Precisely positioning atoms, molecules, or custom structures in 3D space is a common task in molecular modeling. But anyone who has tried to reposition a molecule just right—whether to match experimental data, prepare for simulations, or maintain symmetry—knows it’s a subtle art. SAMSON provides a set of intuitive tools known as move editors to make this process precise, visual, and interactive.
In this post, we’ll walk through how to use the Local Move Editor to rotate and translate molecular fragments in your viewport, with or without snapping. This isn’t just a user manual—it’s a workflow solution to help you stop struggling with manual adjustments and start refining molecular structures with confidence.
Why precise object movement matters
Whether you’re building a crystal unit cell, forming complexes, or arranging fragments for docking studies, reliable movement tools save a great deal of time. The Local Move Editor gives you intuitive ways to translate or rotate along the selected object’s principal axes—and offers snapping and numeric inputs for control.
Getting started with the Local Move Editor
First, select the atoms or fragments you’d like to move. You can use the rectangle selection editor for this.
Translation in the camera plane
To start translating your selected atoms within the plane of the screen:
- Select the Local Move Editor by pressing M.
- Click and drag the central translation widget (the cross-arrow) to move the selection interactively.
If you want to translate in fixed steps (e.g., 0.5 Å):
- Enable snapping in the top-left of the viewport.
- Set your step size under Preferences > Editors > Snapping.
Rotating around axes or freely
Rotations work similarly. Click and drag one of the curvature arrows (rotation widgets) to rotate along one of the principal axes, or use the trackball (the sphere) widget to rotate in any direction.
Want your rotation to snap to specific angles (e.g., 10° steps)? Turn on snapping in the same viewport menu.
Pro tips
- You can right-click on a widget (or Ctrl/Cmd + click) to specify exact translation or rotation parameters.
- All actions are undoable. Use Edit > Undo if the outcome isn’t as expected.
- Need to rotate around a specific pivot? You can control the pivot point for even more precise movement.
Why it’s worth mastering
A well-placed molecule isn’t just aesthetically pleasing—it determines the correctness of downstream calculations and interpretation. Whether you’re preparing a publication figure or modeling a molecular mechanism, the Local Move Editor offers the clarity and control you need right within the interactive viewport.
To explore even more movement tools like the Global Move Editor or Displacer, check the original documentation page at https://documentation.samson-connect.net/users/latest/moving-objects/.
Note: SAMSON and all SAMSON Extensions are free for non-commercial use. You can get SAMSON at https://www.samson-connect.net.