Can't add special variables like "$fn" from python code #104

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1. etjones commented on Feb 19, 2019

   

   etjones

   on Feb 19, 2019

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   This is definitely a hole in the documentation! The most common case is, as you say, $fn. For that, you can specify a segments argument for any function (sphere(), cylinder(), etc.) that would take $fn. You can also check out the pattern in the solidpython_template example where you speficy SEGMENTS at the top of your SolidPython file, and add that as a header to the rendered SCAD code. This lets you control the segments for the entire model in one place. I've found this the easiest way to work for quick renders (SEGMENTS = 12) which I can increase for really smooth curves once I'm ready to render out (SEGMENTS = 120).

   I'll open an issue specifically to document OpenSCAD special variables and how to deal with them.
2. etjones

   closed this as completedon Feb 19, 2019
3. nickc92 commented on Feb 19, 2019

   

   nickc92

   on Feb 19, 2019 via email

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   So the $fn variable can be set on individual objects using the “segments” keyword, e.g.: sphere(1.0, segments=50) But I don’t believe there is a way to set $fn globally (Evan, maybe you can chime in if I’m wrong). It may be worth mentioning that the “viewscad” module, which lets you render solidpython stuff without the openscad GUI, allows you to set those variables: renderer.render(obj, dollar_sign_vars={‘fn’: 50}) -Nick

   …

   On Feb 19, 2019, at 6:40 AM, f varas ***@***.***> wrote: Hello, I can' t find a way to pass the value of special variables [1][2] directly from the python script, I have to re-edit the scad file manually. I'd like to have to possibility to pass "$fn=360", for example. [1] http://www.openscad.org/cheatsheet/ [2] https://en.wikibooks.org/wiki/OpenSCAD_User_Manual/Other_Language_Features#.24fa.2C_.24fs_and_.24fn — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub, or mute the thread.
4. etjones commented on Feb 19, 2019

   

   etjones

   on Feb 19, 2019

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   You're correct that there's not a programmatic way to set $fn globally. Maybe there should be?

   Here's the pattern I use (and it's in the solidpython_template example ) to specify $fn globally:

   SEGMENTS = 12
   a = assembly() # some SolidPython object
   scad_render_to_file(a, file_header='$fn = %s;' % SEGMENTS)

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