v_ase
v_ase brings ASE's convenient terminal and Python workflow together with
direct, Blender-style 3D structure editing. Open a structure or trajectory
with one command, inspect and measure it in a local browser, modify atoms when
needed, and export publication or CAD-ready results.
This is an actual v_ase editing sequence, not playback of a finished model. Each selection boundary advances by one puckered phosphorene ridge. Small Selection-COM rotations accumulate from the fixed first ridge to the 36 degree H-APNR target tabulated in the cited study.
| Work directly in v_ase | Included |
|---|---|
| Structures and trajectories | ASE-supported formats, live timeline, per-frame bonds |
| Geometry editing | Ordered selection, G move, R rotate, axis locks, numeric input |
| Scientific inspection | Distances, angles, torsions, displacement vectors, constraints |
| Figure preparation | Appearance, bonds, lighting, exact preview, image/video export |
| Reproducible sessions | Self-contained .vase projects and reusable visual settings |
| Agent workflows | Semantic state/command API and a vendor-neutral AI skill |
Quick Start
Install from PyPI:
python -m pip install v_ase-gui
Or install the current GitHub source:
git clone https://github.com/lgyEthan/v_ase.git
cd v_ase
python -m pip install -e .
Start an empty workspace or open a file:
v_ase gui
v_ase gui FILE
Examples:
v_ase gui POSCAR
v_ase gui trajectory.extxyz
v_ase gui relaxation.traj
v_ase gui project.vase
The default View mode is optimized for visualization, trajectories, measurement, appearance, bonds, supercells, and export. Use the top-bar mode switch or start directly in Edit when atomic coordinates must change:
v_ase gui structure.vasp --interactive
No Node.js installation or hosted account is required. Closing the v_ase browser document releases the blocking terminal process.
Everyday Workflow
| Goal | Action |
|---|---|
| Inspect a structure | Middle-drag to orbit, wheel to zoom, left-click to select |
| Edit coordinates | Enter Edit, select atoms, press Esc to focus the viewport, then use G or R |
| Measure geometry | Select 2, 3, or 4 atoms in the required order |
| Play a trajectory | Use the bottom timeline or Space; FPS and Skip update live |
| Style a figure | Use Structure > Appearance/Bonding and View |
| Repeat or wrap a cell | Use Structure > Cell & Replication |
| Save the whole session | Use Export > Save Project to create a self-contained .vase |
| Reuse only the visual style | Use Export > Save Settings |
| Hand the scene to an AI | Launch with --for-ai and provide the bundled agent skill |
Viewport tip: after selecting atoms, press
Escto close the control panel before usingGorR. The selection is preserved and keyboard focus returns to the 3D viewport.
Structure Manipulation
Use Edit when atom coordinates must change. Selection, measurement, appearance, bonds, replication, wrapping, visual translation, and export remain available in the default View mode.
Select
- Left-click selects one atom;
Shift+ click extends or removes selection. - Left-drag draws a visible selection box.
- Appearance rows select complete label groups without merging distinct labels.
- Ordered single-atom selections are retained for geometry measurement.
Move
Press G after selecting atoms. Lock the move with X, Y, or Z, type an
exact displacement in angstrom, then confirm with left-click or Enter.
Configured ASE constraints remain authoritative when Apply constraints is
enabled.
Rotate
Press R after selecting atoms. Choose Selection COM, Origin, or
Unit-cell center as the pivot, lock an axis if needed, and enter an exact
angle. Every active rotation shows:
- the rotation axis through the chosen pivot;
- a neutral line fixed at the direction where the operation started;
- an amber line that follows the current structure;
- cyan candidate lines only when the commensurate guide is enabled.
Ferrocene: Choose The Pivot
The upper cyclopentadienyl ring is selected while the Fe atom remains unselected. Rotate pivot = Origin places the rotation axis through Fe, so the animated ring rotates around a chemically meaningful external center rather than around its own center of mass.
Phosphorene: Build The Twist One Edit At A Time
The animation records a sequence of normal v_ase edits:
- Keep the first puckered ridge fixed and select the next ridge through the end of the ribbon.
- Use Selection COM, press
R, lockX, enter1.714, and confirm. - Start from the edited coordinates and advance the selection boundary by one ridge. After 21 edits, the final ridge is rotated by exactly 36 degrees.
The yellow outline always identifies the atoms affected by the current step. Bonds update while the selected tail moves, so the accumulating deformation is visible rather than replaced by playback of a prebuilt final structure.
Black phosphorene has two puckered sublayers in one armchair unit cell. The example therefore uses one half-cell ridge per step (6 atoms at this ribbon width), rather than rotating both ridges together. Green and purple distinguish the upper and lower P sublayers; both remain phosphorus in the ASE structure.
The relaxed source coordinates come from the supporting information of Villegas et al.. The 36 degree target is the largest H-APNR angle tabulated by Jang et al., and the green/purple sublayer convention follows published phosphorene structure diagrams such as Zhang et al.. The sequence is a deterministic v_ase editing demonstration. It uses the paper's target angle, but it is not the paper's periodic DFT cell or an energy-minimized nanoribbon.
Graphene/hBN: Find A Commensurate Rotation
Select the hBN layer, enable Commensurate guide, then use R, Z. The
top view intentionally hides the world X/Y/Z axes so the neutral start line,
amber current line, and labeled cyan cell-match candidates remain distinct.
Magnetic angle snap can pull the active rotation to a candidate within the
configured tolerance.
Normal R rotates selected atoms. Cell Transform is a separate periodic
operation that applies an integer matrix to the cell and every trajectory
frame. Its equations and assumptions are documented in
unit_cell_aware_rotate.md.
Measurement And Analysis
The numbered a1 to a4 markers record selection order; they are deliberately
different from atom indices.
| Ordered selection | Reported result |
|---|---|
| 1 atom | Label, element, position, force, charge, tag, magnetic moment |
| 2 atoms | Direct distance and minimum-image distance |
| 3 atoms | Angle a1-a2-a3, centered on a2 |
| 4 atoms | Signed torsion a1-a2-a3-a4 |
| 5 or more | Total count and per-label counts |
The connector, angle arc, torsion axis, and compact value badge stay attached to the selected atoms. Hover information is independent, so moving the pointer does not replace a saved measurement.
For trajectories, Analysis > Displacement compares the current frame with the previous frame or a chosen reference. Minimum-image correction, vector scale, thickness, color, and 2D/3D style are configurable. Displayed supercells repeat the vectors, and visual translation moves both endpoints without changing the physical displacement.
Constraints
ASE remains authoritative when Apply constraints is enabled. Constraint visualization is local to each atom rather than merged at a group center.
FixedLine
A compact cyan collar and local axis remain visible without selection. During
G, ASE restricts the atom to that line.
v_ase gui examples/readme_scene_assets/fixedline.traj --interactive
FixedPlane And FixScaled
Each constrained atom keeps its own local ring, crosshair, and normal marker.
When G starts, a larger translucent guide plane appears at that atom's
original position so the permitted surface remains visible while the atom
moves. Multiple selected atoms retain independent planes; no center-of-mass
plane is substituted.
VASP selective dynamics read as FixScaled are displayed from their allowed
fractional directions.
v_ase gui examples/readme_scene_assets/fixedplane.traj --interactive
FixAtoms
Fixed atoms keep their element color but use a distinct constrained surface treatment. They remain identifiable without looking selected.
Hookean
Hookean constraints show their inactive cutoff and engaged state separately.
After the constrained distance passes rt, a shaded 3D helical spring appears
between the constrained atoms.
v_ase gui examples/readme_scene_assets/hookean.traj --interactive
Relaxation
Structure > Relaxation places every optimization step on a dedicated timeline. A single loaded structure gains a relaxation movie after the first run. If a source trajectory is already open, source and relaxation timelines remain separate and the active timeline is clearly selected.
The included example starts from a deliberately compressed C60 geometry and runs ASE FIRE with v_ase's repulsive fallback calculator:
v_ase gui examples/readme_scene_assets/crowded_c60_initial.cif --interactive
The fallback calculator is intended for removing obvious close contacts, not for predictive chemistry. Its cutoff scale and strength are editable. Attach a scientific ASE calculator when the optimized energy or forces will be used as physical results.
Trajectories
Multi-frame inputs add a timeline below the viewport. Scrubbing updates the
frame continuously, selected atom indices persist when topology permits, FPS
changes apply during playback, and Skip advances by skip + 1 source
frames per tick.
Bond topology is evaluated for each frame, so bonds form or break when a pair crosses its cutoff. Appearance, pair settings, supercell display, camera, and analysis settings remain active across the movie.
Video export uses FPS as playback speed. Optional N x interpolation creates
(source_frames - 1) * N + 1 output frames. Minimum-image interpolation uses
periodic cells to avoid jumps across a boundary. Interpolation takes longer
because more frames are rendered.
Appearance, Bonds, And Rendering
Structure > Appearance controls each stable atom label:
- ASE chemical TYPE and independent visual label;
- visibility and selection availability;
- color and radius;
- Standard, Metal, or Rubber material;
- all/partial/none selection checkbox.
View mode applies appearance by label. Edit mode can keep per-atom material overrides. Relabeling does not reorder the table or merge otherwise distinct atom types accidentally.
Structure > Bonding provides automatic inference, explicit label-pair cutoffs, and manual index pairs. A pair cutoff of zero disables that pair. Changes apply immediately. Bonds support:
- cell-local or periodic minimum-image display;
- cylinder or flat 2D geometry;
- custom color or two half-bonds using the atom colors;
- configurable diameter;
- live formation and breaking during Edit transforms.
View controls projection, atomic scale, anti-aliasing, sphere smoothness, background, 2D/3D display, grid, axes, unit cell, overlays, and cell material. The Axes and Unit Cell switches update the working viewport immediately; they are not export-only settings. Hiding world axes does not remove the compact orientation gizmo. New documents use orthographic projection and a true-white background.
The top-bar renderer switches between fast modeling light and Sun/soft-shadow rendering. Sun source, target, intensity, and direction can be manipulated in the viewport and carried into Blender export.
Export And Save
| Command | Result |
|---|---|
| Export POSCAR | Current physical ASE structure in VASP format |
| Export ASE Pickle | ASE Atoms, labels, constraints, arrays, and a valid SinglePointCalculator |
| Export Image | PNG by default; JPEG, PDF, and lossless WebP from the exact preview frame |
| Export Video | Constant-frame-rate H.264 MOV or MPEG-4 AVI with optional interpolation |
| Export Blender | Optimized scene script with atoms, bonds, cell, camera, and Sun |
| Export 3DM | Instanced Rhino geometry, metadata, and saved camera views |
| Export OBJ | OBJ/MTL, camera, and metadata in a ZIP |
| Save Project | Self-contained .vase with structure/trajectory and visual state |
| Save Settings | Reusable visual settings without coordinates |
The Preview Area is the authoritative image/video frame. Its aspect ratio, camera, crop, lighting, atom scale, and included overlays match the export. Cell, grid, axes, and background can be included or excluded independently.
The system save picker is opened before expensive rendering or scene generation when the browser supports it. Canceling the picker cancels the export. Chrome may then show This site can view changes you make to this file. That message is Chrome's File System Access permission notice: v_ase can write only to the destination selected in that picker. Browser code cannot hide the notice while retaining destination selection before rendering.
Video progress covers frame rendering, upload, encoding, and the final file
write. It increases monotonically, reports an estimated remaining time, and
reaches 100% only after the output has been written. Every source frame is
retained exactly once at 1x; interpolation adds in-between frames. Visible
displacement vectors and other selected scene overlays are recalculated for
each rendered frame.
.vase is self-contained and does not reference the original input file.
Opening an ordinary structure in an existing tab keeps the current visual
settings; opening .vase restores the saved project.
Rhino export requires the optional dependency:
python -m pip install "v_ase-gui[rhino]"
OBJ export has no optional Python dependency.
AI And Agent Use
--for-ai exposes the same document through a semantic state and command API,
so an agent can inspect coordinates, cell, constraints, trajectory frames,
selection, measurements, camera, materials, lighting, and export state without
repeatedly interpreting screenshots.
v_ase gui STRUCTURE --for-ai
The startup handshake reports the human GUI URL, state and command-schema
URLs, the live window.v_aseAI browser API, and the installed agent-skill
location. A user can take over the same document in the normal GUI at any time.
Use the complete v_ase agent skill. The compatibility link skills_v_ase.md resolves to the same canonical instructions. The skill folder includes the semantic API, verified workflows, safety rules, troubleshooting, and end-to-end evaluation cases.
Clients with skill-folder support should install the complete directory:
# Codex
cp -R v_ase/skills/visualizing-atomic-structures-with-v-ase "$CODEX_HOME/skills/"
# Claude Code, from a project root
mkdir -p .claude/skills
cp -R v_ase/skills/visualizing-atomic-structures-with-v-ase .claude/skills/
For clients without a skill loader, provide SKILL.md and the relevant
one-level references/ files as context. The contract is vendor-neutral.
Documents And File Opening
The top-bar Open button starts with the operating system file picker. A selected file can:
- replace the active document;
- append structures to its current trajectory;
- open in a new independent v_ase tab.
If the active document is empty, the selected file opens there immediately; the destination chooser is shown only when a document already contains a structure or trajectory.
The + beside the document tabs creates an empty independent document. Each
tab owns its structure, trajectory, camera, selection, history, settings,
calculator, and .vase output.
Adding .vase to an existing trajectory imports only its structures and keeps
the current tab's visual state. Replacing a tab or opening a new one restores
the complete .vase project.
Python
from ase.build import molecule
from v_ase.visualize import view
atoms = molecule("H2O")
view(atoms) # View mode
Return an edited ASE object:
edited = view(atoms, viz_only=False)
print(edited.positions)
view() accepts one ASE Atoms, a sequence of frames, or a supported file
path. view_edit() remains a compatibility alias for Edit mode.
File Formats
Common inputs include POSCAR/CONTCAR, VASP files, XDATCAR, vasprun.xml,
XYZ/extxyz, ASE .traj, LAMMPS dump/data, CIF, and .vase. ASE readers cover
additional formats.
Use --format when an ambiguous filename does not identify the reader:
v_ase gui ABCD --format POSCAR
v_ase gui ABCD --format vasprun.xml
v_ase gui ABCD --format lammpstrj
v_ase gui ABCD --format data
Use --index : for every frame, --index -1 for the last frame, or an integer
for one frame.
Repeated POSCAR/CONTCAR species blocks remain separate visual labels. For
example, O Cu O with counts 1 14 5 becomes O1, Cu, and O2 while all
oxygen atoms remain ASE element O.
Controls
| Input | Action |
|---|---|
| Left click / Shift + click | Select / extend selection |
| Left drag | Box select |
| Middle drag | Orbit without inertia |
| Shift + middle drag | Pan |
| Wheel | Zoom |
G / R |
Move / rotate selected atoms |
X, Y, Z during G/R |
Lock transform axis |
X, Y, Z otherwise |
Align camera to an axis |
| Number keys | Exact move distance or rotation angle |
Enter or left click |
Confirm transform |
Esc or right click |
Cancel transform |
Ctrl+C, Ctrl+V |
Copy and paste atoms |
Ctrl+Z, Ctrl+Shift+Z |
Undo and redo structure or camera changes |
Delete / Backspace |
Delete selected atoms |
Space |
Play or pause the active timeline |
| Left / Right Arrow | Previous / next frame in the active timeline |
Tab or Esc |
Open a collapsed control panel |
Esc with the panel open |
Close it and return focus to the viewport |
The ? button contains the complete shortcut table.
Remote Servers
Install v_ase on both the local computer and remote host, then run one command locally:
v_ase gui USER@SERVER:/absolute/path/to/STRUCTURE
An SSH config alias works:
v_ase gui physics:/absolute/path/to/trajectory.extxyz
v_ase selects private ports automatically, starts the backend beside the
remote file, creates the SSH tunnel, and opens the local browser. The source
file and full trajectory cache remain on the server; only the current frame
data required for local Three.js rendering crosses the tunnel. Use ProxyJump
in ~/.ssh/config when a login node is required.
Troubleshooting
v_ase command is not found
Install and run with the same Python environment:
python -m pip install --upgrade v_ase-gui
python -m v_ase.cli --version
If the module command works but the console command does not, reactivate the
environment or add its Python scripts directory to PATH.
The browser does not open, or WSL prints gio: ... Operation not supported
The terminal also prints the complete local URL. Ctrl+click it or copy the text
beginning with http:// into Chrome, Edge, Firefox, or another browser. Keep
the terminal process running.
Example with sensitive session identifiers masked:
(base) giyeok@DESKTOP-XXXX:~$ v_ase gui
gio: http://127.0.0.1:58039/workspace?workspace_id=xxxx&session_id=xxxx: Operation not supported
For better WSL performance, keep trajectories under the Linux filesystem
rather than /mnt/c/....
A file is detected with the wrong format
Force the reader:
v_ase gui FILE --format POSCAR
v_ase gui FILE --format vasprun.xml
v_ase gui FILE --format lammpstrj
v_ase gui FILE --format data
Replicated supercell atoms cannot be selected
In Edit, displayed replicas are noneditable previews. Use Set Supercell as Cell to create real ASE atoms and an editable larger cell. In View, displayed replicas are selectable and participate in center, distance, and other measurements.
Video export is unavailable or slow
Video export requires at least two frames and browser MediaRecorder support.
MOV/AVI conversion uses the bundled imageio-ffmpeg. Interpolation renders
additional frames and requires stable atom count, element, label, and ordering
between adjacent source frames. The selected FPS controls playback time:
72 frames at 30 FPS produce 2.40 seconds. The progress indicator reaches 100%
only after encoding and the destination write both finish.
Chrome says this site can view changes made to the saved file
This is a Chrome security notice for the File System Access API. v_ase opens the system save picker before a costly image, video, Blender, or CAD export so canceling does not waste time. It receives write access only to the file you choose. Chrome does not allow a page to suppress this notice; using an ordinary browser download would remove advance destination selection.
A large trajectory opens or plays slowly
- Keep the default View mode unless editing is required.
- Use
--stream-frameswhen frame data should be loaded on demand. - Keep browser hardware acceleration enabled.
- Close unused v_ase tabs; inactive tabs pause rendering but retain document state in memory.
- In WSL, keep data in the Linux filesystem.
Installation fails while pip checks an unrelated package version
A package version reported as None usually belongs to a different incomplete
or manually installed distribution in that environment. Run
python -m pip check, repair that distribution, or use a clean environment:
python -m venv .venv
python -m pip install --upgrade pip
python -m pip install v_ase-gui
Run v_ase --help or v_ase gui --help for all CLI options. Report
reproducible problems at
GitHub Issues.
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