Reducing node count on a heavy path

A cut path here is smooth curves and nothing else — never a chain of short straight steps. How many curves the outline is made of is not fixed by the shape; it is decided by how tightly the cut is asked to follow the traced edge, and by how much wobble there was to follow.

First, count them

Paths in the preflight is not the number you are looking for. That counts subpaths — separate closed loops — and eight or more of them means specks are being picked up, which is a different problem.

The node count is the curve count, and it is on the tuner already — the chip under the proof that reads something like "1 path · 567 curves".

Compare two runs of the same artwork rather than looking for an absolute number. What counts as heavy depends on the cutter.

Curve fit tolerance is the direct control

It is the furthest the fitted curve may sit from the traced edge, and it ships at 0.25 mm. Tighten it and the outline has to be broken into more curves to stay inside it; loosen it and one curve covers more of the edge, so the same line comes out in fewer of them.

It is expressed in millimetres rather than in pixels, which matters more than it sounds: the same number gives the same real-world accuracy whatever the source resolution. On noisy files it is usually worth 0.45 mm.

Edge smoothing removes the wiggle first

Smoothing runs along the traced edge before any curve is fitted, and it ships at 0.5 mm. A noisy edge — JPEG ringing, a low-resolution alpha channel — is a lot of small detail the cut is obliged to follow, and every wiggle it follows is nodes.

Raise it and the edge arrives smoother, so fewer curves describe it. Raise it too far and it rounds off genuine detail, which is a worse problem than a heavy path.

Two settings that remove geometry rather than simplify it

• Opening removes appendages thinner than its radius. Hair-thin strands are expensive in nodes and produce a path no blade could follow anyway.
• Minimum area drops components below a fraction of the largest. Each speck it removes is a whole closed subpath, not just a few segments.

Both change what is cut, not just how it is written down. Reach for the fit tolerance first.

On a parametric shape

A drawn outline is cheap — a rectangle is four curves — until it is scalloped. A scalloped 42 cm panel comes to well over a thousand points, and a node at every one of them is exactly the path this guide is about.

So the scallop is fitted down to smooth curves instead, which gives the same line in a couple of hundred nodes. How far the fitted scallop may stray from the true wave is a millimetre tolerance, 0.5 mm by default, and raising it means fewer nodes. It is set from the command line rather than on the shape screen.

What not to do

Do not try to reduce nodes by re-issuing the file at a different size. Scaling a finished file multiplies every millimetre setting that was baked into it, so a resize is not a re-trace and cannot be tuned like one. If the path has to be right at a new size, trace the artwork again.