A distance or angle can be easy to read once and surprisingly easy to lose track of later. You may adjust a structure, change the view, and then wonder whether the number on screen is still current—or whether you saved it at all. A reliable measurement workflow should make it clear what you are measuring, keep values current as atoms move, and preserve the annotations you want to revisit.
In SAMSON, the Measure editor handles bond lengths, distances, angles, and torsions. Open it from the left-side menu in the viewport, or use Ctrl+M on Windows/Linux or Cmd+M on macOS. Then choose the measurement by clicking the relevant structure elements:
- Click a bond to show its length.
- Click two atoms to show the distance between them.
- Click three atoms to show the angle.
- Click four atoms to show the torsion.
The key distinction is whether a measurement is temporary or saved. A measurement that has not been saved appears as a temporary annotation. It remains visible regardless of zoom, which is useful for a quick check while working, but only one temporary measurement can exist at a time. Making another measurement replaces it.
To keep a measurement, press Enter. SAMSON saves it as a label in the document. This is useful when you want to compare several measurements, return to them later, or keep them with the structure. If you save the document as a SAMSON .sam or .samx file, measurement labels are saved too.
Let the measurement follow the structure
When the atoms associated with a saved measurement change position, SAMSON automatically updates the measurement. This applies in the viewport, Document view, and Inspector. Measurements also update when associated atoms change charge. That makes saved annotations useful during tasks such as moving atoms or interactive minimization: the displayed value follows the modeled structure instead of remaining a stale number from an earlier configuration.
Inspect what a saved distance tells you
A saved measurement label can provide more than the value drawn beside the structure. Select the label and open the Inspector to access the atoms associated with it. For an atom-to-atom distance, the Inspector also shows additional measurements for projections on planes. These can help you examine the same relationship from more than one geometric perspective, rather than relying on the single displayed distance alone.
Make saved annotations easier to read
Saved measurements behave like other labels: their visibility can depend on zoom level, and their font, color, and offset can be adjusted. In the Inspector, measurement labels also let you change the colors of distance lines and angle planes. If a color change is no longer useful, you can restore defaults: double-click the associated color text to reset line or angle colors, or use the clear button next to Text color to reset the text color.
For consistent numeric precision, check Preferences > Rendering > Labels. There you can set the number of decimal places used for angles and distances created with the Measure editor. The same preferences provide a font for labels that do not have an individually specified font; a label’s font can also be set directly in the Inspector.
A practical habit is to use temporary measurements for quick checks, press Enter for values worth keeping, and inspect saved labels when you need to revisit their associated atoms or properties. For instructions and related details, see the SAMSON measuring documentation.
Note: SAMSON and all SAMSON Extensions are free for non-commercial use. Get SAMSON.