Performance & Budgets
How big a scene can get, how to see where it stands, and what the app does on its own when a scene is more than your machine can draw.
Everything on this page is local. A budget is a fact about your graphics card and your tab: nothing here is saved with the scene, replicated to a peer or undoable, and two people on different hardware are allowed to disagree about all of it.
The meter
The object count in the status line carries a coloured dot:
| Dot | Meaning |
|---|---|
| 🟢 Green | Within budget. Nothing to do. |
| 🟡 Amber | Over the comfortable ceiling on at least one measure. Still fine, but worth knowing. |
| 🔴 Red | Over the second ceiling. This is what the gateway and the auto-stops below read. |
Hover it and it names what is over (Scene budget: over on draw calls / frame, triangles / frame). Click it and the Statistics window opens — the same window as the burger menu ▸ Statistics.
What the Statistics window counts
Seven budgets, each with its own dot, its value, and its two ceilings beside it:
| Budget | Why it is a budget |
|---|---|
| Objects | Every object is at least one draw call, one wire message per joiner, one row in the object tree and one node in every traversal. |
| Triangles / frame | Vertex and fill cost, counted across every render call in a display frame — the shadow pass draws each mesh a second time, so the number is about twice a naive count. |
| Draw calls / frame | CPU time per call. In a many-object scene this, not triangle count, is what binds. |
| Textures | A stand-in for graphics-card bytes. The tab is killed on mobile, and the 3D context is lost on desktop, when it runs out. |
| Geometries | Buffers held on the card. A leak shows here first — a delete that never gave its memory back. |
| Frame time p95 | An FPS average smooths a stutter away; p95 is the frame you actually feel. |
| Long tasks / min | The direct measure of "the window froze" — a task over 50 ms blocks input. |
Hovering a row's name says why that budget exists.
Below the table: frame times as p50 / p95 / p99, long tasks in the last minute with the worst one, the JS heap where the browser reports it, meshes and how many are hidden, how many objects are still arriving, and a Wire table of per-message-type counts in and out over the last few seconds. The refresh button re-reads everything and resets the wire counters.
Two profiles
The same scene is comfortable on a desktop and fatal on a headset, so the ceilings come in two sets. The line at the top of the window says which you are being judged against — desktop or VR / mobile.
The whole set rides along in the diagnostics bundle.
The overload gateway
Four stages, in the order a heavy scene meets them. Nothing here is silent, and every stop is reversible.
1. A big scene arriving does not freeze you
Objects are created in slices rather than all at once, the viewport is refreshed once a frame instead of once per object, and an object list of thousands of rows draws only the rows you can actually see. A scene that used to take minutes to land while the tab sat frozen now arrives while you watch it.
2. Something oversized asks before it lands
Opening a file big enough to hurt is held at the door:
This scene is large — "Arena" has 4,812 objects — above the 3,000 recommended for this device. It may be slow, and on a phone or headset the tab can be closed by the browser.
with Open anyway and Cancel. An imported model gets the same ask with a third way out; see Importing files.
This asks only where a person opened something. Travelling to a scene, a peer's proposal and an autosave restore never stop at a dialog nobody is standing at.
3. A simulation that cannot keep up stops
When a physics step takes longer than a frame lasts — over 24 ms, for half a second of steps in a row — the simulation stops once and says so:
Physics stopped — the simulation was too slow for this device (over 24ms a step). The scene is intact.
with Resume. Consecutive, not cumulative: one hitch while a texture uploads is not a scene that is too heavy.
4. A window that cannot draw pauses instead of freezing
When frames each take longer than a quarter of a second, for ten frames in a row, drawing stops and a panel explains it rather than leaving you looking at a tab that appears to have crashed. Nothing is lost, and autosave keeps running while the panel is open. It offers:
- Save now — the scene is intact, because it lives in the page rather than on the graphics card.
- Reduce — stop drawing the newest objects on this device until the scene fits the budget. Peers are unaffected and nothing is deleted; Show them again puts them back.
- Resume — carry on. The next few frames are expected to be slow, so a grace window stops it from immediately re-pausing.
A lost graphics context is a different panel
If the browser takes the 3D context away — a driver update, a graphics reset, a phone under memory pressure — you get its own panel instead, with a button to save the scene. The view restores itself when the browser hands the context back.
The quality governor
Before any of the stops above, the app tries to keep the frames. Settings â–¸ Scene â–¸ Reduce quality when the scene is heavy (on by default): when a heavy scene cannot hold 30 frames a second on this machine, quality comes down one step at a time, and each step is given back as soon as frames recover.
Shadows go first, then resolution, then effects — measured rather than guessed, because the shadow pass draws every mesh a second time and so is where the cost actually is:
- Shadows off
- Resolution 85%
- Resolution 72%
- Ambient occlusion off
- Resolution 61%
- Scene look (post-processing) off
- Resolution 50%
- Fewer particles
- Your camera updates to peers halved
While it is acting, a Reduced quality (scene is heavy) chip sits beside the object count, and its tooltip names exactly which steps are in force. Click the chip to hold it there — useful when you would rather have steady frames than watch quality breathe in and out — and click it again to give full quality back. The first time it ever acts in a session it also says so in a toast, because the chip lives in the object list's footer and that window can be closed.
Nothing the governor does changes the scene for anybody else, and nothing it does is written to a preference: it is a fact about this device right now.