[OpenSCAD] STL without render?

Ben Suter ben.suter at gmail.com
Wed Jun 1 07:30:39 EDT 2016

Is it possible to save an STL file without going through the full render step?

It frustrates me that I can *see* the surface model using "preview",
but apparently can not simply save this as an STL file?

Background: I am using OpenSCAD to generate surface models of neurons,
because the ability to programmatically define 3D surfaces from a set
of tapered cylinders closely matches the way in which neuronal
geometry is represented when derived from experimental measurements.
My goal is to make an STL file that I can use for 3D printing - I
don't care about lighting, viewpoints, textures, colors. Just the pure
surface model.

Currently the render takes 2.5 hours per neuron, severely limiting my
ability to process many neurons and making me doubt whether it's
feasible for me to assemble a single scene with ~50 neurons (as I had

In any case, I'm very happy to have found OpenSCAD and have to say
it's been a great pleasure using it in my processing pipeline. Thank
you, and please keep up the great work!

PS: Currently my scene consists of a few thousand individual cylinders
and spheres, each with its own translation and rotation relative to
the origin. However, each of these segments naturally falls into a
geometrical hierarchy - so alternatively I could represent the scene
as a hierarchy of rotations and translations of each child segment
relative to its parent. Is there reason to believe that the
hierarchical representation (with few root nodes) would render faster?

PPS: Here's the console output after my latest render - note this is
on a 16-core Xeon / Windows 7 64-bit / 72 GB RAM / SSD / GTX 970
machine. Are there any OpenSCAD settings I should modify to make
better use of these resources?

Geometries in cache: 6514
Geometry cache size in bytes: 60051248
CGAL Polyhedrons in cache: 0
CGAL cache size in bytes: 0
Total rendering time: 2 hours, 19 minutes, 58 seconds
Top level object is a 3D object:
Simple: yes
Vertices: 490328
Halfedges: 1703918
Edges: 851959
Halffacets: 730078
Facets: 365039
Volumes: 3
Rendering finished.

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