Measurement forms
The few numbers you measure, the formulas that turn them into the model, and how to tell your agent a value is wrong.
What a measurement form is
A measurement form lists the handful of numbers you can measure on a device, such as the case width, the wall thickness or the spacing between ports. Formulas turn those numbers into every size and position in the model, for example body.w = case_w - 2*wall, or the position of each of several ports as margin + i*pitch.
Your AI agent usually builds the form for you from what it knows about the device. You can then:
- see every formula and which parts of the model each measurement feeds;
- change a value and watch the 3D model update straight away;
- flag a value or a formula as wrong, with a note, for your agent to fix.
In the modeler
When a device has a form, the Measurements panel appears next to the 3D model. For each measurement it shows:
- its value and unit (mm, count, degrees or grams);
- its source: measured, datasheet or estimate;
- how to measure it;
- the fields it feeds, with their formulas and results;
- any error, such as a value outside its range or a size that would come out negative.
Change a value and the model re-renders after a short pause. The change saves automatically and shows in your other open browsers, like any edit.
A value worked out from others counts as the least certain of its inputs. For example, a size worked out from one measured value and one estimate is marked as an estimate.
In the chat
Clients that support MCP Apps, including Claude (web and desktop) and ChatGPT, show the form inside the chat. You can edit values or flag them there, and the changes reach your draft and any open modeler at once. Other clients show the same form as text.
When something is wrong
Press the flag button next to a value or formula and say what's wrong, e.g. "the gap is 24 mm, not 16". Your agent sees open flags in every answer. It fixes each one, then resolves it with a note on what it changed, and you see that note next to the value.
Every answer to your agent also includes automatic checks:
- a part bigger than the face it sits on;
- an opening that runs over the edge of its face;
- a value that looks 25.4 times too big (inches converted to millimetres twice) or 10 times off.
Formulas can use + - * / ( ), min, max, round, abs and measurement names. Units are checked, so adding millimetres to a count is refused.