I see the latest changes from Mario Luzeiro and Oleg Endo. Wow .. the 3D viewer has improved so much since Mario and I rewrote the code 6+ years ago. I'm very glad to see people continuing to make improvements. If anyone has time and wants a challenge there are 2 items I'm not very happy with in the 3D system. One is due to our early support for VRML only models as well as IGES models, and the second issue is due to mistakes I made in interpreting the VRML specification.
1. Legacy issue: the import of a VRML model (including those exported by kicad) or an IGES model results in a doubling of the triangular surfaces. So if you import a box described by 12 triangles that is double to 24 and if you export the model and import it again you get 48 triangles, and so on. The reason is that every facet is rendered from *both* sides and there is no algorithm for decimating the triangle data. The reason triangles were rendered from both sides is that many (well, *most*) VRML models which we used before the 3D overhaul were defective and the viewing normals were not guaranteed to be correct (a facet described as viewable from the wrong side). IGES models also suffer this problem because the specification does not provide a requirement of a 'right-hand rule' to determine the Inner side vs Outer side of a surface and various CAD packages seemed to either use a right-hand rule, left-hand rule, or no rule. The triangle bloating problem will obviously have disastrous consequences for rendering time. As an alternative to decimating the triangles, any VRML model exported by KiCad could be specially tagged (similar to how PDF uses some special comments) so that the importer does not double the triangles. The advantage of this would be that the VRML models generated from solid models via scripts could also be tagged and the doubleg could be avoided altogether where appropriate. 2. Incorrect interpretation of VRML spec. This is really a fairly minor issue and I don't believe there is any evidence that it has an impact on VRML models generated from solid models via OpenCascade/FreeCAD. Unfortunately I can't remember the exact problem now, but at least one of the VRML groups are not correctly implemented and as a result cannot be correctly referenced by more than 1 other group. Fixing the implementation could produce a more efficient exported model in some use cases. Cirilo _______________________________________________ Mailing list: https://launchpad.net/~kicad-developers Post to : kicad-developers@lists.launchpad.net Unsubscribe : https://launchpad.net/~kicad-developers More help : https://help.launchpad.net/ListHelp
