Re: Discuss Digest, Vol 58, Issue 8

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Re: Discuss Digest, Vol 58, Issue 8

jim_klessig
Robin wrote




I agree completely. I had just been hoping that there was a simpler Openscad
solution that I was not aware of - especially as it seems so much an
integral capability of Freecad and SolveSpace
_____________

From my point of view, it comes down to the fundamental difference in the conceptual way Fc and openscad work. 

In FC, you have an object from which you can "grab" a face, a line, or a point, and do something to it, or in a specific relationship to it.

In Openscad, there really is nothing to "grab". None of the geometry exists until you "F6" it. 

cant speak to Solvespace.

In your original case of placing a feature perpendicular to the face of an extruded polygon, one way is to work it backwards. 

Orient your polygon  so that it is on the xy plane, and your segment (soon to be face) is on the x axis, and then extrude in the z axis for your extrusion and then make your other object extend out in the "y" direction.  Then manipulate the new combined object as needed to get the face where you want it.
I guess it would be relatively simple to make a module that took an n sided polygon and allowed you to place one of "n" objects perpendicular  to a face. you would still need to know where you want them in z and y, which could be more vector inputs to the module.
just my probably clueless 2c worth.


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-------- Original message --------
Date: 9/9/19 9:00 AM (GMT-08:00)
Subject: Discuss Digest, Vol 58, Issue 8

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Today's Topics:

   1. Re: How to make a cylinder perpendicular to a sloping face
      (Jordan Brown)
   2. Re: How to make a cylinder perpendicular to a sloping face
      (adrianv)
   3. Re: How to make a cylinder perpendicular to a sloping face
      (Robin2)


----------------------------------------------------------------------

Message: 1
Date: Sun, 8 Sep 2019 23:47:54 +0000
From: Jordan Brown <[hidden email]>
To: OpenSCAD general discussion <[hidden email]>, nop head
<[hidden email]>
Subject: Re: [OpenSCAD] How to make a cylinder perpendicular to a
sloping face
Message-ID:
<[hidden email]>

Content-Type: text/plain; charset="utf-8"

On 9/5/2019 3:16 PM, nop head wrote:
> >I think the idea that you should use trig every time you want to
> position an object is absurd.???
>
> Well for me trig is trivial but I have no idea what that BSOL code
> does, or how it works. I would have to look it up but I know what
> atan2 does.

Yeah, that's pretty much my attitude too.? I know the trig, more or
less; I'd have to learn the library.? It means I reinvent wheels, but
sometimes reinventing a wheel is easier than trying to understand how
somebody else's wheel works.

You can make it a little simpler (in some ways) by embedding the
rotation and translation in the "parent" object and applying them to
children.? In a couple of cases I've had models with "faceplates" on
which there are controls; the design I've used is to accept a child that
contains objects that are to be placed on the faceplate.? The child
objects - knobs and whatnot - are laid out as if they were on a
horizontal surface at z=0; the parent rotates and translates them into
the right place.

That's basically the "attachment" model that some libraries support, but
without any attempt at generalizing.

On these models of a washing machine and a drier, the control panel
(with the buttons and knobs) and the detergent door (on top of the
washer) are done this way.? Partly it makes it easier to think about the
layout, but also the basic box for the two is the same module; it's only
those two add-ons that are specific.


I don't remember why one of the controls on the drier is white.

I've used similar strategies for positioning handles on cabinets,
separating the design of the handle from the positioning (and
duplication!) on the cabinet.

More than you wanted to know.
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Message: 2
Date: Sun, 8 Sep 2019 19:32:15 -0700 (MST)
From: adrianv <[hidden email]>
To: [hidden email]
Subject: Re: [OpenSCAD] How to make a cylinder perpendicular to a
sloping face
Message-ID: <[hidden email]>
Content-Type: text/plain; charset=us-ascii

Personally I find it's much easier to make a small (or large) mistake by
trying to position objects myself using translate and rotate operations and
doing trig.  And much harder to debug the mistake.  And harder generally to
change the model when I want to change it.  But it's obviously a matter of
opinion.   Yes, using a library does require the additional effort of
learning to use the library.   Many vocal people on this forum do not
believe that this effort will be repaid.  I personally disagree. 

Out of curiosity, how might your original query be answered with a method
that does not require learning something new?  How could a mechanism allow
you to position a cylinder on the sloped side of an object without
complicating OpenSCAD?  I am not able to imagine a mechanism that could do
this that wouldn't require learning a bunch of new commands for managing
that position. 


Robin2 wrote
> Interesting. Thank you very much.
>
> I can see how it works, but it also seems to me that it starts to lose the
> ease-of-use advantage that Openscad has over Freecad or SolveSpace. The
> library introduces a whole lot of additional stuff that must be learned
> and
> with which it is easy to make a small mistake.





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------------------------------

Message: 3
Date: Mon, 9 Sep 2019 00:25:02 -0700 (MST)
From: Robin2 <[hidden email]>
To: [hidden email]
Subject: Re: [OpenSCAD] How to make a cylinder perpendicular to a
sloping face
Message-ID: <[hidden email]>
Content-Type: text/plain; charset=us-ascii

adrianv wrote
> Out of curiosity, how might your original query be answered with a method
> that does not require learning something new? 
>
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> http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org


I agree completely. I had just been hoping that there was a simpler Openscad
solution that I was not aware of - especially as it seems so much an
integral capability of Freecad and SolveSpace

...R



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Re: Discuss Digest, Vol 58, Issue 8

Robin2
jim_klessig wrote
> From my point of view, it comes down to the fundamental difference in the
> conceptual way Fc and openscad work. In FC, you have an object from which
> you can "grab" a face, a line, or a point, and do something to it, or in a
> specific relationship to it.In Openscad, there really is nothing to
> "grab".

I do understand the difference and I find the way Openscad works suits my
"brain" better. Nevertheless the absence of the easy ability to relate one
object to the face of another seems like a significant shortcoming. At the
same time I have no idea how to deal with it. Perhaps it is just impossible
given the way in which Openscad models are defined.

Of course there is a great deal that can be done with Openscad without
needing this capability. And maybe there can be a workaround by creating the
object on the face first - while the face is known to be in a standard
plane.

...R





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