Converted sheets take the rule's corner relief between walls and its bend relief where a bend ends beside more of the fixed face, and a wall on part of an edge bends only where it stands. Noted under format 21; nothing new is saved.
A Convert to Sheet Metal bend point can now lie on a bend modelled with its radius (a cylinder tangent to two flat faces) or in the middle of a chamfer; either becomes one bend at the faces' virtual sharp, with the rule's radius. Holes and engravings carry over. Bend points on edges convert as before. Recorded under format 21. Tests in cmd::sheet::convert_tests; the sheet-metal guide is updated.
sheet.export_dxf writes an AutoCAD 2000 drawing with ELLIPSE and SPLINE entities for ellipses, splines and text outlines instead of chords, with curves: arcs for machines that read only lines and arcs. Perforation circles go through the same writer. Closes#1089.
Convert to Sheet Metal without bend edges refused every plate whose bounding-box diagonal reached a thousand times its thickness ("no outline on that face"), and just under that limit a hole smaller than the mesh's sag fell out of the outline and the DXF. The outline's tolerance is now at most a tenth of the thickness: a thin plate is meshed again at that tolerance. Nothing new is stored. Tests: long thin strips, sheets thousands of times longer than thick, and a strip keeping holes down to 1 mm.
The plate check compared the face outline's area (from the tessellation, so each hole was a polygon of chords) with the exact volume, and refused plates with a few small holes. Where the outline runs along a cylinder about the plate's normal it is now an arc of that circle; coaxial pieces of one radius are one wall, so a hole split into two, three or four faces is one circle. The check passes with its tolerance unchanged, and the flat pattern and its DXF carry one CIRCLE per hole (ARC for rounded corners and slot ends).
A round blank now converts too, so unfold_cut_refold_and_convert checks the refusal with a block thicker at one end instead of a rod.
Convert to Sheet Metal now takes a solid or a shelled body by its bend edges (`bends`): the faces reached from the fixed face across those edges become the sheet, keeping the part's envelope, with the flat pattern by the rule's K-factor and radius. Other edges between sheet faces are cut open. The result works with edge flanges, cuts, Unfold/Refold, the flat pattern and DXF. A conversion without `bends` is the plate conversion as before. The optional `bends` field is noted under format 17. Fixes#647.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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