MoLaView

Open molecular and crystal structure files directly in a Visual Studio Code editor tab and inspect them in interactive 3D.

Built for local and Remote SSH materials workflows: no Python environment, no external application, no server, and no network access. The extension installs no runtime dependencies - the one bundled third-party component, the GIF encoder, is compiled into the webview script - and the whole package is about 60 KB.

Features

3D structure view with ball-and-stick, sticks, and space-filling representations
Crystal support including unit cells, lattice-axis alignment, and on-the-fly supercell expansion
Trajectories with play, pause, step, scrub, and loop controls, at 1-50 fps
Measurements for distance, angle, and dihedral between picked atoms
Inspectors for composition, lattice details, metadata, element visibility, and bond-detection tolerance
PNG export of the current view, and animated GIF export of a whole trajectory
Perspective and orthographic projection, atom labels, and a light/dark canvas toggle

MoLaView viewing a crystal structure in a VS Code editor tab

Install

Search for MoLaView in the Extensions view (Ctrl+Shift+X), or install from the command line:

code --install-extension ltlinh.molaview

Then open any supported structure file and it renders in the viewer.

Build from source

git clone https://github.com/linhlathuy/molaview
cd molaview/
npm install
npm run build
npx @vscode/vsce package
code --install-extension molaview-1.1.0.vsix

See the install guide for the full walkthrough, including Remote SSH notes.

Test the viewer with the structures and trajectories in test_structures.

Repository Layout

src/        extension host code
webview/    viewer UI and WebGL renderer
playwright/ end-to-end tests
config/     esbuild and Playwright configuration
docs/       install guide, notices

Build and test from the project root:

npm run build      # bundle into dist/
npm run typecheck  # tsc --noEmit
npm run test:e2e   # Playwright end-to-end tests
npm run verify     # all three

Supported Files

CIF, including cell parameters and common symmetry-operation loops
VASP POSCAR, CONTCAR, and .vasp, including suffixed names such as POSCAR_1
VASP XDATCAR trajectories
XYZ and extXYZ, including multiple frames and Lattice metadata
PDB and ENT, including multiple MODEL records and CONECT bonds
V2000 MOL and SDF, including multiple SDF records
ASE ULM .traj

Supported files open in the viewer by default. Use Reopen Editor With... > Text Editor or Molecular Viewer: Reopen as Text to inspect the source.

ASE trajectories expose every frame by default. Frames are read on demand, so a long trajectory opens immediately and only the frames you visit are decoded.

Set molaview.trajectory.maxFrames to a positive number to cap how many frames are loaded; the viewer then spreads that many evenly across the trajectory, always keeping the first and last frame. The playback label shows Frame 250/2500 when every frame is loaded, and Sample 3/11 - Frame 250/2500 when a cap is active. Reopen the file after changing the setting.

Controls

Left drag rotates, right drag pans, and the wheel zooms.
The top toolbar fits the structure, changes projection, aligns along lattice axes, toggles labels, selects distance/angle/dihedral measurement modes, changes the canvas background, saves a PNG, exports an animated GIF, and resets the viewer.
GIF export walks the whole trajectory at the current camera angle and display settings, using the selected playback speed as the frame delay. Progress is shown while it runs and can be cancelled. Exports are limited to 600 frames; use molaview.trajectory.maxFrames to sample a longer run down first.
The Structure inspector shows composition, lattice details, metadata, and supercell controls.
The Display inspector changes representation, sizes, visible geometry, element visibility, and inferred-bond tolerance.
The Selection inspector shows picked atoms and completed measurements.
Multi-frame files display play, pause, step, scrub, speed, frame, and loop controls. Playback runs at 1, 2, 5, 10, 20, 30, or 50 fps.

Offline and Remote Use

All parsers, WebGL rendering code, styles, and icons are bundled in the VSIX. The extension does not make network requests or launch external programs. In Remote SSH sessions, file parsing runs in the remote workspace extension host and the interactive editor is rendered by the local VS Code client.

Current Scope

MoLaView is a read-only atomic-structure viewer. It does not display volumetric density, edit atoms, export modified structure files, parse V3000 MOL records, or read obsolete pickle-based ASE trajectories. CIF support targets the common structural subset and reports unsupported or malformed variants instead of guessing coordinates.

VESTA Reference Boundary

VESTA informed the workflow and terminology only. This extension does not contain, modify, call, or redistribute VESTA code, binaries, configuration, or artwork. VESTA remains a separate copyrighted application by Koichi Momma and Fujio Izumi.