Isometric scene engine for B4L projects: site plans, plants and buildings drawn as SimCity-style views that you can pan, zoom, rotate, cut open by storey and click for details. One Rust binary does everything:

Studio: a GUI editor in the browser for people who don't code. You add objects from a palette, drag them into place, and edit their properties in forms.
MCP server: AI agents (Hermes and others) edit the same scene with the same operations; their changes show up live in an open Studio.
Build: a self-contained HTML page with every view prerendered, or standalone SVGs for documents.
Engine and scripting: everything you can place is a prefab written in Rhai. Projects add their own prefabs, scripts and colours without touching the engine.

The engine is a Rust port of the hand-written JS views in cnx_vinyl (fleet calculator), cnx_scuba (centre view) and mooban (estate view), and it keeps their look: same projection, depth sort, face shading, palette and viewer behaviour.

Quick start

cargo build --release            # target/release/isokit.exe (one file, ~7 MB)

isokit new C:/dev/myproject/site-view     # starter project
isokit studio C:/dev/myproject/site-view  # opens the editor in the browser
isokit build C:/dev/myproject/site-view   # dist/index.html, no server needed

Try the demo: isokit studio examples/demo.

Studio (for everyone)

Do	How
Add	pick an object on the left, click on the map (Shift-click places several)
Select	click it on the map or in the object list
Move	drag it, or arrow keys by the snap step (0.1 / 0.5 / 1 / 5 m)
Turn	R / Shift+R or ⟲ ⟳
Edit	the right panel: size, storeys, colours, solar, tooltip text, label, levels
Copy / delete	Ctrl+D / Delete; Ctrl+Z / Ctrl+Y undo and redo
Look	drag the ground to pan, Ctrl+wheel or pinch to zoom, ↺ ↻ rotate, Site / GF / 1F levels

Every change is saved to scene.json at once. When the file changes on disk (an agent, git pull, another editor), the Studio reloads it, and that change can be undone like any other.

Agents (MCP)

While the Studio runs, it also serves MCP over HTTP at http://127.0.0.1:7878/mcp. Without the Studio, run isokit mcp <project> over stdio. In Hermes (config.yaml):

mcp_servers:
  isokit:
    command: C:\dev\isokit\target\release\isokit.exe
    args: [mcp, C:\dev\myproject\site-view]

Tools: project_info, list_prefabs, list_objects, get_object, add_object, update_object, remove_object, duplicate_object, apply_ops (batch, one undo step), set_params, render_view, check_project, build_html, undo, redo. Bad input comes back with a message that says what is allowed, e.g. the list of types or a prop's range.

A project

isokit.toml   title, levels, parameters, theme files, prefab libraries
scene.json    the objects (edited by the Studio and agents)
scene.rhai    optional script, drawn before the objects
lib/*.rhai    optional project prefabs (listed under prelude)
theme.toml    optional colours and materials

An object in scene.json:

{ "id": "hall", "type": "building", "name": "Workshop", "x": -12, "y": 6, "rot": 90,
  "props": { "w": 24, "d": 12, "floors": 2, "pv": true },
  "tag": "Workshop", "info": "Two storeys, solar on the roof", "levels": [] }

Coordinates are metres: x points east, y north, z up. x, y is the centre of the footprint, and rot turns the object in 90° steps. Levels: site (or any other id) shows buildings closed, while gf, 1f, 2f … cut them open at that storey.

Commands

Command
`isokit new <dir>`	starter project
`isokit studio [dir] [--port N] [--no-open]`	GUI editor + `/mcp` + `/view` live preview
`isokit mcp [dir]`	MCP over stdio
`isokit build [dir] [-o file]`	self-contained HTML (all levels × 4 rotations)
`isokit render [dir] -o x.svg [--level gf] [--rot 2] [--light]`	one view as SVG
`isokit check [dir]`	lint: unknown types, props out of range, script warnings, NaN, node budget, unstyled classes
`isokit prefabs [dir]`	object types and their properties

Architecture

crates/isokit-core     projection (4 rotations), primitives, sprites, depth sort, SVG   (no deps but serde)
crates/isokit-theme    TOML palettes / materials / rules -> CSS; built-in default theme
crates/isokit-script   Rhai runtime: drawing API, prefab library (stdlib/*.rhai), scene document driver
crates/isokit-project  project folder, document ops, export, check, Workspace (undo, reload), MCP tools
crates/isokit-cli      the `isokit` binary: Studio HTTP server, MCP stdio, build/render/check
viewer/                isokit-view.js/.css: pan, zoom, levels, rotation, tooltips (any page can embed it)
studio/                the Studio GUI (served by `isokit studio`)
examples/demo          demo project

The layers are independent. A Rust program can draw with isokit-core alone. isokit-script reads sources from memory, with no disk access, so the same runtime can later run in the browser as WASM. The Studio and MCP both apply the same ops::Op JSON operations through a Workspace.

Writing prefabs and scripts: docs/SCRIPTING.md. Plans: docs/ROADMAP.md.

Development

cargo test                                   # engine, runtime, ops, demo, MCP
cargo clippy --all-targets -- -D warnings
isokit studio examples/demo --port 7890 --no-open &
uv run --with playwright python tools/check_studio.py <shot-dir> http://127.0.0.1:7890   # GUI + MCP end to end (Edge)

Set ISOKIT_ASSETS=C:/dev/isokit to serve viewer/ and studio/ from disk, so you can edit the GUI without rebuilding. tools/css2theme.py converted the original views' CSS into crates/isokit-theme/themes/default.toml.

README.md Unescape Escape

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