Issue with BREP/PLANE intersections

Hello everyone :slightly_smiling_face:
I have some unwanted curves when I intersect a geometry ( lofted sine curves) with planes made by perpendicular frames baseed on the bottom curve of the lofted surface.
I think I am doing it the wrong way : should I evaluate the lofted surface instead?
Also I would like to extrude rectangle along the output line (louvers) instead of the pipe and I can’t work it out…
Thank you for any help.

louvers from surface.3dm (1.1 MB)

louvers from (22.6 KB)


so planes are infinite in space
what happened was that the planes within my blue annotation is cutting the other wing. and vice versa the longer wing’s planes are cutting the shorter one’s.
off the top of my head you can split that loft into two halves and do the intersection separately

You could also switch to Brep|Brep intersections and create planes (or ‘planar surfaces’) that are finite in extent.

Hi David,

I have run into this issue before, where each rectangular brep representing the plane needed different dimensions… I wonder if there isnt a way to extract the “first” plane intersection, like a list item or so, I believe other components such as trim with regions organizes the tree so that item 0 is always the first piece of the trimmed curve and so on.

This could be one way.

louvers from (26.1 KB)

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But what is the ‘first’ piece when you intersect a shape with an infinite plane?

I think you’ll have to filter the list yourself. For example by sorting all the curves by distance to your point of interest, then extracting the first item from that list.

Edit: ah, I think that’s pretty much what @HS_Kim did.