Hi Csaba,
Regarding the revolve primitive: It was implemented by Timothy Van
Ruitenbeek during GSoC 2009. You can find his development log here:
http://brlcad.org/wiki/User:Pacman87
Effectively only the line segments are functional. The circular arcs
are half implemented (no output yet), and the implementations for
Bezier curves and NURBs are missing.
Regards,
Daniel
2014-03-01 23:02 GMT+01:00 Csaba Nagy <[email protected]>:
> Hi all,
>
> It seems that the sketch support in BRL-CAD is very buggy or perhaps not
> fully implemented... I would like to get an informed opinion on the
> status quo.
>
> While wrapping the Sketch/Extrude/Revolve primitives in python-brlcad, I
> did some tests to understand how it works. The net result is that I
> barely managed to get any of the sketches I created to properly extrude
> or revolve...
>
> For the Extrude part, after a quick code check I concluded that support
> for NURB segments is not coded at all, they are simply ignored... also
> the CARC segments are buggy, some work some not.
>
> The Revolve primitive - I could not get it work with anything else than
> line segments. Even with those I'm not sure what are the requirements
> for the resulting shape to raytrace properly, for example it's not clear
> what happens with points on the revolution axis. It seems that the first
> and end points will be automatically closed with a disc even if they are
> not on the axis.
>
> Also some of the parameters are ignored, or at least it seems so, and
> others I modified but the effects were not consistent...
>
> I uploaded one of the tests I made, ray-trace revolve.s to see one of
> the failures:
>
> http://pastebin.com/kJppsgyK
>
> Generally where can I find some documentation of how it works in
> detail ?
>
> In fact I would go further and ask if the existing primitives would
> perhaps be enhanced by:
>
> * 3D path (to allow curves in space);
>
> * extrusion along a path -> this would cover both extrusion (linear
> path) and revolution (circular arc);
>
> It seems that other CAD projects implemented/discussed this:
>
> http://wiki.blender.org/index.php/Doc:2.4/Tutorials/Modeling/Curves/Extrude_Along_Path
>
> http://www.we-r-here.com/cad/tutorials/level_3/3-7a.htm
>
> https://github.com/openscad/openscad/issues/114
>
>
> So what is the status quo in this area ? Is there any existing effort
> which is not already in the primitives code ?
>
> Implementing some of this could be an interesting GSOC project too. I
> would also like to have a stab at it but my attention is currently on
> the python-brlcad project and time is limited...
>
> Cheers,
> Csaba
>
>
>
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