awk -f dxf-ply.awk input.dxf > output.ply 2> error.log
x1:10, y1:20, z1:30;
x2:11, y2:21, z2:31;
x3:12, y3:22, z3:32;
index = coordinate_index * dimensions + coordinate_dimension
eg:
(0.0, 0.0, 0.0) -> 0 * 3 + 0 = 0
(1.0, 0.0, 0.0) -> 1 * 3 + 0 = 3
(0.0, 1.0, 0.0) -> 2 * 3 + 1 = 7
(0.0, 0.0, 1.0) -> 3 * 3 + 2 = 11
https://web.archive.org/web/20161204152348/http://www.dcs.ed.ac.uk/teaching/cs4/www/graphics/Web/ply.html
http://paulbourke.net/dataformats/ply/
https://brainder.org/tag/ply/
http://paulbourke.net/dataformats/dxf/dxf10.html
http://paulbourke.net/dataformats/dxf/min3d.html
http://images.autodesk.com/adsk/files/autocad_2012_pdf_dxf-reference_enu.pdf
https://www.fileformat.info/format/dxf/egff.htm
Online converter: https://products.aspose.app/3d/conversion/dxf-to-ply
FreeCAD: https://github.com/FreeCAD/FreeCAD
meshlab: https://github.com/cnr-isti-vclab/meshlab