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Re: VRML export issues


----- Original Message -----

> From: jp charras <jp.charras@xxxxxxxxxx>
> To: Cirilo Bernardo <cirilo_bernardo@xxxxxxxxx>
> Cc: Kicad Developers <kicad-developers@xxxxxxxxxxxxxxxxxxx>
> Sent: Sunday, January 20, 2013 11:06 PM
> Subject: Re: VRML export issues
> Le 20/01/2013 10:50, Cirilo Bernardo a écrit :
>>  Hi Jean-Pierre,
>>    I was looking at the VRML exports again and I noticed some inconsistency 
> on what side a feature is visible from. For example, I wrote in a previous email 
> that only the first pad of each DIL package seemed to be rendered even though 
> all pads of resistors, diodes, and a few other components seemed to be rendered 
> correctly.
>>    The other pads of the DIL packages were in fact rendered but they are 
> visible from the bottom side; these pads are oval while all the circular and 
> rectangular pads are visible from the top side. I had a closer look at the code 
> and the features seem to be rendered visible from the same side (but which side 
> they are visible from is a matter of chance) regardless of the layer which the 
> feature appears on.
>>    One way to solve this of course is for features to have a thickness and 
> be rendered so that they are visible from both sides. Would this be an 
> acceptable solution?
>>    At the moment the board substrate itself is not rendered; if it is 
> rendered then should we only render feature on the top and bottom copper layers 
> and on the silkscreens? After all, once the board is rendered we cannot see 
> inside it.
>>    Should the board substrate be rendered or not - or should this be 
> configurable? If the board is rendered, should we place holes in the board ( I 
> suspect we will need to, which makes the board rendering fairly complex and also 
> requires a lot more data points in the VRML file).
>>    I also noticed that the pads do not seem to have holes in them - is this 
> a bug in the code or are all pads solid but thru-hole pads have a drill 
> coordinate specified in addition?
>>    I will ask on the users list how people use the exported VRML file to 
> find out if people want the board rendered like the final product or if they 
> want it see-through for inspecting things.
>>  Regards,
>>  Cirilo
> I am *not* a VRML specialist.
> However I am thinking the VRML export has a main issue:
> - board items (pads, tracks, vias ) are exported as 2D objects. A 3D 
> object is more complex.
> I explain: when exporting a rectangular pad, currently, the exported 
> item is just a quad ( a rectangular area).
> I am thinking a pad should a 3D shape with a thickness ( the copper 
> thickness: usually 15 to 70 micrometers),
> with a front side, a back side, an 4 sides, each having its orientation 
> to reflect light.
> Therefore when a 3D object is exported as a 2D object, what you see 
> depends on the VRML  viewer internal code,
> and the orientation of the shape.
> Pads with holes are exported as a 2D shape with no hole + a cylinder 
> (the hole): could be a bug inside the code.
> Perhaps  Lorenzo Mercantonio ( who wrote the code ) could explain better 
> than me what should be enhanced.
> -- 
> Jean-Pierre CHARRAS

Thanks Jean-Pierre,  I'll work on all that in my spare time.  I'll see if Lorenzo has any comments.

- Cirilo