Playground guide

The Playground is a 3D editor with a built-in AI: the Holodeck computer. Open https://arx.dev/playground, start a program, and tell it what to build.

No account needed: as a guest your programs live in your browser, with a few AI requests a day (and no AI textures). Sign in — free — to keep them on every device and build more; the programs you made as a guest come with you.

Talking to the computer

Type in the command bar at the bottom and press Engage, or use your voice:

• Mic button (or hold V): speak one command; it’s transcribed and run. A leading “Computer,” is fine — it’s stripped.
• Voice mode (the Voice button): hands-free. The computer listens whenever it’s idle, runs what you say, and answers out loud.

Good requests name a setting and the things in it, then refine:

• “Build me a forest with a small cabin and a campfire, at night.”
• “Make the trees autumn orange.” “Add a pond near the cabin.”
• “Give me a camera overlooking the village and one at street level.”
• “Cobblestone ground.” (paints a new texture) · “Remove the rocks.”

While it works you see each step — searches, placements, materials — and the scene fills in live. Halt stops it. Each request builds on what’s there.

Editing by hand

It’s a real editor, Unity-style:

Every edit is saved immediately and shows up in every other open editor (browser or Unity) for that scene.

Organising the scene

The Hierarchy is a tree of folders — Nature/Trees, Nature/Rocks, Village/Houses. The computer files what it builds; you can too:

• Folder field in the Inspector (type Nature/Bushes — new folders appear as needed), or drag an object onto a folder in the tree (onto empty space to take it out).
• Click a folder to open it in the Inspector: rename or move it (Nature → Wilds/Nature), mark everything static, hide, lock, move everything by an offset, focus, or delete the lot.
• The ● and 🔓 buttons on a folder row hide it and lock it.

Static objects are scenery — foliage, rocks, fences. They’re drawn with GPU instancing (thousands stay fast) and can’t be clicked in the view, so you don’t grab a bush when you meant the cabin; pick them in the Hierarchy. Scattered scenery is static by default. Locked folders can’t be selected in the view or moved.

Terrain

The Terrain tab turns the flat floor into endless procedural ground: hills, mountains, plains, islands, dunes. It’s seeded — the same settings give the same landscape for everyone, forever in every direction.

• Relief (metres of height), Features (size of hills, metres), Rugged, Seed (🎲 for a new landscape), Flat centre (a level building site around the origin) and Water (sea / lake level).
• Sculpt — Raise, Lower, Flatten (to where the stroke started), Smooth, Noise (roughen), Terrace (stepped slopes, with a step height), and Path: drag along a line and let go to carve a road (flattened, following the ground, painted), a river (dug below the ground — dig under the water level and it fills) or a ridge. Every brush has a radius, strength and hardness (soft edge … flat top).
• Paint — ground layers (grass, dirt, sand, rock, snow, path, moss; auto erases paint); the Scenery brush (find assets, pick a few, set a density, and drag to paint static, grounded trees, bushes or rocks — it keeps off water and cliffs); and the Eraser (scenery only, or everything unlocked).
• Ground layers — recolour any layer, or give it a material: generate a texture in the Inspector (“worn cobblestones”) and pick it for path, and every road is cobbled.
• Paint by rule — snow above a height, rock on slopes steeper than a value, sand just above the water — within a radius of the view centre.
• Undo terrain edit (or Ctrl+Z with the Terrain tab open) steps back through sculpt, paint and path edits; Reset sculpting drops them all. Pick a tool and drag on the ground; right-drag still looks around; Esc puts it down.

Objects stand on the terrain and follow it when it changes. Dragging one across the ground keeps it on the surface; lifting it (a new height) unpins it. Ground colours come automatically from slope, height and water — rock on cliffs, sand at the shore, snow on high mountains — unless painted.

Ask the computer too: “rolling hills with a lake”, “flatten a spot for a castle”, “a cobbled road from the cabin to the shore”, “a river through the valley”, “snow on the peaks”.

Cameras and moving around

• Edit — the editor camera, Unity-style: right-drag to look around, and hold the right button with WASD / Q E to fly (Shift faster); middle-drag pans, the wheel zooms, Alt + left-drag orbits, the arrow keys move any time, F frames the selection. Switching between Edit, Walk and Fly keeps the camera where it is.
• Walk — first person: click the view to look around, WASD to move, Shift to run, Space to jump. You stand on things and bump into walls. Click a door (or press F looking at it) to open or close it.
• Fly — free flight: WASD, Space / Q up and down, Shift fast.
• Scene cameras — placed by you (Cameras ▾ → Add camera from this view) or by the computer. Keys 1–9 jump to them; Esc returns to the editor.

VR

With a WebXR headset (Meta Quest, Pico, Apple Vision Pro, a PC headset in Chrome / Edge), open the Playground in the headset’s browser and press VR in the top bar. You start where the editor camera was looking.

The panel on your left wrist shows what the computer is working on and what it said. Static scenery and locked folders can’t be grabbed — unlock or un-static them in the editor first.

Buildings, doors and placement

• Structures — ask for any walled building (“a sci-fi habitat with two doors”, “a two-storey barracks”) and the computer builds it from the pack’s modular floor, wall, door and window pieces on an exact grid: walls meet without gaps or overlaps, the ground underneath is levelled, storeys stack and a roof closes it.
• Doors — doors, gates, hatches and lids can be interactive: they swing on a hinge, slide sideways or lift like a garage door. The computer makes building doors interactive, or select an object and choose a behaviour under Interaction in the Inspector (hinge side, swing angle, which part of the prefab moves, and whether it opens by itself when you walk up to it). Click it in Walk / Fly, use the trigger in VR, or Open / Close in the Inspector — the state is saved.
• Placement — an object’s position is the centre of its footprint at its base, whatever pivot the artist gave the model (Synty walls pivot on an edge, ships in the middle), so things sit on the ground and line up. When the computer places something inside something else it’s told and moves it, it checks the whole layout before finishing, and — while you have the editor open — it takes a picture of the scene to look at its own work and fix what looks wrong.

Usage

The Usage tab shows what each request cost: tool steps (and which tools), model calls, tokens, seconds and LLM cost in USD, plus totals for the program (including generated textures).

Materials and textures

Select an object and use Material in the Inspector, or the Materials list (nothing selected):

• New material — colour, roughness, metalness, glow, opacity, and a pattern (checker, bricks, tiles, wood, marble, …) with a tile size in metres.
• Generate texture — describe a surface (“mossy cobblestone”) and an AI paints a seamless texture (~6 seconds).
• Tint assets — keeps a library model’s own texture and recolours it (best for trees, rocks and props); replace texture suits primitives and the ground.

Keeping a consistent style

Packs use different colour palettes. The Assets ▾ menu locks a program to one vendor (e.g. Synty) or a single pack; the computer and the Library tab then only use assets from it. New programs start locked to Synty. The computer also prefers prefabs — the vendor’s finished objects — over bare models.