Building a lighting or performance gym

A gym is a level that exists to be measured — every prop laid out, evenly spaced, under controlled lighting, so you can change one thing and see what it does to all of them at once.

They’re tedious to build by hand, which is why most teams don’t have one. This builds you one from a folder.

1. Turn off transient

By default nothing Mosaic spawns is saved into your map. That’s the right behaviour for a quick look, and the wrong behaviour here, because a gym needs to persist.

Open a new empty level. Right-click, Mosaic - Asset Audit ▸ Asset Zoo, and in the core settings untick Transient actors.

Set your Root folders, press Generate, and save the level when it finishes. You now have a real level full of real actors that you can light, profile and hand to someone else.

2. Light it

Everything is laid out flat and evenly spaced, which is what makes a gym useful:

• one directional light and one sky light gives you a baseline everything is judged against
• rotate the sun and watch the whole set at once, instead of one asset at a time
• swap the sky and you’re comparing your entire prop library under two lighting conditions in a couple of minutes

Because assets sit at true physical size, the shadows are honest. A gym built by hand at arbitrary scale isn’t telling you much.

3. Profile it

The same level is a reasonable profiling target. Everything is on screen at once from a top-down camera, so stat unit, stat rhi and the shader complexity view all have something to chew on.

It won’t match in-game conditions — nothing is occluded and there’s no gameplay running — but it’s a consistent thing to measure against week after week, and the consistency is the value.

4. Keep it current

Re-running Asset Zoo on the same folder replaces the previous picture, so refreshing the gym after a delivery is one right-click. Save the level again afterwards.

If you want several gyms in one level — props, vehicles, foliage — run it once per folder. Each picture lands beside the last rather than on top of it.

Worth knowing

Turning transient off is the one setting that lets a picture end up in a saved map. Turn it back on afterwards if you go back to using Orphan Zoo, because a saved gym counts as real usage, and an audit would then report those assets as being in use.