Bug: Tiny gap gets ignored and replaced with infill.

[JoschaMiddendorf]

Version

1.39.1-prusa3d

Operating system type + version

macOS High Sierra 10.13.4 (17E199)

Behavior

• Describtion the problem
  • Slic3r is just generating infill where a gap should be.
• Steps needed to reproduce the problem
  • slice this part
• Expected Results
  
• Actual Results
  

STL/Config (.ZIP) where problem occurs

ConfigAndSTL.zip

[tkircher]

It's not really a bug. Features below a certain size are ignored on purpose.

[bubnikv]

No, it is an issue with the Clipper library when handling polygons with holes. The issue is similar to
#865
#676

[bubnikv]

@tkircher was right. It is the same issue as #520, slic3r closes gaps smaller than 0.01mm on purpose, as they are not really printable by the FDM technology, or at least they were not some years ago. We may either lower the threshold, or just remove it, but not for the 1.40 release.

To verify the hypothesis, lower the safety_offset in TriangleMesh.cpp, just search for
//FIXME see #520
double safety_offset = scale_(0.0001);

I am closing this issue as a duplicate of #520, this issue will be referenced from #520.

[bubnikv]

By the way, I have introduced a new parameter "slice_closing_radius", which is set to 0.049 by default, leading to the same results as in 1.41.3. If you need to maintain the thin gaps, starting with Slic3r-1.42.0-alpha7 you will need to lower the new "slice_closing_radius" value.

Implemented with e3cba0a

This parameter and the return to the 1.41.3 behavior by default was made as we have discovered some models with cracks, which were handled correctly by 1.41.3, but which were full of spurious perimeters in 1.42.0-alpha5. We find it safer to revert to the 1.41.3 behavior while giving you the parameter to tinker with.