Previously, the default extruder wasn't handled inside multi-material segmentation, but this could confuse users, especially for multi-volume objects.
Because with multi-volume, it could happen that in the place where two volumes were touching, there could be a change in the used extruder.
This new implementation should resolve several types of artifacts with multi-material segmentation.
It should also increase the precision of projection, so sliced models should be much closer to how they were painted.
Also, the slicing of painted models should be faster than before.
Previous algorithms assume that they can get an invalid Voronoi diagram. Because of that, during the multi-material segmentation, a copy of the Voronoi diagram was created, and there were several attempts to fix missing vertices and edges. But as it shows, this wasn't a good enough approach and sometimes led to several issues like bleeding layers.
After generalization, our approach for detection and repairs of invalid Voronoi diagrams from Arachne, we could assume that multi-material segmentation gets non-invalid Voronoi diagrams.
With this assumption, we reimplement multi-materials segmentation to work directly on the Voronoi diagram. That should make multi-material segmentation more stable.
So, this should fix several issues like bleeding layers. Also, memory consumption should decrease by a lot. Also, there should be some speedup of multi-materials segmentation.
into a graph with links to the layer above / below.
In addition:
Members of LayerRegion were made private, public interface const only.
this->m_xxx replaced with just m_xxx
SurfacesPtr was made a vector of const pointers.
https://github.com/tcbrindle/span
Replacing a homebrew const pointer wrapper const correctness helper
with the C++20 like span library.
One day when we switch to C++20 we will just use the C++20 spans instead.
The main contribution of the smooth_outward function for multi-material segmentation was the removal of duplicate points in polygons using MutablePolygon::remove_duplicates().
But the issue with this function is that it deletes points only based on their distances, which could cause problems like in #7838.
Previously, colored polygons were stored so that each polygon had a color assigned to it, which made it difficult to perform operations like union or so on all polygons of the same color. Now polygons are stored grouped by their assigned color/extruder.
for offset2() with clear meaning.
New ClipperUtils functions: expand(), shrink() as an alternative
for offset() with clear meaning.
All offset values for the new functions are positive.
Various offsetting ClipperUtils (offset, offset2, offset2_ex) working
over Polygons were marked as unsafe, sometimes producing invalid output
if called for more than one polygon. These functions were reworked
to offset polygons one by one. The new functions working over Polygons
shall work the same way as the old safe ones working over ExPolygons,
but working with Polygons shall be computationally more efficient.
Improvements in FDM support generator:
1) For both grid and snug supports: Don't filter out supports for which
the contacts are completely reduced by support / object XY separation.
2) Rounding / merging of supports using the closing radius parameter is
now smoother, it does not produce sharp corners.
3) Snug supports: When calculating support interfaces, expand the projected
support contact areas to produce wider, printable and more stable interfaces.
4) Don't reduce support interfaces for snug supports for steep overhangs,
that would normally not need them. Snug supports often produce very
narrow support interface regions and turning them off makes the support
interfaces disappear.
