A distance or angle can look clear at one moment and become hard to trust after you move or refine a structure. Was the value recorded before or after the change? Is the annotation still attached to the atoms you intended? In SAMSON, the Measure editor helps you inspect molecular geometry and keep saved measurements connected to the atoms they describe.
Start with the geometry you need. Open the Measure editor from the left-side menu in the viewport, or use Ctrl/Cmd + M. Then click the relevant feature:
- Click a bond to show or hide its length.
- Click two atoms to measure the distance between them.
- Click three atoms to measure an angle.
- Click four atoms to measure a torsion.
For an angle or torsion, choose the atoms that define the geometry you want to inspect. The measurement is a quick way to check a local feature without needing to estimate it visually from the viewport.
Temporary check or saved record? A new measurement is temporary until you press Enter. That can be convenient when you are checking one value at a time: the temporary measurement stays visible regardless of zoom, but disappears when you make the next measurement. Only one temporary measurement can be shown at once.
If you want to keep several values visible, or revisit them later, press Enter to save each measurement as a label in the document. Saved labels can be selected, inspected, and adjusted like other labels. If you save the document in SAMSON’s .sam or .samx format, the measurement labels are saved with it.
Keep measurements useful while editing. Saved measurements update automatically when their associated atoms change position or charge. This lets you follow geometry while using Move editors or interactive minimization, rather than repeatedly measuring and comparing values by hand.
The example below shows the Measure editor in use:
Inspect the detail behind a distance. Select a saved measurement label and open the Inspector to see its associated atoms and measurement properties. For an atom-to-atom distance label, the Inspector also shows additional measurements for projections on the planes. Those values can help when a single overall distance does not tell you enough about how two atoms are positioned relative to the structure.
Make saved annotations readable. Measurement labels follow the usual label behavior: their visibility can vary with zoom, and their font, text color, and offset can be adjusted. In the Inspector, you can also change the color of distance lines and angle planes. To return a line or angle color to its default, double-click the associated text in the Inspector; to reset the text color, use the clear button beside Text color. If you need consistent formatting across labels, set a font for an individual label in the Inspector or adjust the default label font and displayed decimal places in Preferences > Rendering > Labels.
A practical workflow is to measure the feature you want to monitor, press Enter if you need to keep it, then make the structural change and watch the annotation update. Save the document when you want those labels to remain part of the project. This turns measurements from one-off readings into a record you can inspect as the model changes.
For more details, see the SAMSON measuring documentation.
Note: SAMSON and all SAMSON Extensions are free for non-commercial use. Get SAMSON.