When a molecular model contains several selected atoms, changing their coordinates can feel risky: will the whole group move together, or will every atom be placed at the same position? In SAMSON, the Inspector’s Relative option is the key to understanding that difference.
This matters whenever you want to adjust a group of atoms while keeping its internal arrangement intact. The Inspector lets you edit attributes for selected nodes, but the result depends on both what is selected and how the position edit is configured. A quick check before typing can save you from an unexpected change to the structure.
First, know what the Inspector is showing
Select the atoms you want to work with, then open the Inspector from Interface > Inspector, with Ctrl+2 on Windows or Linux, or Cmd+2 on Mac. You can also open it from the selection’s context toolbar.
Attributes are organized by node type and attribute group. If several atoms are selected, the Inspector displays the attribute values of the last-selected atom of that type. That means the position you see is not necessarily a summary of every selected atom’s position. It is the value for one selected atom.
At the same time, changing an attribute in the Inspector changes that attribute for all selected nodes of the same type. So if you have multiple atoms selected and edit their position, the edit applies across the selected atoms. Keep this distinction in mind: the displayed value comes from the last-selected atom, while the edit affects the selected atoms of that type.
The Relative setting determines the outcome
With multiple atoms selected, the Relative option controls how a position change is applied. If it is on, you can change the group’s position while preserving the relative positions of the atoms inside the group. In practical terms, the atoms move as a group rather than being assigned one shared position.
If Relative is unchecked, the selected atoms’ positions are changed to the same value. For a group of atoms, that can remove the spatial separation you intended to preserve. Before editing coordinates, check that the option is on if your goal is to move the group without changing its internal arrangement.
A careful workflow for editing a group
- Select the intended atoms. Check that the selection contains the group you mean to edit. The Inspector can show attributes for different node types depending on what is selected.
- Open the Inspector and find Position. If the panel contains many attributes, type
positioninto its filter to narrow the list. - Check Relative before changing coordinates. Leave it enabled when you want the group to move without changing the atoms’ relative positions.
- Make the edit and inspect the result. Look at the structure after the change, rather than assuming the displayed position represents every atom in the selection.
Filtering is especially useful when you are working with a long attribute list: it helps you get directly to the property you need without changing the selection. The Inspector can also edit other attributes, though some values are not modifiable. For example, an atom’s atomic weight, element name, and symbol depend on its element type; changing the element type updates those dependent attributes.
When an edit does not look right
If several atoms end up at the same position, check whether Relative was unchecked. If the change affected more atoms than expected, review the selection and remember that edits apply to all selected nodes of the same type. SAMSON’s history mechanism lets you undo changes, which is useful when testing how an Inspector setting affects a selection.
The central habit is simple: confirm the selection, find the attribute, and check the edit mode before changing coordinates. That small pause makes multi-atom edits easier to reason about—and helps protect the geometry you meant to keep.
For more details, see the SAMSON Inspector documentation.
Note: SAMSON and all SAMSON Extensions are free for non-commercial use. Get SAMSON.