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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.


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

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