# [OpenSCAD] Difference between modelling with Openscad and Freecad

nop head nop.head at gmail.com
Thu Oct 3 08:04:18 EDT 2019

```I round most of my corners and it only needs trig, not calculus, because I
only round with tangential circles. I don't see a need for higher order
curvature continuity.

I do use an iterative solver for positioning pulleys and belts because
there isn't algebraic solution, surprisingly.

On Thu, 3 Oct 2019 at 12:56, adrianv <avm4 at cornell.edu> wrote:

> In my experience, the answer to your question is that you want to do some
> kind of rounding or edge treatment that finishes before the heat death of
> the universe---or maybe just part of the model needs to be rounded.  So
> minkowski() is out. I made a model based on a sine wave shape.  The model
> wasn't designed around some spec that required certain dimensions for
> everything, so some things were arbitrary, but I still wanted to round off
> those arbitrary ends.  I'm not saying it can't be done, but you're going to
> need calculus and you might potentially need to solve a transcendental
> equation, which means you need to implement an iterative solver (e.g
> Newton's method using tail recursion) unless you want to just hard code
> values.
>
> Just knowing the location of the intersection may not be enough to solve
> problems like this in general.  At least in principle, when I 3d print
> something every edge should be rounded unless a specific functional reason
> requires a sharp edge.  It would be nice if doing this wasn't so
> difficult.
>
>
> nophead wrote
> > I just don't come across that in practice. If an object has an important
> > dimension, that is usually input parameter of the object, so even if it
> is
> > created with an intersection, or a difference, the part that does the
> > removal has to be positioned so that it gives the required important
> > dimension. That may need some trig but it is never more than I learned at
> > high school 40 years ago and can still remember, so I wouldn't call it
> > complex. Just a bit of triq and some circle intersection equations that I
> > Google for.
> >
> > Why would you do some arbitrary intersection and then try to find the
> > resulting dimensions?
>
>
>
>
>
> --
> Sent from: http://forum.openscad.org/
>
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