On Sun, Oct 13, 2013 at 06:04:46PM -0000, Daniel Santos wrote: > Hmm, while I'm not certain, we may be talking about the same thing, but > from a different standpoint. I don't see any reference in the gerber > spec to the word "raster". If you are talking about drawing straight > lines with an apeture to to rasterize your own image, I'm wondering if > this falls into the catagory of "stroke painting" which unamco is > claiming to be "harmful" (see the PDF named "Gerber File Format: > Painting Considered Harmful" on the page > http://www.ucamco.com/downloads.aspx).
Yes, that is however referred to copper pours. It is indeed a deprecated way to fill zones (however pcbnew still supports it), mainly because it's difficult to handle with CAM processors, to check netlists and fabrication rules. However text is (hopefully) far from copper areas or on the silkscreen so it doesn't suffer from these drawbacks. The main problem with area fills with fonts it the model used to represent outlines and suboutlines (i.e. internal cutouts); the font model uses the common 'postscript' model: - Outlines are described with lines, quadric and cubic curves, depending on the font: truetype uses quadrics, Type1/CFF uses cubics; lines are represented as the obvious degeneration of said curves; orientation of the (sub)outlines is consistent and mandatory (I don't remember the details); - Sub-outlines are handled closing the current outline and opening a new one. Inner area is described (IIRC) using the winding rule (need to check for details on this and on self intersecting outlines). If you ever used Corel Draw/Adobe Illustrator/Inkscape that's the usual graphic model for handling outlines. Gerber instead uses a way different (and simpler) model for outlines: - Outlines are described with lines and circular arcs (as different primitives), orientation is not defined nor required; - There are no suboutlines, internal cutouts have to be represented with a zero-width isthmus cutting thru the filled area to the cutout. Page 49 better explains that. The most similar thing I can think of are autocad polylines and shapes. In fact SHP/SHX fonts are described exactly as polylines and I actually have a working converter from SHP to the Hershey encoding used by kicad (my ISO branch uses an hand-tuned version of the ISOCP font). The first difference is easily handled approximating the curves with lines (fun fact: the bezier curves used by fonts can't actually exactly describe circular arcs, which are the only gerber supported curves). However the difference on suboutlines need to be resolved with a numerically stable way to find a good point to cut the filled area: think about the eye in the R glyph: you need to find a non self-intersecting line connecting the perimeter with the eye (the @ glyph is left as an exercise:D). The stability condition is needed because the entry line and the exit line must be exactly overlapped to avoid artifacts (remember: they can't self intersect so they must be the same!). I'm not saying it can't be done but needs considerable computational geometry experience (which I don't have...i.e. I haven't a good idea on how to do it in the general case). > However, it was my understanding that a modern photoplotter would take > your contour regions and rasterize them to produce the final output, > leaving you to just draw what you need in as simple of terms as possible > and let the plotter rasterize it. Please correct me if I'm > misunderstanding something here. Yes, the plotter give you a (polyesther, probably) film with these characteristics. However usually the film simply produces an images over a coarse grid of wires (which can even have 0.2mm pitch with some processes!). Look here http://en.wikipedia.org/wiki/File:Ssc.jpg There are different, more expensive, processes which gives you better resolution, of course. Anyway all the board I've seen screened with a non-vector font had the raster shapes quite visible under magnification (you see the round line caps on the left and side of the letters), so I'd assume that's the industry standard practice. The idea of using gerber fills for filling glyphs is interesting anyway, let me know if you manage to handle that. -- Lorenzo Marcantonio Logos Srl -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/668145 Title: Font preferences not available anymore, internal font changed To manage notifications about this bug go to: https://bugs.launchpad.net/kicad/+bug/668145/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
