Greyboxing is building a level from plain shapes at true scale, to test movement, sightlines and pacing before any art exists.
Why it comes first
- Scale is the hardest thing to fix later. A corridor that feels wrong at final art is a corridor that has to be rebuilt, along with everything attached to it.
- Movement is felt, not designed. Jump distances, cover spacing and door widths only reveal themselves when walked.
- Sightlines drive everything. What the player can see from where determines encounter design, and it is entirely a geometry question.
Working at true scale from the start
Set a character-height reference and never build without it visible. Most greybox mistakes are scale mistakes, and they compound: a slightly-too-large room becomes a slightly-too-long traversal becomes a pacing problem three rooms later.
Where generated assets fit
They do not replace the greybox — they come after it. The sequence that works is: greybox in plain shapes, test it, then populate. Populating first produces a level designed around whatever assets happened to exist, which is how you get a game that feels like a collection of props.
When to leave the greybox
When the layout stops changing. If you are still moving walls, art on those walls is work you will redo. The transition point is a design decision, not a schedule one, and pushing it earlier to look productive is the most reliably expensive mistake in level production.