The Preview Column

7 min readUpdated Aug 2026

Select one design in the file manager and the right-hand column fills with a 3D view you can drag to turn, that design's public parameters, and the download buttons: three for a model, two for a smart object, which has no .kpy to give you. It is the fastest way to hand somebody an STL: pick the file, set the numbers, download, without ever opening the editor.

With nothing selected the right column reports how much of your allowance is gone, or picks up where the tutorial left off.

The picture is from the last save, not from now

Selecting a design regenerates nothing. What appears in the stage is the 3D preview that was baked the last time the document was saved. It is not a render of the file as it stands, and it is not a photograph: it is a live 3D view of a stored copy, which is why you can spin it.

Change any parameter and the geometry is rebuilt for real, a quarter of a second after you stop moving the slider. A status line appears under the parameters while that happens, reading Starting geometry engine… and then Rebuilding preview…. From that point on you are looking at current geometry.

Until you touch a parameter, you are not. There is no badge, no timestamp and no visual difference between a freshly rebuilt view and a stored one. If you edited the design in another tab, or a thumbnail bake failed, the stored picture can be arbitrarily out of date and nothing says so.

Parameters

Only parameters marked exported appear here, in the order they have in the editor's parameters panel. Text parameters are left out. If the list is empty you get This design exposes no public parameters., which means the author did not publish any, not that the design has none.

Each type gets the control it deserves. A number with both a minimum and a maximum becomes a slider with its value and unit beside it; a number without a range becomes a plain input; a yes-or-no becomes a switch; a list becomes a dropdown.

Values start at whatever the document was saved with. Only the ones you actually change are treated as overrides, so every parameter you leave alone keeps its expression and its relationship to the others. That is what stops a slider you never touched from breaking a formula somewhere else.

Those overrides feed straight into the downloads. What you set here is what comes out of the STL.

The calibration box

If the design refers to any calibration constants, a Calibration used box lists them with the value your active print setup currently gives each one, and the note Values from your active print setup are baked into downloads.

That is not decoration. The setup selector at the top right of the file manager is the one live control in that header, and switching it changes the numbers that go into the file you download. Check this box before downloading a part with printed fits in it. Real printed clearances explains what those constants are for.

Downloading

Under Download sit STL, STEP and, for a model, .kpy. A smart object gets the first two only.

What each button gives you

Button	What it is	Plan
STL	The triangle mesh, ready for a slicer, built with your current parameter values	Free, always
STEP	Exact B-Rep geometry for another CAD package	Maker
.kpy	The whole parametric document: features, sketches, parameters. Models only, never smart objects	Maker

On the Free plan a small padlock is the only hint that STEP and .kpy are locked: they still look like buttons, and clicking one opens the upgrade panel instead of a download. Exporting Your Model covers what each plan gets.

A download that fails reports Download failed — try again. and nothing more specific, because the underlying reason is discarded. If a retry does not clear it, open the design in the editor and export from there, where the error survives.

The rest of the card

Above the stage sits the name and the kind. Below it, Open and a square button that opens the design in a new tab. Then the metadata block: Location, Created, Modified and Last opened.

Two absences to save you hunting. The dates carry day, month and time but no year, so a file from last spring and one from this morning read alike at a glance. And nothing here reports file size, body count or parameter count.

Some selections give you something else instead of the download block:

A design in the trash shows Deleted and the date, with no Open button. Restore it first.
A code smart object shows Code Smart Object — open it in the editor to preview. There is no preview to build without running the code.
A design that has never been saved with geometry shows This design has no saved geometry yet.
A smart object you saved from the store shows its category, its version, the author's handle and one action, Remove from saved. You cannot download or open somebody else's store listing from here.

When nothing is selected

Click empty space and the column becomes Your space: a ring, your plan, and counts of models, smart objects, folders and items in the trash.

The ring measures models against the Free plan's ten, not storage. It turns amber as you approach the limit and red at it. On the Maker plan it is a full ring with an infinity sign, because there is no model limit to draw.

If you have not finished the guided tutorial, the whole column is the tutorial panel instead, with your progress and a button to carry on. It has no dismiss, and it goes away when the tutorial is done.

When it fails

The one message that belongs to this column alone is:

Preview failed — showing the saved thumbnail.

The rebuild you asked for did not complete, and the stage has fallen back to the stored picture. Two things cause it in practice: a parameter combination that the model cannot actually build, and a document too heavy to rebuild here. Open the design in the editor, set the same values, and read the real error on the timeline. See When a Step Goes Red.

That message is about the picture alone. The download you take next still builds itself from the document, so it will either be the real geometry at your values or it will fail for the same reason the preview did. What it will never be is the thumbnail you are looking at.