# Geometry does not intersect

Hi,

Does anyone knows why the first planes do not intersect the polysurface, while they evidently do?

I’m testing at the RAC Sample.

teste_SuavizaToposurface_r1.dyn (70.6 KB)

a plane is an abstract element like vector, you need a geometry to intersect…

You’re not using any lacing or list levels, so the geometry is being compared one to one. It’s comparing the geometry of `List1[n]` with the geometry of `List2[n]`. If your lists aren’t structured to be a direct comparison then you likely won’t get what you’re after. Try adjusting the lacing to cross-product.

Makes sense, but then why are dozen other planes intersecting the polysurface?

Same result.

I even tried to test putting the planes at the Y axis, and got the same result. Just a few planes at the top of the list do not intersect the polysurface.

Ah. The error you’re getting is very important. It’s having a hard time with the geometry. Make sure your planes are larger than the scope of your geometry and don’t have any shared edges. You may also have to simplify your polysurface geometry.

Make sure your planes are larger than the scope of your geometry and don’t have any shared edges.

Aren’t planes abstract geometry that extents to infinity along two axis? I’m confused

1 Like

Yup, sorry, you’re correct. I was still thinking surfaces. That error often comes up with complex or overlapping geometry.

I’d start by trying to isolate the geometry that’s causing problems. Like I said, you may have to simplify or at least explode the geometry at some point.

1 Like

The geometry is intersecting, but the resulting intersection cannot be calculated as a surface due to the complexity of the incoming polysurface. A sad state which results from intersecting significantly complexity areas like this. Effectively Dynamo knows it should get a curve from intersecting a surface element with a plane, but the resulting shape becomes branching or otherwise incorrect for a curve.

As an alternative you may want to try getting a grid of points of the toposurface, using those to generate a nurbs surface, and drawing isocurves on the axis.

1 Like