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The limits of model complexity

J
jon
Wed, Mar 1, 2023 12:07 AM

I am doing an "art" project for a friend, and the result contains
approximately 10,000 spheres using the default $fn.  I can compute this
with F5 in about 2 minutes.  When I try F6, after an hour or so,
OpenSCAD crashes when it reaches the limit of 32 GB of memory use.

What is the limitation on the size of a 3D model in OpenSCAD (counted in
triangles, I guess)?  Any idea what else might cause me to use 32 GB of RAM?

Jon

I am doing an "art" project for a friend, and the result contains approximately 10,000 spheres using the default $fn.  I can compute this with F5 in about 2 minutes.  When I try F6, after an hour or so, OpenSCAD crashes when it reaches the limit of 32 GB of memory use. What is the limitation on the size of a 3D model in OpenSCAD (counted in triangles, I guess)?  Any idea what else might cause me to use 32 GB of RAM? Jon
AM
Adrian Mariano
Wed, Mar 1, 2023 12:15 AM

Do you need an output STL with only one object in it?  If not, use a dev
version and enable lazy union and you might be able to make this work.  I
assume that the problem you're facing has to do with trying to compute the
unions of the facets on 10k spheres, which could mean conservatively a
billion tests for facet intersection.

On Tue, Feb 28, 2023 at 7:08 PM jon jon@jonbondy.com wrote:

I am doing an "art" project for a friend, and the result contains
approximately 10,000 spheres using the default $fn.  I can compute this
with F5 in about 2 minutes.  When I try F6, after an hour or so,
OpenSCAD crashes when it reaches the limit of 32 GB of memory use.

What is the limitation on the size of a 3D model in OpenSCAD (counted in
triangles, I guess)?  Any idea what else might cause me to use 32 GB of
RAM?

Jon


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Do you need an output STL with only one object in it? If not, use a dev version and enable lazy union and you might be able to make this work. I assume that the problem you're facing has to do with trying to compute the unions of the facets on 10k spheres, which could mean conservatively a billion tests for facet intersection. On Tue, Feb 28, 2023 at 7:08 PM jon <jon@jonbondy.com> wrote: > I am doing an "art" project for a friend, and the result contains > approximately 10,000 spheres using the default $fn. I can compute this > with F5 in about 2 minutes. When I try F6, after an hour or so, > OpenSCAD crashes when it reaches the limit of 32 GB of memory use. > > What is the limitation on the size of a 3D model in OpenSCAD (counted in > triangles, I guess)? Any idea what else might cause me to use 32 GB of > RAM? > > Jon > _______________________________________________ > OpenSCAD mailing list > To unsubscribe send an email to discuss-leave@lists.openscad.org >
JB
Jordan Brown
Wed, Mar 1, 2023 1:21 AM

On 2/28/2023 4:07 PM, jon wrote:

I am doing an "art" project for a friend, and the result contains
approximately 10,000 spheres using the default $fn.

The number of faces, and thus the complexity of the model, is by default
dependent on the size of the spheres.

The default $fn is zero, which means to calculate it from $fs and $fa.

The default for $fs is 2, and the default for $fa is 12.

A circle will by default have at least 5 sides, and no more than 30,
depending on its size.  A circle with radius less than about 1.6 will
have 5 sides.
A circle with radius larger than about 9.6 will have 30 sides.

I believe that spheres follow the same rule, with respect to the number
of sides around their equator.  The square of the number of sides gives
a somewhat high approximation of the number of faces.

Default spheres range from 20 facets to 814 facets.

On 2/28/2023 4:07 PM, jon wrote: > I am doing an "art" project for a friend, and the result contains > approximately 10,000 spheres using the default $fn. The number of faces, and thus the complexity of the model, is by default dependent on the size of the spheres. The default $fn is zero, which means to calculate it from $fs and $fa. The default for $fs is 2, and the default for $fa is 12. A circle will by default have at least 5 sides, and no more than 30, depending on its size.  A circle with radius less than about 1.6 will have 5 sides. A circle with radius larger than about 9.6 will have 30 sides. I believe that spheres follow the same rule, with respect to the number of sides around their equator.  The square of the number of sides gives a somewhat high approximation of the number of faces. Default spheres range from 20 facets to 814 facets.