Better imprint for assy - #2069
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@jmwright would you be able to take a look? |
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This MRE:
import cadquery as cq
from cadquery.occ_impl.assembly import imprint
imprint(cq.Assembly().add(cq.Workplane().box(1, 1, 1)))gives this error:
Traceback (most recent call last):
File "<python-input-4>", line 1, in <module>
imprint(cq.Assembly().add(cq.Workplane().box(1, 1, 1)))
~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/jwright/repos/cadquery/cadquery/occ_impl/assembly.py", line 885, in imprint
res = Shape(builder.Shape())
File "/home/jwright/repos/cadquery/cadquery/occ_impl/shapes.py", line 445, in __init__
self.wrapped = downcast(obj)
~~~~~~~~^^^^^
File "/home/jwright/repos/cadquery/cadquery/occ_impl/shapes.py", line 419, in downcast
f_downcast: Any = downcast_LUT[shapetype(obj)]
~~~~~~~~~^^^^^
File "/home/jwright/repos/cadquery/cadquery/occ_impl/shapes.py", line 409, in shapetype
raise ValueError("Null TopoDS_Shape object")
Co-authored-by: Jeremy Wright <wrightjmf@gmail.com>
Imprint needs at least 2 shapes to do something meaningful . The previous version does not indeed throw, I'll add an explicit check for this. |
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Done, I also added a check for no solids at all. |
The zoo had no model where two solids meet over part of a curved surface.
Every existing multi-solid model either shares an exactly coincident face,
because the enclosing body was cut by the same primitive, or does not touch at
all. Partial contact on a curved surface is the case that separates OCCT's
gluing options, so add two models that cover it.
TwoAnnularSectors puts a shorter sector directly outside a taller one, both
spanning the same 90 degrees. The contact patch is a band that reaches the
angular edges of the first sector's outer face, so the imprint edges run clean
across that face. Every gluing option handles this, which makes it the control
case.
TwoAnnularSectorsPartialArc makes the second sector narrower as well as
shorter, so the patch is strictly interior to the first sector's outer face and
reaches its boundary in neither the axial nor the angular direction. Imprinting
then has to split the larger curved face around an island:
glue solids shared faces shared area
full 2 0 0
partial 2 1 23.5619
None 2 1 23.5619
The shared area matches the analytic 6 * radians(45) * 5. Full gluing returns
the two solids with no shared face at all, so the DAGMC model would not be
watertight at that interface. This is the geometry that shows why partial is
the right default, following CadQuery/cadquery#2069.
Solid volumes are analytically exact, 212.0575 and 176.7146 for the band model
and 212.0575 and 88.3573 for the partial arc model, and the CSG regions agree.
Both models reproduce their CSG reference under the gmsh mesher, to 0.01
percent on material 1 and 0.10 percent on material 2.
Adds the models, tests for both suites, examples, preview images and README
entries. Both fail under the tolerance and angular_tolerance meshing path with
about 19 percent error on material 2, which is the same cad_to_dagmc defect
described in the parent pull request and not a property of these models.
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I am now using this feature and it is super useful. I have a use case where I have some CQ geometry and I don't know if I can get away with 'full' imprinting (which is fast but can be wrong) or if I need 'partial' imprinting (which is slower but always correct). The CQ models are large and prepared upstream so without a lot of inspection I'm never going to know if I can go for full imprint in some surfaces. Is there any possibility of having another mode 'auto' which know when 'full' can be used and 'partial' is necessary. For example can we use check the faces/edges and somehow conservatively identify fully coincident contacts or partial face overlap |
I'm not an OCCT expert but according to the docs isn't glue faster because it skips computations based on assumptions up front? If you run these computation in 'auto' mode then doesn't that move a time consuming part to a different function? |
4 participants
Low level fix enabling faster imprints for well behaved models.
NB: this PR also contains a typing fix related to Numba version update.
Tangentially related to this PR (I added explicit test for this use case) - it is possible to imprint subassemblies separately and on per subassy basis use different imprint glue settings in order to optimize performance: