GDS Lens

GPU-accelerated GDSII and OASIS viewer for VS Code, built in C++ and compiled to WebAssembly. It renders layouts of over 100 million polygons with nothing else installed, including on vscode.dev.

Try it in the browser by dropping a layout on the page. The extension is the same viewer inside VS Code.

Install

Search for GDS Lens in the Extensions view, or install it from the Marketplace or Open VSX. Then open any .gds, .oas, or .oasis file. Gzipped files open too. The format is read from the file's contents, not its extension.

Drag to pan. Scroll to zoom.

Features

• Large layouts: GPU instancing draws repeated cells once. Up to 820M polygons once flattened, a 37 MB file on screen in 0.25 s, and smooth panning and zooming on a 127M polygon layout.
• Ports: photonic and electrical ports stored in the layout's metadata are drawn with orientation arrows, colored by type, and listed for the top cell.
• Layer panel: automatic colors, per-layer toggles, filter, solo, shape counts, bulk show/hide. Load a .lyp layer properties file to match your PDK colors.
• Inspect: click a shape to see its layer, cell path, bounding box, area and perimeter.
• Hierarchy: browse the cell tree, frame any cell, outline every placement of it, or show any cell as the new top.
• Live preview: a Python layout script's show() call opens or reloads the layout in VS Code.
• Find: search cells and text labels by name.
• Ruler: measure with snapping to vertices and edges.
• Saved views: name a camera position and layer set and return to it later.
• DRC/LVS markers: browse .lyrdb or ASCII marker databases as an overlay.
• Compare layouts: open two files overlaid in one viewer, crossfade between them, and highlight where they differ.
• Auto reload: when a generator script rewrites the file, the view updates and keeps your camera and layer visibility.
• Theme: follows your VS Code light or dark theme.

Use the viewer

Inspect a shape

In Pan mode, click a shape to select it. Of the shapes under the pointer, the one whose outline is nearest is chosen, so clicking inside a small shape picks it rather than a large box around it, and clicking on the large box's edge picks the box. The selected shape is outlined on the canvas and a card shows its layer, the cell it belongs to and that cell's path from the top (including which copy of an array you clicked), its bounding box, width and height, area, perimeter and vertex count. Click the same spot again to step to the shape underneath. Hidden layers are skipped. The card's buttons show the cell as the new top, frame the shape, or copy the details as text. Click empty space or press Esc to clear the selection.

The first click in a layout reads the file's hierarchy once, which takes about as long as opening it; clicks after that are immediate.

Hierarchy

Press H or click Hierarchy to open the cell tree. Click a row to frame that cell and outline every placement of it on the canvas. Press Esc to clear the outlines. A cell placed more than once by its parent is one row marked ×N.

To look at one cell on its own, click ⤒ on its row (Show as new top). The view then shows only that cell and what it places, at the cell's own origin, and the layer counts, search, ports and hierarchy follow it. Back to all above the tree, or Esc, returns to the full layout. A file with several top cells lists each as a root row, so this is also how to view one of them alone. Each switch re-reads the layout, so on a very large file it takes about as long as opening it.

Find

Press / to open the search box. Cells matches cell names and opens the tree down to the result. Labels matches the layout's TEXT labels, including labels on hidden layers, and pans to the match. Use ↑ ↓ and Enter to pick a result. The tree returns when you clear the box.

Layers

Every layer gets a color and a row with a toggle and its shape count in this file, with no setup. Filter by layer number, datatype, name, or group. Show: All | None | Invert applies to the filtered rows. Click S to solo a layer; click it again to restore the previous selection. To use your PDK's colors and groups, click Load .lyp File in Display. The .lyp is remembered per layout.

Display

Infill, Text, Ports, Merge Overlaps and Grid are remembered: the next layout you open starts with them set the way you left them.

Saved views

Click Save Current View to store the camera and layer visibility under a name. Click a saved view to restore both. Views are kept per layout and survive closing the file.

Measure

Press M to switch to Measure mode. Click two points to read the distance, Δx, Δy, and angle. Points snap to the nearest vertex or edge. Hold Alt to place a point freely, or Shift to constrain to horizontal or vertical. Finished rulers stay on the canvas until you clear them with Esc.

Coordinates

The pointer coordinate is shown below the scale bar in microns. To copy it, right-click the layout and choose Copy coordinate. To jump to a coordinate, run GDS Lens: Go to Coordinate and paste it. Units nm, um, µm, and mm are accepted, as are the formats DRC reports use, such as (x, y) or x=…, y=…. A crosshair marks where you landed.

DRC/LVS markers

Click Load Marker File and choose a .lyrdb report database or an ASCII DRC results file. Violations draw as a red overlay above all layers. The Markers panel lists each rulecheck with a visibility toggle. Click an item to zoom to it, or press [ and ] to step through. The marker file is remembered per layout.

Ports

Each port is drawn as a bar across its width with an arrow in the direction it faces: orange for optical, green for electrical, blue for other types. The Ports folder lists the top cell's ports; click one to center on it. The overlay is off until you turn on Display > Ports. The top cell's ports are drawn at every zoom, and ports inside placed cells are drawn once you zoom in far enough that 3,000 or fewer are in view. Ports are read from the port metadata that Python layout tools store in GDSII and OASIS files. Files without it look unchanged.

Reload

When the open file changes on disk, a header offers Reload. Reloading keeps the camera and layer visibility. Click Always to reload without asking.

Compare layouts

Two ways in:

• With a layout open, use the compare button in the editor's title bar, or run GDS Lens: Compare Current Layout With..., and pick the file to compare against. The open layout is A, the one you pick is B. The picker opens in the open layout's folder.
• Or select two layout files in the Explorer, right-click, and choose Compare Layouts. Running that command with nothing selected asks for both files.

Both open in one viewer, overlaid through one camera, and the panel gains a Compare folder:

• A ↔ B crossfades between them. Either end shows one layout on its own, the middle overlays both. Flicking between the ends shows what moved.
• Tint sources, off by default, shifts each layout toward its own hue, so two revisions with the same colors can be told apart in the overlay.
• Highlight differences marks, layer by layer, where the two disagree: red where only A has geometry, green where only B does. It works at the resolution you are viewing, so zoom in to resolve smaller differences. It shows where to look; it is not a geometric XOR and does not report an area.

The layer list shows both layouts' layers, marked A or B where only one of them has it, so a layer added or removed between revisions shows up as a row. The hierarchy browser roots both cell trees, and cell and label search covers both, with the same marks on the results.

Everything else is single: one camera, one set of rulers, one .lyp, one marker database. The reload banner names whichever file changed on disk, and reloading clears rulers, as it does for a single layout.

Live preview from Python

In desktop VS Code, GDS Lens listens for the layouts that Python layout libraries send with c.show(). Run a script that calls c.show() and the layout opens in GDS Lens beside the editor you are working in. If that layout is already open, GDS Lens reloads it and keeps the camera and layer visibility; c.show(keep_position=False) frames the whole design instead. A lyrdb passed to show() loads as the layout's marker database. Your Python code does not change.

show() sends the layout to port 8082 on your own machine. Only one program can listen on that port at a time, and other layout viewers use it for the same purpose. If another program has the port when VS Code starts, it keeps it and show() goes there; the status bar shows the port with a disconnected icon, and clicking it tries again. If GDS Lens has the port, the other program cannot listen on it until you close VS Code or turn the server off. With several VS Code windows open, the window you switch to takes the port when no other program holds it.

To turn the server off, set GDS-Lens.liveServer.enabled to false. The server is not available on vscode.dev or github.dev, because a browser cannot open a network port. GDS Lens ignores the libraries, l2n, technology and markers that show() can send; they are named in the log show() prints.

Performance

Parsing, flattening, and triangulation run in a WebAssembly worker, off the main thread, so the editor stays responsive while a file loads. Drawing is WebGL2 on the GPU, with one vertex buffer per layer.

A cell is GPU-instanced based on what instancing saves, not on how often it is placed. Instancing avoids storing a flattened copy of every placement, but costs a draw call per cell per layer in every frame. A cell is instanced when its flattened copies would take a lot of memory, so a cell placed 100,000 times still instances, while a small cell placed a dozen times is flattened into its layer's buffer.

Panning and zooming a very large layout reprojects the last render instead of redrawing the geometry, then does one real render when the camera stops. The frame it settles on is the same as one drawn without reprojection. Merge Overlaps and the compare difference highlight are not covered and redraw every frame.

Measured on generated stress layouts and a 37 MB test layout:

• The 37 MB GDSII file is on screen in about 0.25 s.
• Dragging a 127M polygon layout takes 8.4 ms a frame, down from 606 ms.
• A test chip of 2.5M polygons in 8,000 distinct cells draws a frame in under 1 ms, down from 108 ms, and loads in 1.27 s, down from 4.35 s.

Everything is held in the 4 GB address space of 32-bit wasm, which sets these limits on what loads. The limit depends on how much of the layout is distinct geometry:

To measure your own files, run npm run bench -- <file>.... See Benchmarking.

Keyboard shortcuts

H, /, M, [, ], Ctrl+G and Ctrl+K D are VS Code keybindings, so you can change them in Keyboard Shortcuts: search for GDS Lens. The single-key ones apply only while the viewer has focus and you are not typing in one of its text boxes. Ctrl+K D applies to a single layout, not to Compare.

To see the list in the viewer, run GDS Lens: Show Keyboard Shortcuts or use Display > Keyboard Shortcuts in the viewer's panel. The list shows the default keys, and its Customize... button opens Keyboard Shortcuts filtered to GDS Lens.

Commands

Settings

Release notes

See CHANGELOG.md. Build instructions are in DEVELOPING.md.