[OpenSCAD] a matter of speed....

nop head nop.head at gmail.com
Tue Jul 16 08:46:06 EDT 2019


Preview slows down if you have 3D intersections and differences. 3D unions
are fast.

I make a my previews fast making almost everything out of 2D
linear_extrusions and rotate_extrusions unioned together. If I do need a 3D
difference or intersection I factor that bit out and wrap it in render().
That is slow on the first preview but gets rid or any flickering artefacts
and keeps the pan and zoom frame rate high. Also as long as the vertex
count inside the rendered operation is small it doesn't take long.
Typically only a small part of my object gets rendered.

hull() is also fast unless you have an implicit union inside it. I avoid
that by repetition instead of loops and shared translations or rotations.

A complex assembly like this takes 11 seconds to render the first time, 2
seconds for a simple change like moving the door with customiser. It pans
and zooms fluidly and there are no z-fighting artefacts.

[image: image.png]

On Tue, 16 Jul 2019 at 13:19, Doug Moen <doug at moens.org> wrote:

> If preview doesn't work for you because "it often results in objects I
> can't rotate smoothly", then a new GPU should help.
>
> The GPU isn't used for rendering. What does speed up rendering is a large
> CPU cache and fast RAM. For example, see this old forum thread, where
> benchmarks are used to prove this:
> http://forum.openscad.org/OpenSCAD-performance-numbers-td4707.html
>
> Multiple cores helps, but I think this is model dependent, since I don't
> think that multiple cores helps with the final top level union.
>
> Lots of RAM is a good thing, it allows you to render larger models.
>
> Doug Moen
>
> On Mon, Jul 15, 2019, at 7:06 PM, macdarren via Discuss wrote:
> > I have been using scad for some time now...and my computer is getting
> > older...
> >
> > I do many models with threads and other features that just take a long
> time
> > to render.
> > I spend about 25% of my design time trying to either work out speed ups
> to
> > rendering or adding switches to enable high speed vs high detail render
> > options to my designs....
> >
> > Preview is often not really an option...it still takes time and often
> > results in objects I can't smoothly rotate or that have what I might call
> > artifacts that make tight tolerances hard to see.  And since scad has no
> way
> > to actually query objects so I could perhaps use software inspection I
> have
> > to rely on human visual verification.
> > I am okay with that but the rub is it takes too long to fix and re-render
> > things.
> >
> > So thinking about computer replacement...the way to speed these days
> seems
> > to be threading and multiple CPUs and also offloading certain things to
> > GPUs.  So what is the best way to go for a new machine...just get the
> > fastest possible clock rate for the CPU (am maybe forgoing newer cpu in
> > favor or older higher clock rate?..seem I can just ignore core
> > count....since it seems scad is single threaded...or is there a GPU that
> > might help?  Is there any advantages in the various CPU families ... Xeon
> > server class vs i7/i9 CPUs?  How to I select a machine optimized for
> Scad,
> > which is now the only application I find holding me up when working....
> > Is there any option or future thought to multi-thread SCAD?
> >
> >
> >
> >
> >
> > --
> > Sent from: http://forum.openscad.org/
> >
> > _______________________________________________
> > OpenSCAD mailing list
> > Discuss at lists.openscad.org
> > http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org
> >
>
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