Boolean union fails on valid geometries

Hello,

I want to use bath-like geometry to substract from the bigger one. The problem is that the tool doesn’t work. It behaves stange. I checked the objects: Rhino says they are valid, yet the boollean difference doesn’t work like it should.

Bath-like geometry created from two objects:

Bigger polysurface

The result of boolean difference

I thought that the cutting objects may not touch, but this is not the case. I tried to union them but this operation failed.

I tried to raise the lower object by 2mm so they would definitely have a common area, but this gave me this error:

Boolean_difference_problem.3dm (177.6 KB)

I used the option “check” on the rounded polysurface. It reported: “not valid”
I used to command to find bad surfaces, 2 were find and I deleted them. Then I used “Cap” and run “Check” again. This time the object was valid but it didn’t solve my problem.

I would be grateful for help. I guess there is something wrong with the geometry but I don’t know how. All I did was to “Sweep” a profile around the rounded rectangle.

the 2 lower / inner solids are not precise enough

and boolean difference does not like tangential / coplanar stuff…

but you can solve it with trim / join. (which was not necessary in the end…)
but a 180-Degree edge might give you later problems…

_crvDeviation is a nice Analysing tool to see wether Edges precise.

why do you have this fancy radius of 0.171109 ?

(EDIT:)

after building a precise version of the green part, booleanDifference works:

for rebuilding the green part I used:
_boundingbox
_scale1d (copy yes) - for the lower rectangular part…
_radius (to measure your initial radii)
_filletEdge
_booleanUnion

Boolean_difference_problem_tp.3dm (396.3 KB)

hope this helps - kind regards -tom

2 Likes

Thank you @Tom_P for such a quick response. I tried to recreate your actions but I miserably failed. That makes me even more grateful for the file you attached to your post. I will try to figure it out during the weekend.

You asked why I have this strange radius. I model from a point cloud and that is the shape of the real world object which I am supposed to recreate. I wanted to substract the violet “baths” from these big, concrete area.

3D view

section views

I am very grateful for your help :slight_smile: