Blockout first, art last: how to texture a playtested gray level with AI

Build the level in gray, playtest it, then add art: that is the order Epic Games recommends in its Unreal Editor for Fortnite documentation, and AI tools released in late October can now handle the art step. Epic describes greyboxing, or blockout, as "making a playable rough draft of a level" and says to add props and art once the level plays well.

A graybox is made of untextured shapes such as blocks, ramps and cylinders. Epic's page lists scale and layout as what to test at this stage. In our view it also suits coding agents, because placing primitives is a layout job, not an art job; the AnyGameRenderer paper's authors similarly write that agent-built games usually end up as gray blockouts and colored primitives.

The clearest worked example is trompe, the Apache-2.0 tool from Patch (patch-gg) that we covered in "Open-source tool trompe paints a gray game blockout into a textured level" (with its demo's cost). Its README sets out the steps:

• Export the blockout as a .glb file with UVs and the Y axis up.
• Describe the look as materials ("weathered limestone"), not objects; the README warns that named objects get painted onto walls.
• trompe places cameras where a player could stand, plus roof, aerial and hole-filling views.
• An image model on fal paints each view under overcast light, so the result works as albedo (plain surface color).
• The paintings are projected back onto the geometry and baked into one texture, exported as glTF.

Nearby tools cover other steps. AnyGameRenderer, a research paper reported by Glonce, repaints gray gameplay footage into polished video while keeping entities in place, though Glonce notes no code or weights are out (see "AnyGameRenderer model repaints gray-box gameplay footage into polished visuals"). Hi3D v1.0, released October 23 on Hugging Face, refines a coarse mesh guided by a reference image, and Patch's anymove, released October 27, extracts creature animation from one AI video.

Why it matters

If art is a replaceable last layer, the playable gray level stays the source of truth. A developer or agent can rework the layout cheaply, texture it once it plays well, and in principle repaint it in another style later.

Limits and caveats

We haven't tested trompe, and its figures are the project's own. The README lists limits: levels need UVs, walls facing narrow gaps can stay gray, overhangs can catch misprojected patches, and parallel painting leaves seams. As we read it, the texture is tied to the mesh's UVs, so a reworked layout would likely need a fresh run; --resume only fills areas a saved run missed. Cost grows with view count: the README prices mostly blank views on FLUX 3 Klein at $0.009 and fills on Fibo 2 Edit at $0.04.

How to try it

• Start with a small blockout whose layout you have already playtested.
• Check its UVs, and name parts through glTF materials, since trompe builds its prompts from those names.
• Run with a low view count, or use the prompt-test script with --dry to check prompts without calling a model.
• Keep the gray version in source control so you can repaint after layout changes.

Next on trompe's list, according to its README: a ComfyUI provider for local models and an automatic retouch pass for seams and stray patches.