Bad Boolean Union in V7/V8

Serengeti (Rhino WIP)
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1

In the file below, When one tries to union all of the polysurfaces, it either refuses (when all selected together), or, if you try sequentially, you can get it to union, but it it produces a bad object. The top and bottom surfaces of the main body have bad trims.

BU-BadObject-V7.3dm (1.4 MB)

image
image1424×1274 125 KB

In V8 it’s a bit worse…

BU-BadObject-V8.3dm (3.7 MB)

image
image1891×1281 97.9 KB

(the surfaces haven’t actually disappeared, the bad trims just made them invisible)

I understand that there are coincident and near-tangent edges in play here, but this is such a simple object, it really should work.

2

Hi Mitch -
On the list - RH-73000 BooleanUnion: Failure example
-wim

3

Hi @Helvetosaur,

FWIW remaking the large piece from its top surface boundary curves allows this to union ok:

image
image1026×737 133 KB

Although Check flags the result as a bad object…

[Edit: Exporting the curves (Geometry only) and extruding them in a new file and then unioning the solids results in an object that Check flags as good. Go figure.]

4

Yes, if I proceed differently, I can make it good.
Extrude just the main body outline curve with no holes 5mm both sides
Extrude solid the round and oval boss outline curves 10mm both sides
BooleanUnion all
Extrude solid the curves representing the 3 holes 10+ mm both sides
BooleanDifference hole extrusions from body

Makes a “good” object.

5

Instead of being composed of 2 arc and 2 lines, the outside profiles of each oval boss is composed of 5 lines and 3 arcs. The additional geometry mismatches the large part at the areas don’t Boolean well or at all.