3DFastCraft

A lightweight Windows app for 3D printing: shapes at exact sizes, cut and combine, a library of parts made to your numbers, watertight STL and 3MF.

Website: 3dfastcraft.com · Download the latest release

In active testing. Tools marked beta are new and still being proved in real prints - check what they give you before a long print. Releases come often.

The idea

It began as a replacement for Microsoft 3D Builder, which Microsoft retired: the same short path from a shape on the plate to a printable part, with almost nothing to learn first. It then grew well past it - a parts library, working mechanisms, molds, patterns, lithophanes.

The Classic view shows the tools 3D Builder had, for anyone who wants the old app back. Advanced (the default) has every tool. Only buttons are hidden - every key works at both levels. The Custom tab at the end of the ribbon holds the buttons you use most: right-click any button, even a greyed one, and choose Add to Custom tab; right-click one there to move or remove it.

Almost all of it is written by Claude Code from prompts.

Features

Insert

• Shapes - cube, cylinder, cone, sphere, pyramid, wedge, torus, hexagon, tetrahedron, landing on the plate at a sensible size.
• Custom shape - a primitive with its segments and roundness chosen before it is made.
• Text - lettering as an object: flat, round a circle or round a cylinder, any installed font.
• Sketch - lines, arcs, curves, freehand or an SVG on the plate, extruded or revolved. The pointer's X and Y are read off the axes, and the line, rectangle or circle being drawn - or the sides of a corner being dragged - carries its length. Right-click finishes the line; Esc drops what is half drawn, then leaves the sketch and puts the camera back.
• Import - STL, OBJ, 3MF, SVG as a solid; another project joins the plate.
• Library (Ctrl+L) - parts made to your numbers, previewed as you type, remade later with Edit settings: boxes and Gridfinity, organizers, hinges, clips, threads, washers, knobs, gears and mechanisms, stairs, windows, doors, roofs with dormers, lithophanes and lamps, calibration prints.
  • Working model - any mechanism as a set to print and turn by hand: base, D-shafts, crank or handwheel, guides that print without supports. Turn it plays the motion first and stops at a jam.
  • A set of parts is an assembly - laid out for printing or put down together, it goes in as an assembly: picked, moved and copied by its name, each part still its own object. Windows, doors and dormers come with their glass as a part of its own, and the glass can be one clear sheet across the back, as thick as the frame is deep. Doors can be arched; stairs can have a porch; roofs can make their dormers separate parts, each standing in a hole cut to its footprint. While the panel is open the whole set is held, with Move, Rotate and Scale on it.
  • Resizing the preview on the plate - the size boxes or the handles - changes the part's own size settings and remakes it rather than stretching it: a roof made longer keeps its tiles.
• Lithophane - a photo as a plate lit from behind; flat, curved, or a lamp of 3-12 sides on an E26/E27 socket base.

Edit

• Undo, copy, paste - paste lands where the copy came from, also between two app windows.
• Duplicate - beside, or in place.
• Subtract / Intersect / Merge (Ctrl+- / Ctrl+=) - with Subtract, the cutter is the last one picked; a tolerance takes it out that much wider, so printed parts fit.
• Split - with a plane you drag or type; keep either half or both.
• Set pivot - turn and measure about a point you click (a shaft hole, a hinge line).
• Round edges, Twist / Taper / Bend, Simplify, Smooth, Hollow.
• Fill up - fills what the part would hold if liquid were poured in from above, to a level: the inside of a cup or a box, a recess, a sealed hollow; a pocket open to the side fills only up to its opening, and with The plate is a floor a tube or walls standing on the plate fill too. Solid, or as a part of its own that fits the inside exactly (a second filament, or a cavity's volume).
• Color and filament - per object; 3MF carries both.

Align

• Drop to plate - sets the selection on Z = 0.
• Drop down (End) - moves the selection straight down until it rests on whatever is under it, or on the plate. It goes by the shapes, not their boxes, so crossed ridges stop where they meet. With Ctrl or Shift (or Ctrl+End) it sinks 0.2 mm into the part below, so Merge joins them as one solid instead of two touching faces.
• Place on face / Best face down - tip a part onto a face you click, or pick from every way up ranked for printing.
• Align to face - click a face on any object; then for X, Y and Z choose a place on that face (near edge, middle, far edge) and the point of the selection that goes there. Near to near sits it flush; near to far stands it beside. Red marks the place, blue the point.
• Center face to face - click a face on the selection, then one on another object: their middles meet on the axes you tick. Click the side of a pin or the wall of a hole and the round surface is taken whole, by its axis - Apply puts the pin on the hole's axis (turning it parallel first, if asked) and the panel reads both diameters and the gap.
• Align, Distribute, Fit, Mirror - line up on X, Y or Z, spread evenly, fit to the plate. Distribute can also lay each part on its best face and drop it to the plate, to arrange a print in one go.

Tools

• Mold - a silicone mold that comes apart: split at the widest section, keyed, with pour hole and vents.
• Repair / Rebuild - mend an open mesh, or remake the surface from scratch.
• Convex hull - wrap parts in one skin (two cylinders into a slot).
• Voronoi - cut a part into a web of struts; watertight by construction.
• Extrude down - a flat base under a scan, a relief or a tilted part.
• Split with connectors - halves that go back together one way: pins, pegs or brick studs.
• Connect objects - pins or pegs through the face two resting parts share.
• Hole - plain, countersunk or counterbored, nut pocket, heat-set insert; one, a row or a bolt circle. With several parts selected it drills them all, lined up; All the way through goes through the whole stack.
• Keyhole - slots to hang a part on a wall, with printed studs and a drilling template.
• Emboss - lettering, an SVG or a picture (PNG, JPEG) raised or cut into a face, flat or wrapped, or a texture over it. On the face: the circle moves it freely, the arrows across or up only, the knob turns it (15 degree steps; Alt turns freely, or type Turn), and the corner squares resize it along the surface - a texture's corners resize the area it covers, so a corner brick can meet the corner of the face. Raised work keeps off windows and doorways already cut in the face. Keep as its own part prints it in a second filament.
  • Rubble, Coursed stone, Bark and Grain are 3D textures: stones of every size in mortar, uneven courses of squared stone, fissured plates, flowing wood grain with knots. Round a barrel they go the whole way round as one closed ring, no seam; Perimeter takes the walls of a box, a house or any upright part with flat sides as one strip that goes round the corners.
• Cladding - walls built the way a mason builds them, round a house or any upright part: bricks in a bond with corner bricks, logs, siding, rubble or coursed stone with cornerstones. Texture and Cladding show each pattern flat and in 3D - for log walls, a corner of the wall. Siding, rubble, coursed stone and bark can have no groove at all.
• Engrave - brick, tile, plank, grain and more, cut or raised, laid around openings.
• Repeat - along a line, round a circle (with a rise, for spiral stairs) or in a grid.
• Measure, Fit check, Surface info - distances, overlap or gap between parts, and a face's middle, direction, size and area.

File

• Settings - printer profiles, one per printer and filament: nozzle, layer, and the fits the tools start from - sliding clearance (lids, hinges), hole clearance (Hole), press fit (the pins of Split and Connect), brick fit and thread clearance. Printer profile test in the Library prints every fit at once, a few samples either side of the profile's number or up from nought.
• Projects are .3mf files: the plate as any slicer and Explorer see it, with the editable project and its versions inside (Ctrl+Alt+S saves one, with a small picture of the plate); restore is an undo step. A .3dfc from before 4.3 is imported, without its versions.
• Export STL (binary or ASCII) or OBJ - everything or just the selection; reports triangles, volume and whether it is watertight before writing. For 3MF, save the project.
• Blueprint (Ctrl+P) - front, top, side and isometric views with dimensions and a title block; print, PDF or PNG, plus a parts list.
• Export session / Record - every undo step as a file, or a screenshot after every action.

View

• Axis views, Wireframe, X-ray (X), Outline, Overhangs (faces that will need support), Grid.
• Units - mm, cm, m, in or ft; every box and tool panel reads in them. Models are always stored and exported in millimeters.
• Model scale - set 1:87 and a second set of boxes reads real size beside the model's.

Working with it

• Selection - Sticky (default, as 3D Builder): a click toggles one object. Off: Explorer rules - Ctrl+click adds, Shift+click takes a range, clicking empty space clears. A click on a part of an assembly picks the whole assembly; Alt+click picks the one part. The objects list can be dragged taller by its bottom edge.
• Handles - M move, R rotate, S resize; Snap to 1 or 5 mm. O resizes one way only, the opposite face staying put. The resize strip reads mm or %; the box corners, dragged, resize in proportion. With several parts selected they move, turn and resize as one object; the Each button gives every part its own centre and axes instead.
• Stop on contact (C) - a dragged part stops where its shape meets another, not its box. Parts that already overlap move freely.
• Number boxes - every one, in every panel - take +=5, -=5, *=1.5, /=2; the wheel and arrows nudge (Shift ×10, Ctrl ×0.1), and a count stays whole. Enter applies, Esc takes back what was typed, and a box left holding something that is not a number goes back.
• A tool in hand has the plate to itself - only the selection is drawn until it is put down; X-ray shows the rest. Tools that pick a face on anything (align to face, center face to face, surface info, measure) keep everything.
• Enter applies the tool in hand, Esc puts it down, Ctrl+Space runs the last tool again. H / L hide or lock the selection. F1 lists every key.

Formats

Format
.stl	Binary (default) or ASCII. One triangle soup - no separate parts.
.obj	Named, separate objects, colors in a .mtl sidecar.
.3mf	The project: parts, names, colors, units and filaments with a thumbnail, as any slicer reads them, and the editable project with its versions in 3DFastCraft/project.json. Any 3MF imports.
.3dfc	The project before 4.3. Import only: its parts come in as they were, its versions do not.

Requirements

• Windows 10/11, 64-bit.
• Direct3D 11 graphics (feature level 11_0) - any integrated GPU since about 2010. Without it the app says so and stops: a VM without a display driver, some remote desktops, or a fresh Windows still on the Basic Display Adapter.

Building

build.bat

A self-contained build\3DFastCraft.exe (~190 MB), no .NET needed. run.bat starts it, or runs from source if nothing is built. From a shell:

dotnet run --project src/FastCraft3D

dotnet test

Needs the .NET 8 SDK. PublishTrimmed is deliberately off: WPF resolves XAML types by reflection, and trimming breaks the app at runtime.

How it works

• Layers. FastCraft3D.Geometry and the app's Model/ and Io/ know nothing of the renderer; only Render/ touches Direct3D (HelixToolkit.SharpDX). Generators live in their own project and reach the app only through a small contract.
• Booleans go to Manifold first and fall back to a BSP engine (Csg/) when it will not load or a solid is not closed. The BSP runs in double precision on a 256 MB-stack thread, in parallel above 512 polygons with output identical to the serial path. Its results are repaired and T-junctions stitched, or a closed surface reads as broken.
• Watertight or refused. Anything built on a boolean checks the result and refuses rather than ship a broken model. Aggressive healing was tried and made things worse.
• Split by a plane does not use the boolean: PlaneClip cuts the triangles and fills the opening - 214k triangles in 1/25 s, where the boolean took 20 s and tore.
• Lettering is laid out flat; an IPlacementSurface says where a flat point lands - a face, a barrel, a ball - and only steps that stray from the surface are split.
• Handles are 2D, drawn on a canvas by projecting the selection's box, so they stay clickable at any zoom and are testable without a GPU (IScreenProjector).
• Z is up in two places that must agree: the camera and the viewport's ModelUpDirection.
• The object list does not bind ListBoxItem.IsSelected: fresh containers would push false back and undo selections made in code. SelectionListSync mirrors it by hand.
• Mirroring flips winding once, in MeshTransform.Transformed, or exports come out inside out.

Known limits

• Booleans on imports above ~200k triangles can be slow; Abort stops one and leaves the model as it was.
• Patterns and wrapped lettering with counters (O, B, A) can be refused on a face already cut about or on a barrel - refused, never left torn. Raised instead of cut avoids the boolean.
• A face with a round hole cannot take a pattern; pattern before merging a boss onto it.
• A set put down assembled is an assembly, not one solid - lay it out to print it.
• A fine groove on a 3D texture means a fine mesh: a few hundred thousand triangles on a big wall, a minute or two to apply. A coarser pitch or groove is much quicker.
• Undo keeps about a gigabyte of history; the oldest steps go beyond that, with an offer to save a version.
• SharpDX 4.2 is unmaintained upstream - the renderer-agnostic core is the insurance.

Layout

src/FastCraft3D.Geometry/     meshes, primitives, transforms, repair, CSG, plane split, gears,
                              threads, Engraving/, Sketches/, Drawings/, Moulding/
src/FastCraft3D.Generators/   the Library: contract, generators, their panel, motion
src/FastCraft3D/
  Model/      scene, objects, bed placement, Commands/ (undo)
  Io/         STL, OBJ, 3MF (projects too), SVG, pictures, recovery, settings
  Render/     the only Direct3D layer, and the on-screen handles
  View/       tool panels, dialogs, keys, object list
  ViewModels/ commands and state
tests/FastCraft3D.Tests/      geometry, CSG, IO, generators, tool flows, handles
tools/                        checking exports by measurement; tools/ui drives the running app

Licence

BSD 3-Clause with the Commons Clause - use, change and pass it on freely, in a business too; selling the software itself needs a commercial licence, so ask. Models you make are your own. See LICENSE and THIRD-PARTY-NOTICES.md.

Contributing

Bug reports, models that break something, and patches are welcome - see CONTRIBUTING.md.