Anvil

A lightweight parametric CAD application for Linux, built for 3D printing.

Anvil is a native parametric solid modeller aimed at people who design parts for their own printer: brackets, enclosures, adapters, jigs, replacement parts. The reference experience is Fusion 360's sketch → extrude → modify workflow, without the cloud, the licensing or the bloat.

It is not a mesh editor, a slicer, or a general-purpose FreeCAD clone.

Status: M0–M5, plus the interface described in CLAUDE.md §10. Constraint-solved sketches drawn in the viewport with inferred constraints, extrude and revolve, fillet, chamfer, shell, patterns and mirror, a persistent topological naming scheme that survives parametric edits, and import/export for 3MF, STEP and STL.

Of the 159 commands the toolbar lists, 63 do something; the rest are greyed with a tooltip saying where they stand. The largest gaps are construction geometry (datum planes, axes, points), the hole feature, and the sketch modify tools — trim, extend and offset. PROGRESS.md lists exactly what is and is not built.

Building

Arch Linux (or CachyOS):

sudo pacman -S --needed cmake ninja gcc git clang doctest \
                        opencascade eigen nlohmann-json minizip-ng pugixml zlib
git clone --recurse-submodules <url> anvil && cd anvil

cmake --preset release
cmake --build --preset release
ctest --preset release

./build/release/bin/anvil

If you cloned without --recurse-submodules:

git submodule update --init --recursive

Presets

Preset	Purpose
debug-asan	Debug with ASan + UBSan. What you develop against.
debug	Debug without sanitizers, for when you need the speed.
relwithdebinfo	Optimised with symbols, for profiling.
release	Optimised. The configuration the performance budgets are measured against.

scripts/ci.sh runs the full gate: formatting check, then debug-asan and release both built with -Werror and both running the test suite.

Usage

  anvil [options] [FILE.anvil]

  FILE.anvil           Open a document on startup.
  --inspect FILE       Dump a document's JSON to stdout and exit.
  --startup-timing     Print milliseconds from launch to the first drawn frame.
  --log-level LEVEL    trace, debug, info, warn, error or off.
  --width / --height   Initial window size.
  --no-vsync           Disable vertical sync.
  --gl-debug           Request a debug context and log driver diagnostics.

--inspect reads one entry straight out of the container without building the document, so it still works on a file this build cannot fully open:

anvil --inspect bracket.anvil | jq .parameters

Modelling

The parametric workflow:

1. Create → Create Sketch (on XY, or on a selected planar face)
2. Draw with L, R, C, A. The tool stays armed for the next shape; Esc puts it down. Constraints are inferred as you go — the glyph at the cursor is what you will get — and typing a number while dragging locks it as a driving dimension. The sketch palette counts the remaining degrees of freedom.
3. Finish Sketch, then Create → Extrude (E)
4. Switch to edge selection (R), click edges, Modify → Fillet (F)
5. Change a parameter — everything downstream rebuilds, and the fillet stays on its edge

Every 3D feature opens a dialog at the right of the viewport with a live preview. Fields take expressions, so wall_thickness * 2 + 0.4 is a valid size; define named parameters in the Parameters panel and reference them from any field. Dragging the arrow in the viewport edits the same value. Enter commits, Esc cancels, and nothing reaches the document until you accept.

Selecting first pre-fills the dialog; running a command with nothing selected opens it waiting for a pick. Shift-click adds to a selection. Resting the cursor over crowded geometry offers a list of what is under it.

Right-click opens a marking menu — flick in a direction and release to fire that wedge without the menu ever drawing. S opens a fuzzy command search where any command can be pinned.

Everything goes through the undo stack — Ctrl+Z and Ctrl+Shift+Z, unlimited.

Shortcut
Ctrl+O / Ctrl+S	Open / Save
Ctrl+Z / Ctrl+Shift+Z	Undo / Redo
Ctrl+Q	Quit
S	Command search
Esc	Back out one level
Del	Delete the selected feature
E / F / Q	Extrude / Fillet / Press Pull
B / G / R	Select bodies / faces / edges
L / R / C / A	In a sketch: line / rectangle / circle / arc
D	In a sketch: dimension

Command keys come from the toolbar layout, so the key a tooltip shows is the key that fires. R is the edge filter outside a sketch and the rectangle tool inside one.

Viewport navigation

Matching Fusion 360's defaults, and rebindable under Preferences → Navigation if you prefer middle-drag to orbit.

Input	Action
Middle drag	Pan
Shift + middle drag	Orbit
Scroll	Zoom toward the cursor
H	Home view
1–6	Front, back, left, right, top, bottom
F6	Fit to the build volume
O	Toggle orthographic / perspective

Layout

core/
  base/       math, Result, logging, ids
  document/   expressions, parameters, features, commands, undo
  sketch/     2D entities, constraints, ISketchSolver
  features/   sketch, extrude, revolve, fillet, chamfer, shell, patterns
  kernel/     the ONLY place OpenCASCADE headers are included
  io/         .anvil container, JSON, STL, 3MF, STEP, PNG
ui/
  app/        window, main loop, session, navigation
  commands/   the command registry and the toolbar layout, which is data
  render/     GL loader, camera, grid, build plate, mesh and picking
  panels/     theme, docked panels, dialogs, sketch view, file dialog
tests/        doctest suites. anvil_core_tests links core alone, which keeps it headless;
              anvil_ui_tests drives panels through real ImGui frames with no window.
docs/         file format and the topological naming scheme.

core/ is testable without a GPU or a window, and OpenCASCADE types never escape core/kernel/ — the core test target compiles without OCCT's include path at all, which is what proves it. Both rules exist so the geometry kernel stays replaceable (CLAUDE.md §4).

The sketch solver sits behind ISketchSolver for the same reason. It is SolveSpace's, vendored under third_party/solvespace — see PROGRESS.md for why, and what that cost.

How a fillet survives a parametric edit

Change an extrude's height and OpenCASCADE renumbers the faces. A fillet storing "edge 7" would silently round a different corner. Anvil names a face after what produced it — an extrude's wall is seeded by the sketch entity that generated it, and sketch ids do not move when numbers do — and names an edge by the two faces meeting along it.

When a reference genuinely cannot be found, the feature errors rather than guessing. docs/topological-naming.md explains the whole scheme.

File format

.anvil is a ZIP with every entry stored uncompressed, so a saved model is greppable and diffable:

document.json    parameters, feature tree
metadata.json    app version, format version, timestamps

grep -a wall_thickness bracket.anvil    # works, by design

Licence

GPL-3.0-or-later. See LICENSE.