I needed to increase the overall size of a three-legged bracket I am making by just a small amount overall, so I thought the easiest way would be to do a minkowski on it.
But when I did, the render time went from 0.545 seconds to over an hour (and still going), then it came up with "Warning: [manifold] Minkowski hard-crashed, falling back to Nef operation."
It's now well over an hour and it's still going- any ideas on what the error means?
I can put the code up if needed, but I don't want to stop it at the moment- I'm hoping it might finish if I leave it a bit longer.

--
Cheers, Ken
bats059@gmail.com
https://vk7krj.com
https://vk7krj.com/running.html

A baby can be defined as an ego with a noise at one end and a smell at the other.
Your job as parents is to teach them to control all three.
My job as a grandad is to tell you how you are doing it all wrong!

scale and minkowski (and positive offset, which is sort of a special
case of minkowski) look like they might do something similar, but they
really don't.

scale() makes every part of the object bigger.  minkowski and offset
make it ... thicker.

Let's look at a simple object:  an O.

text("O");

Let's scale that up by 50%.

scale(1.5) text("O");

Now let's play with offset.  That O starts out about 10 units square, so
scaling it up by 50% added about five units in X and Y.  Let's use
offset to add, say, two units in all directions.

offset(2) text("O");

The new object is about 14 units square, as intended, but it's not at
all the same object.  Where scale made the hole in the middle larger
(just as it made the rest of the figure larger), offset made the hole
smaller, because it pushed the inner boundary inward.

The default operation for offset is equivalent to 2D minkoswki with a
circle.

$fs = 0.5;  // because a default r=2 circle has only 7 sides
$fa = 1;
minkowski() {
    text("O");
    circle(r=2);
}

Again, minkowski pushes the inner boundary inward, because it rolls the
circle around both the inner and outer boundaries.

There is a similar effect for less-than-100% scale and negative offset. 
(And minkowski subtraction, but we don't directly support that.) Scale
makes the object smaller, while negative offset makes it thinner.

So, net, while all three change the size of an object, scale and the
other two produce very different objects.

Sounds like the OpenSCAD built-in resize():

OpenSCAD User Manual/Transformations - Wikibooks, open books for an open world

wikibooks.org

-Revar

On Sep 11, 2024, at 8:58 PM, larry via Discuss <discuss@lists.openscad.org> wrote:

On Wed, 2024-09-11 at 22:05 +0100, Raymond West via Discuss wrote:

If you are 3d printing, as well as scaling it by %, you can put in

the final size you want for each direction.

I bought a Bambu Lab P1S early this year, and have been somewhat
spoiled by a feature in Bambu Studio. If I have an object I want to
scale, it gives me a box (attached image) in which I can choose to
scale by percentage or dimension, and if I uncheck uniform scale, I can
change one, two or three dimensions separately.

I have always had problems with OpenSCAD's scale, in that if I know
what length, width, or height, I want, I needed to do the math (not my
strong suit).

How hard would it be to incorporate something like that in the scale
function (or in BOSL2 for that matter)?

Of course, not everyone would want that functionality, so if it's not
worth the effort, I'm fine with that.

On 11/09/2024 14:56, Jon Bondy via Discuss wrote:

scale() would not help?

All of my OpenSCAD projects use parameters at the top of the

script, height, width, etc. Were I in this situation, I would just

tweak the parameters a bit

Jon

On 9/11/2024 9:45 AM, Ken via Discuss wrote:

I needed to increase the overall size of a three-legged bracket

I am making by just a small amount overall, so I thought the

easiest way would be to do a minkowski on it.

But when I did, the render time went from 0.545 seconds to over

an hour (and still going), then it came up with "Warning:

[manifold] Minkowski hard-crashed, falling back to Nef

operation."

It's now well over an hour and it's still going- any ideas on

what the error means?

I can put the code up if needed, but I don't want to stop it at

the moment- I'm hoping it might finish if I leave it a bit

longer.

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