Render G2/G3 arcs in 3D view by interpolating them as line segments

[IgorYeremin]

No description provided.

[kliment]

@IgorYeremin thank you for your contributions!

@volconst could I have your thoughts on this and Igor's other two active PRs? They look good to me but I would like your opinion before I merge them.

[volconst]

@kliment , Sorry for the delay, I have missed it's referencing me.
@IgorYeremin , can you upload/link a test file.

[IgorYeremin]

Sure! I'm testing Marlin on a plasma machine, so here are gcode files generating using Fusion360.
One file uses M3 to turn cutter on (would render as travel without my other patches), the other one uses E moves, so it should work as is.

test-fusion-plasma-arcs.zip

[volconst]

@IgorYeremin do you have uncommitted changes in your work dir, I am getting exception:

Loading file: /home/.../test-fusion-plasma-arcs/test-fusion-plasma-m3.gcode
Loaded /home/.../test-fusion-plasma-arcs/test-fusion-plasma-m3.gcode, 657 lines
0.00mm of filament used in this print
...
Traceback (most recent call last):
File "/home/.../Printrun/printrun/pronterface.py", line 1605, in loadviz
generator_output = next(generator)
File "/home/.../Printrun/printrun/gcview.py", line 333, in addfile_perlayer
generator_output = next(generator)
File "/home/.../Printrun/printrun/gl/libtatlin/actors.py", line 472, in load_data
for gline_idx, gline in interpolate_arcs(layer):
File "/home/.../Printrun/printrun/gl/libtatlin/actors.py", line 349, in interpolate_arcs
mid = copy.copy(gline)
File "/usr/lib/python3.7/copy.py", line 96, in copy
rv = reductor(4)
TypeError: 'NoneType' object is not callable

[IgorYeremin]

I do not have uncommitted changes in my work dir.
Did you run python setup.py build_ext --inplace to recompile the modified gcoder_line.pyx?

[volconst]

No, maybe the python class needs changes

[volconst]

I am not using gcoder_line.
WARNING:root:Memory-efficient GCoder implementation unavailable: cannot import name 'gcoder_line' from 'printrun' (/home/.../Printrun/printrun/init.py)

[IgorYeremin]

Ah ok, didn't realize you can run without Cython, here's the copy function for PyLine

[volconst]

Copying and translating G2 Arc commands and pretending they are lines is neither semantically, nor performance-wise desirable. Would make sense only if we have to fool some foreign interface we do not control. Fortunately the site of consumption of interpolate_arcs is in the same file.
Here it's seen that the only value/information that we add is tuple(current_x, current_y), which a better candidate for return value
I think the clean way is to add a separate inner iteration loop which eventually expands glines to points, so we have both access to the original gline and the interpolated points, without copying.
The indisputable advantage of the current setup is that it exists and works :)

[volconst]

@kliment Let's merge #1092, #1093, #1094 .
@IgorYeremin thanks for these contributions

[kliment]

@volconst okay, I'll merge them, thank you for reviewing