A distance or angle can be easy to read while you are inspecting a structure—and easy to lose track of a moment later. You move an atom, adjust a conformation, or zoom in to examine a detail, and suddenly the number you noted no longer describes the structure in front of you. In SAMSON, the Measure editor helps you inspect geometry and keep saved measurements connected to the atoms they describe.
Use the editor from the left-side menu in the viewport, or open it with Ctrl+M on Windows/Linux or Cmd+M on macOS. Then click the structural features you want to measure:
- Click a bond to show its length.
- Click two atoms to show the distance between them.
- Click three atoms to show an angle.
- Click four atoms to show a torsion.
The important workflow choice comes next: should this be a quick, temporary reading, or an annotation you want to keep?
Temporary reading or saved annotation?
A measurement that you have not saved is temporary. It remains visible regardless of zoom level, which is handy when you are checking a value as you work. But it disappears when you make another measurement, and only one temporary measurement can be displayed at a time.
To keep a measurement, press Enter. SAMSON saves it in the document as a label. You can then make additional measurements without replacing the saved one, and the label remains part of the document. Save the document in a SAMSON format (.sam or .samx) to preserve measurement labels with it.
This distinction is useful during model review: use a temporary measurement for a quick check, and save measurements that you expect to revisit, compare, or share as part of the document.
Let the measurement follow the structure
A saved measurement is not merely a number written beside the model. It is associated with the atoms used to create it. When those atoms change position—or their charges change for charge-related measurements—SAMSON automatically updates measurements in the viewport, Document view, and Inspector.
That makes saved measurements useful while editing: you can move atoms or use interactive minimization and watch the displayed geometry respond, rather than relying on a value recorded before the structure changed. The annotation gives you a continuing reference to the atoms involved.
Inspect what a saved measurement refers to
If you need to check which atoms are behind an annotation, select its label and open the Inspector. The Inspector shows a Measure group for the selected measurement. For a saved atom-to-atom distance, it also provides measurements for projections on planes. This can help when a single distance is not the only geometric detail you want to examine.
Saved labels can be formatted like other labels: their visibility depends on zoom level, and you can adjust their font, color, and offset. For measurement labels, the Inspector also lets you change the color of distance lines, angle planes, and planes. If you want to return a line or angle color to its default, double-click the associated color text in the Inspector. To reset text color, use the clear button beside Text color.
Font settings can be changed on an individual label in the Inspector. For labels without an individual font setting, use Preferences > Rendering > Labels. That preferences area also controls the number of decimal places displayed for angles and distances created with the Measure editor.
A practical measuring routine
- Open the Measure editor and click the bond or atoms that define the geometry you want to check.
- Use the temporary display for a quick, one-off inspection.
- Press Enter when the measurement should stay in the document.
- After moving atoms or minimizing the structure, check the updated measurement in the viewport or Inspector.
- Adjust label appearance or decimal-place preferences if clearer presentation is needed.
- Save the document as
.samor.samxto retain its measurement labels.
For more details, see the SAMSON measuring documentation.
Note: SAMSON and all SAMSON Extensions are free for non-commercial use. Get SAMSON at samson-connect.net.