3 ms·

CNC and 3d printing typically use G-code, which has dedicated arc commands (G2, G3), and the laser cutter in the article uses PDF, which (apparently) does not,

CNC and 3d printing typically use G-code, which has dedicated arc commands (G2, G3), and the laser cutter in the article uses PDF, which (apparently) does not, and is the main point of the article. Of course any physical machine is only making an approximation of a circle (even a lathe doesn't turn perfectly round, there is no such thing), but at least for CNC and 3d printing you can specify a perfect circle. In PDF you can't. (Yes, it is also true that a typical 3d print comes from an STL file, which can only specify triangles, so STL files also can only specify approximations of circles. But it is still true that most 3d printers run G-code, not PDF.)

defrost 3y ago
The PDF format was intended to be an explicit per page device independant description of text, line path, and image layout subject to clipping with no "program running" elements to it. It followed PostScript which was a programming language that was intended to be directly undertood and runnable by Postscript enabled printers. Postscript could easily do the job here, it had "arc" drawing primitives that described circles (both full and partial). The 'failure' of Postscript was that as a programming languge a bad .ps job could crash a printer and a 1,500 page .ps document had to be internally fully rendered just to print out page 73 only (potentially code on any 'page' could loop back or forward and generate image elements on any page). As a not-quite PostScript simplified 'other' the PDF formal languaage spec only allows the drawing of lines and 'curves' and curves are explicitly 3rd order bezier splines. See: Path Operators (Page 95) Portable Document Format Reference Manual (230 pages) https://opensource.adobe.com/dc-acrobat-sdk-docs/pdfstandards/pdfreference1.0.pdf https://opensource.adobe.com/dc-acrobat-sdk-docs/pdfstandard...
- hinkley 3y ago
  SVG would likely be a better target today.
hinkley 3y ago
> even a lathe doesn't turn perfectly round, there is no such thing You don’t have to look for long on YouTube to find videos showing lathe tolerances of ten mil or lower. And things like bearing races, where imperfections are a common failure mode, are turned for polishing if nothing else.

defrost 3y ago

The PDF format was intended to be an explicit per page device independant description of text, line path, and image layout subject to clipping with no "program running" elements to it. It followed PostScript which was a programming language that was intended to be directly undertood and runnable by Postscript enabled printers. Postscript could easily do the job here, it had "arc" drawing primitives that described circles (both full and partial). The 'failure' of Postscript was that as a programming languge a bad .ps job could crash a printer and a 1,500 page .ps document had to be internally fully rendered just to print out page 73 only (potentially code on any 'page' could loop back or forward and generate image elements on any page). As a not-quite PostScript simplified 'other' the PDF formal languaage spec only allows the drawing of lines and 'curves' and curves are explicitly 3rd order bezier splines. See: Path Operators (Page 95) Portable Document Format Reference Manual (230 pages) https://opensource.adobe.com/dc-acrobat-sdk-docs/pdfstandards/pdfreference1.0.pdf https://opensource.adobe.com/dc-acrobat-sdk-docs/pdfstandard...

hinkley 3y ago
SVG would likely be a better target today.

hinkley 3y ago

> even a lathe doesn't turn perfectly round, there is no such thing You don’t have to look for long on YouTube to find videos showing lathe tolerances of ten mil or lower. And things like bearing races, where imperfections are a common failure mode, are turned for polishing if nothing else.