[OpenSCAD] STL without render?

Rob Ward rl.ward at bigpond.com
Wed Jun 1 08:29:19 EDT 2016

I like the idea of modeling cellular activity or constructions. OpenSCAD 
lends itself really well to visualizing these things, but 
computationally we are still limited compared to the biological 
capacity. I think a previous thread discussing narrowing bifurcating 
cylinders with smooth transitions, similar to what we could expect going 
from arteries to capillaries and back to veins, was running into a 
similar exponential growth in the computational challenge. It reminded 
me though that as every cell reproduces, it essentially spawns another 
two computational units in the nucleus of those new cells (The answer to 
the N squared problem?).  The programs in the DNA are applying their 
rules in the new environment for each new cell.  I can't see us 
surpassing this system too quickly with our silicon models, but I admire 
the efforts of people such as Ben who are investigating these areas.

On 01/06/16 21:30, Ben Suter wrote:
> 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
> hoped).
> 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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