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Mail Archives: geda-user/2013/06/14/19:25:22

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Date: Sat, 15 Jun 2013 01:23:19 +0200
From: Milan Prochac <milan AT prochac DOT sk>
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To: geda-user AT delorie DOT com
Subject: Re: [geda-user] 3D modelling and gEDA
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On 14. 6. 2013 20:50, Kai-Martin Knaak wrote:
> I am not a particular fan of VRML.

Me too. VRML is really horrible format by design. It tries to be 
friendly to hardware renderers (I guess) and it lacks lot of features.

My plan was to visualize the PCB design. The VRML was chosen due its 
simplicity and possibility to examine nearly-realistic 3D model in real 
time. Other options - like HQ  renderers (povray) or 3D modeller 
software - were not so straightforward, as they required offline 
rendering for each view or required additional software (and some extra 
knowledge to get some results from it).

Additionally, the simplicity of VRML made it good candidate for my first 
3D export filter, as it was quite easy implement it.

>   More often than not, when I import VRML
> models into 3D CAD applications, the result was less than perfect (Autocad
> Inventor, Varicad, solid works). Round surfaces are pieced together by
> literally thousends of triangles. The object is represented by its
> combined outer surface rather than by a set of basic object that combine
> with boolean operations. My ad hoc explanation is, that this format is
> specifically geared toward "virtual reality".

The problem is that most of VRML exporters produce VRML models created 
from triangles. VRML format defines basic primitives like cube, 
cylinder, sphere - but they are not used in that case. As the complete 
CSG is missing in VRML, there is no other way to export composite object 
from CSG capable 3D modeller.

VRML should be considered as final format (like PDF) meant for viewing 
or printing. It is not suitable for further processing, importing or 
modifications.

> I'd be more than happy to see a lossless path from pcb to a open sourced
> 3D CAD application and back. This would raise the level of awesomeness of
> geda by an order of magnitude!

Generally,  the PCB design and generic 3D modelling are very different 
worlds. The path PCB -> 3D modeller is not so hard, but the opposite way 
is almost impossible, I guess.

Well, the VRML export filter is real piece of working code (I will offer 
patch on  Launchpad next days). It is capable to export the board 
design, populate it with components, it has some fancy features - it can 
create the the models on fly, adjust description or color, change 
position, combine IC with socket or transistor with cooler.

It can be used as inspiration or base for another 3D export filters. I'd 
be happy to assist.

The real pain is component library. I am not very satisfied with my 
current solution, as it is format-specific (each format requires its own 
models or generators). I am playing with the idea to define models in 
some high level (but simple) meta-language, which would be easily 
translated to target format. And as next step ... the whole board could 
be exported by generic "3D export filter" in that meta-language and 
converted into format of your choice afterwards...

But it is all one-way road.

Milan

> ---<)kaimartin(>---

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