Re: [Sodipodi-list] Using Sodipodi for 2-D CAD/CAM.

[Lars Clausen <lrclause cs uiuc edu>]

On Monday, 23 September '02, C. Scott Ananian wrote:
> On Mon, 23 Sep 2002, Alan Horkan wrote:
> 
>> Dia is a Vector graphics diagramming tool, and it more intended for the
>> the kind of design purposes you mention than the kind of beautiful
>> artwork you can produce with Sodipodi.
>> 
>> I am surprised that you did not even consider it, did you not hear about
>> it or is it not appropriate?  Dia
>> http://www.lysator.liu.se/~alla/dia/
> 
> I'd heard of it, but it didn't come to mind when I was drawing up my list.
> I've taken a look at it now.  Perhaps you can help me, because I can't
> seem to make Dia:
>   1) precisely dimension an object.  How do I get a box which is exactly
>      2mm by 4mm, for example?

Except by using snap-to-grid, there is no way to do this currently.  We're
looking into adding low-level properties such as size and position into the
properties dialogs.

>   2) snap-align objects.  How could I get the top left corner of a box to
>      exactly match up with the midpoint of the left-hand side of another
>      box?  How can I align the center of a circle to the top-left corner
>      of a box?

There's some aligning possible in the Object menu, but not really that kind.

>   3) weld objects together (boolean addition) [also intersect and
>      subtract]  Once I've put my circle center on the corner of a box,
>      I'd like to union the shapes to get one outline around the outside of
>      both shapes.

This would be tricky to do.  The drawing process is not at all built with
that in mind.

>   4) There seems to be some amount of parametric dimensioning, in that
>      lines will follow an anchor point as it is moved, but this capability
>      is not as powerful as one would want in a 2D CAD tool.  I'd also like
>      to say, "the center of this circle is exactly 5 inches above this
>      line" for example.

More generic constraints would allow a number of interesting features, but
it seems outside of Dia's scope for now.

I don't see Dia as good for the high-precision layout needed for CAD/CAM.
It is intended to make diagrams where the structure rather than the
dimensions are the main focus.  Thus, we can allow more sloppiness than a
dedicated CAD/CAM program.

-Lars

-- 
Lars Clausen (http://shasta.cs.uiuc.edu/~lrclause)| Hårdgrim of Numenor
"I do not agree with a word that you say, but I   |----------------------------
will defend to the death your right to say it."   | Where are we going, and
    --Evelyn Beatrice Hall paraphrasing Voltaire  | what's with the handbasket?