Rebuilds and speed

Two different pieces of work

Editing a dimension does two things, and they cost very differently.

The solve. Re-running the constraint solver over the sketch. Fast: well under a millisecond on a typical sketch, and it stays fast as sketches grow.

The rebuild. Rebuilding the solid from every feature in order. Slower, and its cost depends entirely on what the features are. Tens of milliseconds for straight-sided geometry, seconds for some curved geometry.

The activity row reports both separately, which is exactly the diagnostic you want when something feels sluggish: it tells you which half is costing the time.

The stages

While rebuilding, the activity row names the stage:

Stage	What is happening
boot	Getting the modelling machinery ready
parts	Building each feature's own shape
body	Folding them all into one solid

body is where booleans happen and where nearly all the time goes.

Past four seconds the row turns amber. That is a hint that something is unusually expensive, and the stage name says where.

Why curved cuts are slow

A rectangular pocket is a handful of flat faces. A round pocket is a many-sided prism, and every one of those sides has to be intersected against the material.

The difference is not marginal. A round pocket costs roughly a hundred times a square one, and a round hole all the way through a part can take seconds where the square equivalent is instant.

If a document is slow, curved cuts are almost always why. Some practical consequences:

• A part with several round holes is noticeably heavier than the same part with slots.
• Opening a saved document is slow if the document is slow, because the solid is rebuilt from the features rather than stored. See saved files.
• The cost is per rebuild, so it is paid again on every dimension edit.

Nothing blocks

The rebuild runs alongside the interface rather than freezing it. You can keep drawing while the solid catches up.

Only one rebuild runs at a time, and a newer request supersedes an older one. Dragging a dimension field through ten values does not queue ten rebuilds; the last one wins.

While a heavy fold is in flight you may briefly see the individual features drawn separately rather than the finished solid. That is intentional: a usable picture beats an empty viewport. It settles as soon as the fold lands.

When it does not come back

Occasionally, on a stack of features with curved tools, the modelling kernel fails in a way it cannot recover from.

The tool notices. If the kernel goes silent for thirty seconds it is restarted, and you get a message naming the stage it died in. The input that caused it is dropped rather than resent, so it does not immediately fail again.

After three restarts it stops trying and asks you to reload the page.

This is uncommon, and it clusters on multi-feature parts with curved cuts. If you hit it repeatedly on one part, the workaround is to simplify the offending feature: a slot instead of a round hole, or the same cut made as two simpler ones.

Reading the errors

Where	Message	Meaning
Timeline, red	Rebuild failed	The whole rebuild failed. The last solid that built stays on screen, ghosted, and takes no picks
Timeline, amber	Body build	The fold failed but the pieces drew. You are seeing parts, not the finished solid
Timeline	The kernel stopped responding	A restart happened. Try the edit again

A Body build message often names a specific refusal, such as a holed cut reaching the far side of the body, or a new base body overlapping existing material.

The difference matters for what you can do next. A Body build failure leaves you looking at geometry the kernel has just built, so it still answers to the mouse. A Rebuild failed leaves you looking at the previous model, which the document no longer describes, so it does not.

Keeping it quick

• Prefer straight-sided cuts where the part allows it.
• Put curved features late, so earlier edits rebuild against less.
• Watch the two numbers in the activity row. If the solve is the slow one, the sketch has too much in it; if the build is, the solid does.

See also

• The status foot
• Profiles, for why curves cost what they do
• What it will not do