Calibrate

Once a calibration is saved, the rule reads in real units anywhere on the model and the export buttons come alive. Selecting the tool on an uncalibrated model opens the Calibrate window by itself, and a calibrated model is ready to go.

Option bar

• Calibrate - Opens and closes the Calibrate window, and stays lit while it is open. Closing it this way counts as backing out, and reverts.
• Clear - Throws the calibration away and goes back to raw model units. Exports go back to raw units with it. The button appears once there is a calibration to clear.
• File - Which file to write at real size. STL in millimeters, the unit every slicer assumes, geometry only. GLB in meters, per the glTF spec, painted color included. FBX in centimeters, with the unit stated inside the file so the scale can be checked, geometry only.
• Export - Writes the model at real size in the chosen format. It comes alive once you have calibrated, so every file it writes is at a size you have confirmed. The model on screen is never resized.

The format picker stays live even while Export is dimmed.

The Calibrate window

• 1. What is the rule laid across? - A list of known objects, the same specification sizes Gradus Adeptus uses, plus Custom length. Beside it, the real length in millimeters. Typing in the field switches the choice above to Custom length.
• 2. Lay the rule along it. - No control: the rule follows the window, so open means visible. Drag either end onto the two edges of the known span.
• Snap to mesh - Off by default, which lets each end move freely anywhere in the viewport. Turn it on to make a dragged end land on the visible mesh surface. If a snapped drag hits nothing, the end stays exactly where it was.
• Save - Takes the rule's current span to be the length above, and sets the export scale to match. The model on screen is never resized.

Notes

• Save is the only way out of the window that keeps anything. The close box, Escape, a tool switch and the toolbar's own Calibrate button all revert.
• Save does both jobs at once: it fixes the calibration and sets the export scale. Clear throws both away together.
• Dragging the rule never calibrates. Calibrating is a deliberate button press.
• Everything is stored in millimeters. The Settings, UNITS metric or imperial toggle changes what you read. Stored numbers and the three export formats keep their own fixed units, so a file always comes out right.