Editing a Part You Have Built

To change something you built an hour ago, click its pill in the timeline. Its panel opens where the toolbar was, the viewport rolls back to show the part as it was at that moment, you change the value, and you press OK. Everything downstream rebuilds on the new answer. That loop is the whole reason to model parametrically.

The loop, once through

Take a bracket: a rectangle sketched on the front plane, extruded 6 mm, two holes cut through it, and a fillet on the outside corners. The holes came out at 5 mm and the bolts need 5.4 mm.

1. Click the cut's pill in the timeline. The floating toolbar disappears and the cut's settings panel takes its place, at the top-left of the viewport. The panel header shows the step's coloured icon and its name.
2. The viewport rolls back. The fillet is gone from the screen, and so is anything else built after the cut. You are looking at the part as it stood when this step ran.
3. Change the diameter to 5.4. The change is applied as you type, so the holes in front of you widen while the panel is still open.
4. Press OK, or Enter, which does the same thing. The panel closes, the toolbar comes back, and the fillet reappears, rebuilt around the new holes.

Nothing about that loop is special to a cut. Every step in the timeline opens the same way, shows you the same rolled-back view, and commits the same way.

What the viewport is showing you

Opening a step rolls the 3D view back to that step and hides everything after it. This is a display change only. The playhead does not move, no step is disabled, and closing the panel restores the full model.

Four kinds go one step further back than that and hang a live ghost in the gap: an extrude, a push face, and the two kinds of smart object, placed and code. You see the model without the step you are editing, plus a translucent preview of what your typing is currently producing. That is deliberate: it is the only way to judge a depth against the face it starts from.

Two settings switch the ghost back off. An extrude with a stepped profile, and an extrude or push face set to stop at a face you picked, both show the committed result instead, because neither has a preview to draw. Every other step in the timeline is the plain case: no ghost, no extra roll-back, and the real body regenerating under your hands as you type.

If a step you are editing seems to have made half the part vanish, this is why. Close the panel and the rest comes back.

What actually rebuilds

On any edit, the rebuild starts at the first step you changed and runs forward to the end. Everything before it is reused from a cache rather than recomputed, so editing the last step of a long history is fast and editing the first one is not.

Three things never trigger a rebuild at all: renaming a step, toggling whether a sketch is shown in 3D, and moving a step in or out of a group.

A change to a named parameter is the exception: it rebuilds from the very first step. Named Parameters explains what that costs and why it is still the right way to work.

Committing, cancelling, undoing

The footer of the panel carries the buttons that end the step. On a step you have only just created they read Cancel and OK. On a step you are revisiting there are three: Delete on the left, then Cancel and OK together on the right. On a sketch the right-hand button reads Finish Sketch.

Enter is OK and Esc is Cancel, on both kinds of step:

• On a step you just added, Cancel removes it, exactly as it always did.
• On a step you are revisiting, Cancel puts it back to what it was the moment you opened the panel, and files no undo entry of its own. The net effect is as if you had never opened it, so the next Ctrl+Z reaches whatever you did before the edit rather than undoing the edit you already took back.

Two things get the keystroke before the step does, and both are what you would want. A field you are typing in keeps its own Enter and Esc, so an expression editor commits or reverts without closing anything behind it. And a picker filling one of the step's fields owns Esc — the first press ends the pick, the second cancels the step. The one exception is a brand-new step: there Esc discards it wherever the focus happens to be, because in a step you have just added it means "I did not want this", not "revert this field".

Clicking outside the panel closes it and keeps the edits, the same as OK: your changes went into the model as you typed them, so there is no separate moment of committing. If what you wanted was to back out, use Cancel or Esc rather than clicking away.

Most of the screen does not count as outside. Clicks in the 3D viewport are excluded, as are clicks in the SmartObjects panel, the picking banner, a dropdown and anything floating above the page. Otherwise you could not pick a face without losing the panel that asked for it. Inside a sketch the rule is switched off altogether: clicking in the viewport is how you draw, so it never closes the panel, and neither does clicking the page around it. Press Finish Sketch to come out.

The whole span from opening the panel to closing it is one undo entry, named Edit followed by the step's name. Ten adjustments to a depth while the panel is open collapse into one undo, so a single Ctrl+Z puts the step back the way you found it.

Undo and redo wait for the rebuild the action set off to settle before they record anything, so what comes back is the finished document rather than a half-regenerated one. It costs a moment on a heavy part and it is why redo brings back a body rather than an empty step.

Renaming a step

Click the name in the panel header and type. A step called Extrude 4 tells you nothing six weeks later; Mounting boss tells you what it is for. Renaming never rebuilds anything.

Turning a step off instead of deleting it

Right-click a pill and choose Disable. The rebuild skips that step entirely, as if it had never been added, and everything downstream rebuilds without it. Right-click again and choose Enable to bring it back.

This is the right tool for "does anything still depend on this?" and for a variant you want to keep in the file. Disable the step, look at what turns red, and enable it again.

Sketches are not on this menu. A sketch is suppressed by the feature that consumes it, never by hand, so there is no Disable on a sketch's pill. What you usually want there is Hide in 3D, which takes the drawing off the screen and changes nothing about the model.

The pill goes inert while it is off, which catches everyone once. Reading the Timeline has the states and how to tell them apart.

Deleting a step

Delete in the panel footer, or Delete in the pill's right-click menu.

A deletion that would break something asks first, whatever kind of step it is. Not just sketches and reference geometry: a chamfer whose edges were born in the cut you are deleting is a dependent too, and so is a fillet on a face a boolean made. The check walks the references of every step in the document, through the bodies as well as through the picks, and if it finds any you get a dialog headed Delete {name}?, the sentence {count} features are built on it: and the list of their names.

It then offers the two honest outcomes, and a way out of both:

• Delete only {name} — the step goes and those features turn red until you re-pick their inputs.
• Delete all {n} — the step and everything built on it go together. With a single dependent the button reads Delete both.
• Cancel — nothing happens.

Nothing is built on the step? Then there is no dialog: it goes straight away, in one undo entry.

The same guard covers geometry inside a sketch. Delete a line that is one side of an extruded profile, the arc a sweep follows or the line a revolve turns around, and you get the same dialog worded for a selection rather than for a step.

Deleting a step also deletes, silently, any group it leaves empty.

Several steps at once

Shift-click pills to build a multi-selection, then right-click it.

Disable and Enable appear only when every step in the selection is already in the same state, so a mixed selection offers neither. Sketches stay out of the count and out of the toggle, so a selection that mixes a sketch with the features around it still offers the entry — and applies it to the features alone. Group has conditions of its own, which Reading the Timeline sets out.

When it goes wrong

The panel will not close. Esc went somewhere else: to the field you are typing in, or to a picker that is filling one of the step's inputs. Press it again, or press Enter and click OK. In a sketch neither key closes anything at all: the way out is Finish Sketch.

Esc took back more than you meant. On an existing step Esc is Cancel, and Cancel reverts everything you did since the panel opened, not the last thing you typed. It is one gesture, not a stack. If you wanted to keep most of the edit, close with OK and fix the one value.

A step refuses to be deleted and says nothing. The base sketch of a smart object cannot be deleted. There is no dialog and no message: the click has no effect. Delete the smart-object step instead.

Steps went red after an edit you thought was small. Something downstream was pointing at a face or an edge that your change moved too far, or removed. Open the red step and read its banner. When a Step Goes Red groups the messages, and References That Survive an Edit explains how far a face can move before a downstream fillet loses it.

See also

• Reading the Timeline: what the pills and their colours are telling you
• When a Step Goes Red: reading the banner in a failed step
• References That Survive an Edit: why a downstream step loses the face it was pointing at
• Named Parameters: putting the number in one place instead of in the step