Fixes Slicing slows or hangs on "Generating Permiters 20%" cpu load is at 100% #8164
Fixes Slicing hangs on generating perimeters with thing:3565827 (30g) #3259
1) Removed virtual methods. There was not really need for them.
2) Some of the virtual methods were using conversion to Lines, which
was unnecessary and expensive.
3) Removed some nearest element search methods from Point.
Implementation of extra perimeters on steep overhangs/flat unsupported parts
Also contains:
Principal components computation over polygon area
New fast bridge direction estimation which minimizes amount of unanchored bridge endpoints
Refactored PerimeterGenerator for functional style, better constness
with the goal of calling PerimeterGenerator::process_xxx()
for each surface at once to collect its fill expolygons.
That allows computed better values in cases when the extrusion width of the first layer or for the infill differs from the extrusion width for perimeters.
Parameters min_feature_size and wall_transition_length now can be set in percentages, and then they will be calculated based on nozzle size. Old profiles with default values are forced to replace old default values with new default values in percentages.
The previous behavior didn't merge two ExtrusionPaths with the same extrusion width, and it also could merge two ExtrusionPaths with different widths, which was unintentional, and it could also possibly create visible artifacts in some cases.
Because simplification of ExtrusionLoop in GCode::extrude_loop is working on ExtrusionPath and not on whole ExtrusionLoop, so previous incorrect behavior was preventing simplification and removing small extrusions like in #8455.
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.
Fixes Solid infill where there should be none #6482
Also the safety offsetting was revised to be enabled only where needed,
the "do safety offset" is now easy to discover by
a new ApplySafetyOffset::Yes enum, and safety offset over union, which
is better done by offset() / offset_ex() has been replaced with
new union_safety_offset() / union_safety_offset_ex() functions, which
better convey their meaning and which could be better optimized than
union() with the safety offset applied.
