Estimate Ring Size

Estimate Ring Size

Estimate Ring Size answers a question you get every time a model arrives from somewhere else: what size is this ring? It measures the hole the finger goes through, converts that diameter into a finger size in your sizing standard, and drops a Ring Curve at that size so the rest of RhinoArtisan knows what it is working with.

It is the command to run on an imported STL, a model a customer sent over, or a ring you modelled long enough ago that you no longer remember the size.

How it works

The command has no panel and asks for nothing. Run it and it does all of this on its own:

• It collects every visible, unlocked object in the document — surfaces, polysurfaces and meshes alike. Hidden and locked objects are ignored, which is the simplest way to exclude a gemstone or a reference solid from the measurement.
• It cuts those objects with the two world planes that pass through the origin and looks at the resulting section curves.
• Across the X axis it finds the two sections closest to the centre — the left and right walls of the band — and the distance between them is the estimated inner diameter.
• It scores how ring-like the result is: whether it found walls on both sides, whether it found a floor below the axis, whether the diameter falls in a plausible range, and how symmetric the two walls are around the centre.
• If the score is high enough, it converts the diameter into a finger size and adds the matching Ring Curve to the document.

What it reports

The result is written to the Rhino command line, not to a dialog. You get one of two answers:

• The probability of this being a ring is 95% and Estimated finger size: … — followed by the size, its diameter in millimetres, and the standard it was read in. A Ring Curve at that size appears in the viewport and in the Outliner.
• I don't think this is a ring. — nothing was measurable, or what was measured did not look like a band. Nothing is added to the document.

The percentage is a confidence figure, not a tolerance: it tells you how convinced the command is that it was looking at a ring, not how accurate the diameter is.

The sizing standard

The size is expressed in the standard of the ring size currently set in your session — the one you pick in the Size section of any shank command. If none has been set yet, the command falls back to USA. Change your working standard first if you want the answer in Europe, UK or Japan sizes.

Getting a reliable reading

The measurement assumes the ring is modelled the way RhinoArtisan builds them: centred on the world origin, with the finger axis along Y. Two consequences worth knowing:

• An imported model sitting away from the origin will not measure correctly. Move it to the origin first.
• The command measures the narrowest opening it finds. Anything crossing the finger space — a lower rail left long, a bezel that dips inside the band — will be measured instead of the band itself and will give you a smaller size than the real one. If you get an implausibly small answer, that is usually why.