No intersection possible? (between closed surfaces)

I have two objects in Rhino: a floor (green) and a rugbyball-shaped object (red).

Here is a wireframe and shaded view:

The red object is a closed surface. The green object is a closed polysurface.

In the end I’m trying to trim/cut the red object out of the green object (already tried BooleanDifference, Trim, Split, BooleanIntersection; although not all of those have the desired end-effect).

Using the Intersect-command, Rhino couldn’t find any intersections.
However, looking at the drawing, the objects clearly intersect.

Why does Rhino think they don’t intersect?
And how can I make the intersection?

Thanks in advance for the advice!

(drawing is attached)
no intersection possible.3dm (191.3 KB)

Which version of Rhino are you running? Here on 5.12 I get two intersection curves.

Next question, how did you make the red object. The What command says it’s a revolve but seeing that there is a seem going all the way around, I’m wondering if you revolved a closed curve instead of just half of it.

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The problem is your “rugbyball”. Looks like you revolved a full ellipse, which produces a double surface. Turn on control points, you will see all are doubled. Try revolving a half-ellipse or using the Ellipsoid command, it should work better.


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As far as I can see Rhino 5.0 (64 bit)

I indeed revolved an ellipse curve.

Will try revolving half a circle, and the ellipsoid-command

Will keep you posted.

Thanks for the tips!

@wim, @Helvetosaur: a “double” ellipse was indeed the problem. It works perfectly now.
Thanks for the suggestions! (and the quick response!)

@Helvetosaur : can you tell me how can I turn on the control points?

Thanks again!

F10 or the icon in the main toolbar that looks like this:


are the control points commands.

In that case you should update to the latest Service Release.