, TILE_LAYOUT_DIAMOND_DOWN, 256×128), Y-sorted, ground atlas built at load from the manifest’s tiles (converted to RGBA8 before any blit), the structures and actors as siblings under one Y-sorted parent, click-to-cell, the follow camera.
• iso_structure.gd — a building plate cut into 128 px vertical strips, each a 1×1 drawable owned by the front-edge cell beneath it, art hung upward with a texture origin. One drawable per diamond is the only order a painter’s sort can honour; multi-cell tiles sort wrongly under Y-sort in Godot (#92682).
• iso_actor.gd — a Foundry HD sprite bound through CanvasTexture (albedo + normal), foot pivot, with a contact blob drawn show_behind_parent at the actor’s own z_index. Not z_index -1: nodes only Y-sort against each other on the same z_index, so a negative index draws under the floor.
• iso_prop.gd — one-cell props with a foot origin.

Two Godot facts the code works around: local_to_map() is rectangle-bounded on isometric tiles, so click-to-cell runs a diamond test after it; and moving the active Camera2D does not refresh the canvas transform in the same frame, so force_update_scroll() is called before any pick during a walk.

The standing cells are not computed here: iso_world.gd takes each townsperson’s cell, zone and facing — and the anchor of every zone’s 3×3 — from the presentation block World Forge authors onto fixtures/pack.json, falling back to fixtures/harbour-occupancy.json and then to a derived corner cell when the pack carries none.

Lighting

One 2D canvas. Torches are PointLight2Ds with a nonzero height (the light’s Z in pixels), which is what makes a Foundry normal map read at all. The cap is 16 lights per canvas item, compiled into the renderer, and a two-light torch rig costs two of them; the harbour budgets accordingly. Directional 2D shadows are infinitely long and height never shortens them, which is why the blob is the only height cue.

The ANDON

assets/dimetric/andon/iso_andon.py runs on every PNG before it may enter res://. Exit 0 only when every gate passes; the log JSON sits beside the file and MANIFEST.json is regenerated from those logs.

Gate	Checks
0	decoded format is RGBA (an RGB plate is what emptied the ground atlas once)
1	opaque ratio: ground 0.35–0.62 · structure < 0.85 · prop < 0.70
2	all four 8×8 corner blocks are alpha 0
3	lowest-row slab edges fit 26.565° ± 1.5°
4	slab width = 128·(N+M) ± 4 px
5	used-rect centre X = image centre ± 2 px (the foot origin)
6	dimensions: 256×128 ground · 128(N+M)×128K structure · 256×128 or 256×256 prop
7	no checkerboard baked into RGB (per-tile correlation on high-passed luminance)
8	some intermediate alpha exists (a painterly edge, not a thresholded one)
9	no loader resize: the file is the size Godot draws

Plates that fail are kept as evidence under assets/dimetric/_rejected/ (a .gdignore folder), never salvaged. The eight original white plates under assets/iso/ live there now.

The library

assets/dimetric/
  MANIFEST.json        generated: every plate, its kind, footprint, path, ANDON result
  camera/              dimetric_60_45.py, diamond_clip.py, calibration_square.png
  andon/               iso_andon.py, build_manifest.py
  ground/              dirt_a, dirt_b, stone_a (256×128 diamonds; colour bled past the edge, then clipped)
  structures/<id>/     beauty.png + sidecar.json (slab row, strip width, storeys, azimuth)
  props/<id>/          beauty.png + sidecar.json (foot pixel; light_px for the torch)

The runtime reads MANIFEST.json and loads only entries whose andon is pass. A plate is not a room. Rooms, gates, and where a person stands are authoring levers in World Forge. The stage never generates art, and the camera script never touches the stage.

The lie budget

Hashed by the engine: zone id, facing at rest, who is in which zone at tick T.

Allowed lies: the destination highlight on the input frame; the walk tween after an admitted zone change; camera trauma and HUD flash from felt.uiEffects; walking inside a zone, which the sim never hears.

Forbidden: analog velocity as truth; hashing a tween’s t; interpolating occupancy; a physics body that collides on its own; juice that writes hashed state. There is no CharacterBody2D in this client and there will not be one.