[OpenSCAD] multmatrix expands the input matrix to 4x4?

nop head nop.head at gmail.com
Wed Jul 3 18:00:46 EDT 2019


Passing 3x3 makes sense if you only want to rotate, so some people might do
that. Similarly 2x2 for rotate around z. And the first three elements on
the last row are ignored anyway, so passing 3x4 also makes sense.

On Wed, 3 Jul 2019 at 22:47, adrianv <avm4 at cornell.edu> wrote:

> I think the argument for tightening size requirements would be that
> mathematically the size needs to be 4x4 and if it isn't it *could* be
> intentional, or it could be programmer error, and by issuing a warning, you
> may help the programmer avoid bugs.
>
> The argument for the current behavior is that the programmer has the
> convenience of specifying only what is needed, which may simplify the code
> and make it more readable and maintainable.
>
>
> nophead wrote
> > I think it should warn if you don't pass a vector of vectors, but other
> > than that, what is the point in tightening up the size requirements?
> >
> > On Wed, 3 Jul 2019 at 22:24, adrianv <
>
> > avm4@
>
> > > wrote:
> >
> >> This sounds like pretty intentional behavior.  Is there a prevailing (or
> >> at
> >> least common) belief that it's wrong and needs to change?
> >>
> >>
> >> nophead wrote
> >> > The code
> >> > <
> >>
> https://github.com/openscad/openscad/blob/69bf5a55475102be43c2ddc698198e85821332b3/src/transform.cc#L204&gt
> >> ;
> >> > creates
> >> > a 4x4 identity matrix and then for each element it looks to see if the
> >> > corresponding element exists in the passed matrix and if it does it
> >> > overwrites that entry.
> >> >
> >> > So basically it tries as hard as it can to convert any shape matrix to
> >> > fit.
> >> > Any element it can't find is left as the value from the identity. If
> >> the
> >> > argument isn't even a matrix it silently uses the identity.
> >>
> >>
> >>
> >>
> >>
> >> --
> >> Sent from: http://forum.openscad.org/
> >>
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> >>
> >
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>
>
>
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>
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