BooleanDifference failure

I have a lot of trouble with BooleanDifference. I’ve attached an image and file of my latest roadblock. I’m attempting to subtract the red from the grey with no luck. Any suggestions? I’ve used all the same linework, so edges,surfaces, etc. should line up.

plastic.3dm (317.7 KB)

Hi @james.f.markel
Rhino never was great at too many coincident faces when doing booleans, and you can actually see the z-fighting in your screengrab. Either construct a boolean operator with a little overlap (even if it’s just for the sake of the boolean operation) or - as I did here - trim/split/join the whole thing manually, which only takes a minute or two.
HTH, Jakob
plastic JANO.3dm (245.5 KB)
Edit: I agree that it would be nice, if this just worked “out of the box”, but it’s fairly simple to do manually.

Hi @james.f.markel
This might help what Jakob @Normand described:
Regards. ~Fred

@james.f.markel Hi James - as pointed out, Rhino Boolean operations do not do well with coincident surfaces - with the exception of coincident planes, those are handled pretty well in general. You can use this to your advantage and at the same time clean up your geometry so that is it more exactly what (I am guessing) you intend.

From the look of it, the sections of these two objects are, in theory, made up of tangent arcs and lines. In fact the sections are pretty much arc shaped and line shaped, but if I am correct as to the intention then I recommend making them exactly as they should be. In the attached file, I’ve reconstructed the section curves with true arcs and lines - this is not only more exact, it makes the geometry much simpler - arc/cylinder shaped faces and planar faces with no ambiguous kinda-sorta shapes. In the context of the particular problem you’ve run into, what this means is that you end up with exactly planar faces coinciding with other planar faces and not hitting the arcs at all - so the Boolean operation can work and give clean reasults.

plastic_PG.3dm (437.9 KB)


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Thank you for the file Pascal. I’m not sure why the sections weren’t lines and arcs to begin with, as i used those tools, as i used those tools when drawing the figure, but your advice is duly noted.