The commit rB6f63417b500d that made exact boolean work on meshes
with holes (like Suzanne) unfortunately dramatically slowed things
down on other non-manifold meshes that don't have holes and didn't
need the per-triangle insideness test.
This adds a hole_tolerant parameter, false by default, that the user
can enable to get good results on non-manifold meshes with holes.
Using false for this parameter speeds up the time from 90 seconds
to 10 seconds on an example with 1.2M triangles.
The Exact boolean used in the cell fracture addon incorrectly
kept some outside faces: due to some raycasts going into open
eye socket then out of the head, leading to one ray direction
(out of 8) saying the face was inside the head. The current
code allowed 1 of 8 rays only as "inside" to accommodate the
case of a plane used in boolean to bisect. But this cell fracture
case needs more confidence of being inside. So changed the
test for intersection to require at least 3 of 8 rays to be inside.
Maybe the number of rays to indicate insideness should be exposed
as an option, to allow user tuning according to the degree of
"non-volumeness" of the arguments, but will try at least for now
to magically guess the right value of the rays-inside threshold.
Note: all of this only for the case where the arguments are not
all PWN (approx: manifold). The all-PWN case doesn't use raycast.
Triangulating ngons could fail with the method that was being
used: projecting along the dominant normal axis and then using CDT.
It could fail if the ngon has self crossings or might be so after
the described projection.
Switched to using projection along the normal itself, and also to
using polyfill which produces some kind of triangulation no matter
what in such circumstances. This will also likely be faster if
there are a lot of ngons in the meshes, since the exact arithmetic
CDT was being used before, and now float arithmetic is used.
The Exact modifier code had been written to avoid using BMesh but
in the initial release the modifier still converted all Meshes to
BMeshes, and then after running the boolean code on the BMeshes,
converted the result back to a Mesh.
This change skips that. Most of the work here is in getting the
Custom Data layers right. The approach taken is to merge default
layers from all operand meshes into the final result, and then
use the original verts, edges, polys, and loops to copy or interpolate
the appropriate custom data layers from all operands into the result.
While Boolean is not guaranteed to work if the operands are not
volume-enclosing (technically: PWN - piecewise constant winding number),
it needs to do something in those cases. This change makes
more cases meet user expectations in T84493, T64544, T83403,
T82642 (though very slow on that one).
The original new boolean code used "generalized winding number"
for this fallback; replaced this with code that uses raycasting.
Raycasting would have been faster, but for unfortunately also
switchd to per-triangle tests rather than per-patch tests since
it is possible (e.g., with Suzanne) to have patches that are
both inside and outside the other shape. That can make it much
slower in some cases, sadly.
I thought I had reasoned that the add_patch would only happen
when the patch was not already in a cell, but I missed reasoning
about merged cells. So switched to a set 'add' instead of 'add_new'.
By checking if a cell has already been processed in the finding patch
component code, an enormous speedup happens. This only will be
noticeable if there are lots of patches, and some cells with a
large number of patches.
In case where there are coplanar instersections where
each part has a lot of triangles, the finding-cells algorithm was
very inefficient. This uses a Set instead of a Vector to keep track
of a cell's patches, avoids going through all patch x patch combinations,
avoids going through all patches to renumber after a merge, and
merges smaller patch-sixe cells into larger ones.
All this reduces the time to find cells in the cited case by a factor of 10.
Two problems were fixed. One, the code for dissolving vertices
left a face around if dissolving a vertex would leave less than
three vertices. Instead, the face should be deleted.
Two, with transformations like "rotate 180 degrees", this should
be no problem with exact, but the current transformation matrix
has very small non-zero entries where it shouldn't. Cleaning the
transformation matrix makes it more likely that user expectations
about coplanar faces will be fulfilled.
The code was trying to ignore hidden geometry when doing boolean,
which is correct when used as a tool, but not when a modifier.
Added a "keep_hidden" argument to bmesh_boolean to distinguish the
two cases.
Also fixed a bug when the tool is used with hidden geometry that
is attached to unhidden geometry that is deleted by the operation.
The code was trying to ignore hidden geometry when doing boolean,
which is correct when used as a tool, but not when a modifier.
Added a "keep_hidden" argument to bmesh_boolean to distinguish the
two cases.
Also fixed a bug when the tool is used with hidden geometry that
is attached to unhidden geometry that is deleted by the operation.
The routine to find dissolvable vertices had a check to ensure
that the vertex was exactly in line with the two neighbors.
I have convinced myself that this check is unneccesary (it was
failing with only a 1e-9 difference from 0 on a cross check),
so have removed it.
Also added code so that exact solver does the whole collection at once.
This patch allows users to use a collection (as an alternative to Object)
for the boolean modifier operand, and therefore get rid of a long modifier stack.
Well, this only fixes the example if one uses the new Exact mode,
but since that is available, seems fair to call this fixed.
Since these were not closed-volume operands, the Exact mode needed
some adjustment to the threshold used for "inside-outside" tests
for the case of deciding if the cutter is inside the other shape
for a Difference.
This is for design task T67744, Boolean Redesign.
It adds a choice of solver to the Boolean modifier and the
Intersect (Boolean) and Intersect (Knife) tools.
The 'Fast' choice is the current Bmesh boolean.
The new 'Exact' choice is a more advanced algorithm that supports
overlapping geometry and uses more robust calculations, but is
slower than the Fast choice.
The default with this commit is set to 'Exact'. We can decide before
the 2.91 release whether or not this is the right choice, but this
choice now will get us more testing and feedback on the new code.
