# Intersection analysis with closed curves

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I want to find the intersections between in a set of closed polygons.

Error message if confusing and unhelpful:

Quote

Warning

A triangle and curve mesh is required on the input for correct attribute output.

Can you tell me what this means, and how to find the intersections between closed polygons ?

Edited by AntoineSfx

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Intersection Analysis wants triangulated input geo. So the warning will go away if you use a divide node to triangulate your input meshes. This will output points along the intersection seam. Alternatively, you can use the Boolean node set to Seam and it will output the AB seams from your overlapping input geometry as polygon curves.

Edited by bhouse

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8 minutes ago, bhouse said:

Intersection Analysis wants triangulated input geo. So the warning will go away if you use a divide node to triangulate your input meshes. This will output points along the intersection seam. Alternatively, you can use the Boolean node set to Seam and it will output the AB seams from your overlapping input geometry as polygon curves.

I can't get intersection analysys to work with two triangulated meshes.

It kinda works if input1 is an open curve and input2 si triangulated, but then I have intersection with the interior triangles, which is not what I wanted.

I'm looking for a curve / curve intersection anyway.

Boolean Seam also doesn't really give me the result. The intersection points are there, but they are part of the intersection surface between the two polygons.

The closest I have to a solution is this:

circle1: polygon / open arc

circle2: polygon / open arc

then, input those to intersection analysis.

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Okay. I think I misunderstood what you were asking. Adding a convertline node before the intersectionalaysis should give you the same results as feeding it open curves like so:

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23 minutes ago, bhouse said:

Okay. I think I misunderstood what you were asking. Adding a convertline node before the intersectionalaysis should give you the same results as feeding it open curves like so:

Thanks, that makes sense.

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