Export Geometry in the editor writes STL, 3MF or OBJ by default and five more formats under Advanced. Which one to pick is the easy part. The hard part is that the same model can leave Rig Cad as 500 triangles or 1.2 million depending on four settings, and a slicer treats those two files very differently. This article covers the formats, where the triangles come from, and how to lighten a mesh before it leaves.

The formats and who they are for

Export Geometry lives in the project actions menu of the editor. It lets you choose one object or the whole scene, a file format, and a filename; readers of an embed get the same download when the project allows it.

Table: Export formats offered by the Download model dialog.

Format Best for Carries Notes
STL Most 3D printers and slicers Triangles only No colour, no units; Rig Cad exports in millimetres
3MF Colour and clean data Triangles, node colours, several objects The modern slicer format; keeps the colours you assigned to nodes
OBJ Blender and materials Triangles plus material groups Good hand-off to rendering and sculpting tools
GLTF Web and game engines Triangles, colours, scene Advanced
PLY Vertex colours Triangles with per-vertex colour Advanced; useful for colour-mapped analysis
USDZ iPad and iPhone AR Scene Advanced
DXF 2D cross-section Curves Advanced; a section, not a solid
SVG Vector paths 2D outlines Advanced; laser cutting and drawings

For a print, STL when the slicer is old or the part is one colour, 3MF otherwise. The colours you used as spatial labels while modelling travel into a 3MF, so switch them to the intended palette before exporting, or expect a multi-colour slicer to ask about them.

Where the triangles come from

A mesh-mode primitive is as heavy as its segments. A sphere at 32 segments is 512 triangles; the count grows with the square of the setting. An SDF branch is as heavy as its precision, the sample cell size in millimetres, and the count grows roughly with the surface area divided by the cell size squared.

Table: Measured triangle counts on the companion project and the fillets demo. Times are one machine's solve times, for ratio only.

Geometry Setting Triangles Solve time
Blended part, SDF union precision 0.6 55,548 0.25 s
Blended part, SDF union precision 0.3 209,048 1.07 s
Mesh sphere, radius 15 32 segments 512 1 ms
Extruded plate chamfer edge 220 3 ms
Extruded plate rounded edge 236,128 0.4 s
Gyroid lattice puck, 40 mm precision 0.75 291,974 1.4 s
Gyroid lattice puck, 40 mm precision 0.35 1,228,926 5.7 s

Halving precision quadrupled the blended part's triangles and its solve time. A rounded extrude edge cost a thousand times a chamfer. A lattice at fine precision reached over a million triangles, which is a 60 MB STL. None of that detail is visible on a 0.2 mm layer.

The weight also compounds through the tree. A Boolean of two heavy meshes is heavier than either, and a repeat multiplies its child. Why Is My Model Slow? follows the same numbers from the solve-time side.

What a slicer actually needs

A slicer intersects the mesh with a plane every layer and turns the result into toolpaths. Two properties matter to it, and triangle count is only indirectly one of them.

Watertight. Every edge must belong to exactly two triangles. Boundary edges and non-manifold vertices make a layer polygon that does not close, and the slicer either repairs it by guessing or refuses. Read the topology statistics before exporting: boundary edge count zero, connected components equal to the number of parts you expect. Mesh Cleanup covers Repair, Split Self-Intersections and Collapse Tiny Triangles for when they are not.

Resolution matched to the process. A binary STL costs 50 bytes per triangle, so 200,000 triangles is 10 MB and a million is 50 MB. Slicers cope, but slowly, and the extra facets are invisible once the layer height and the nozzle width have quantised the surface. A chord error around 0.05 mm is already below what a 0.4 mm nozzle can reproduce. For SDF branches that means a precision between 0.2 and 0.5 mm at part scale; for primitives it means segments in the tens, not the hundreds, unless the feature is large and curved.

Units are millimetres and up is +Z. Slicers that expect Y-up handle the swap themselves; do not rotate the model to please them.

Lightening a mesh before export

Work from the source toward the output: fix the setting that made the triangles before you simplify the triangles it made.

Table: Knobs that reduce triangle count, in the order to try them.

Knob Where What it does Cost
segments Mesh primitives and 2D profiles Fewer facets per curve Visible faceting on large curves
precision SDF operations, Pattern 3D Coarser sample cells Detail below the cell size disappears; corners soften
decimation SDF operations Keeps a fraction of surface detail after the SDF is simplified Cheap; the demo exposes it
Decimate step Post-processing stack, mesh solver only Target ratio with a max error and a crease angle that protects sharp edges Mesh only; respects tolerances you set
simplify / tolerance Every Boolean Merges coplanar detail after the operation Default on
pathSimplify 2D SDF profiles Simplifies the sampled contour by a tolerance Measured: 0.5 mm removed 96% of triangles but 1.7% of volume, so check the result

The Decimate step's maxError stops simplification before the surface moves more than that distance, and creaseAngle keeps edges sharper than the angle you set. Together they let you decimate a lattice or a blend hard while leaving a mounting face flat and a bore round. The Post-Processing article has the full ordered stack.

Interactive Sandbox
View project
Drag precision and decimation on the blended part and sphereSegments on the mesh sphere, then read the triangle count and solve time in Object Properties. Export Geometry from the menu to see the file size follow.
Mesh weight and precision demoInteractive Rig Cad editor

Export checklist

  1. Solve is settled and no node is dirty or empty.
  2. Topology: boundary edges zero, components as expected, no self-intersections.
  3. Colours set to the intended palette if exporting 3MF.
  4. Triangle count proportionate to the part: tens of thousands for a hand-sized print, not millions.
  5. The right object selected, or the whole scene if the parts should arrive together.
  6. Filename that records the project and the revision, so the file can be traced back; Versioned Production explains why that matters once you sell the result.

If the exported part needs to fit something, the numbers in Fits, Clearances, and Tolerances apply before you export, not after.