A distance or angle can look correct in one snapshot and change as soon as you move atoms or minimize a structure. That makes it easy to lose track of whether a geometric feature is still what you intended to inspect. In SAMSON, the Measure editor can show measurements as you work—and saved measurement labels can update along with the atoms they refer to.
Choose the measurement that answers your question
Open the Measure editor from the left-side menu in the viewport, or use Ctrl+M on Windows/Linux or Cmd+M on macOS. Then select the relevant part of the structure:
- Click a bond to toggle its length.
- Click two atoms to display the distance between them.
- Click three atoms to display the angle between them.
- Click four atoms to display the torsion between them.
This is useful when a visual estimate is not enough: a labeled value gives you a concrete measurement to inspect while editing the model.
Temporary check or measurement you can keep?
By default, a measurement is temporary. It stays visible regardless of zoom level, but disappears when you make the next measurement. Only one temporary measurement can be shown at a time. This is convenient for a quick check, but it is not the right choice if you want to preserve several observations.
To keep a measurement, press Enter after displaying it. SAMSON saves it as a label in the document. You can repeat this for additional measurements, so multiple annotations can remain available together. If you save the document in a SAMSON format (.sam or .samx), measurement labels are saved with it.
Follow geometry while the structure changes
A saved measurement is associated with the atoms used to create it. When those atoms change position or charge, the measurement is automatically updated in the viewport, document view, and Inspector. This lets you follow a distance, angle, or other measurement while using Move editors or interactive minimization, instead of relying on an old value or repeatedly recreating the annotation.
For a saved label, you can select it and open the Inspector to access the associated atoms and measurement information. Atom-to-atom distance labels also show additional measurements for projections on planes in the Inspector.
Make annotations readable, not distracting
Saved measurement labels behave like other labels: their visibility depends on zoom level, and their font, color, and offset can be adjusted. For measurement labels, the Inspector also lets you change the color of distance lines and angle planes. If a color change is no longer useful, you can reset line or angle-related colors by double-clicking the associated text in the Inspector. Use the X button next to Text color to reset the text color.
You can set the font for an individual label in the Inspector. For labels without an individually specified font, preferences under Rendering > Labels control the default. Those preferences also let you set the number of decimal places displayed for angles and distances created with the Measure editor.
A simple workflow for model review
- Use a temporary measurement for a quick inspection.
- Press Enter to preserve measurements you want to compare or revisit.
- Move atoms or run interactive minimization and watch the saved values update.
- Adjust label appearance and decimal places when annotations are difficult to read.
- Save the document as
.samor.samxto retain its measurement labels.
This workflow helps separate a fleeting visual check from a measurement that belongs in the model record. For details on measuring and editing annotations, see the SAMSON measuring documentation.
Note: SAMSON and all SAMSON Extensions are free for non-commercial use. Get SAMSON.