The middle contour line is incomplete in Grasshopper

[Selen]

Hello, I have a problem in creating contour lines on a specific geometry that can be seen on the image below:

The contour command on X direction produces one “planar curve” in the middle, which supposed to be a “closed planar curve”. The open curve doesn’t let me create a boundary surface… I tried other simple breps with the same commands and didn’t have any issues. The problem is specific to this geometry. What can I do to solve this issue?

Many thanks,
Selen

WAFFLE_DOST.gh (38.0 KB)
waffle_dost.3dm (5.0 MB)

(I followed the steps in this tutorial to create a waffle structure: https://www.youtube.com/watch?v=pP09To7o1sA)

[Joseph_Oster]

There is a seam exactly at your contour start point. If your move the start point slightly (one unit in X direction), you get the closed curve you want.

By the way, Area centroid works but it should be Volume centroid. They both produce the same point.

P.S. Your waffle code has other issues but I spent all day on this recently:

Something like this in Grasshopper? (Waffle structure follows curves)

I got something that is close… Enough to see some obvious flaws. The subtle flaws are harder to find. This became intensely complicated Not a beginner project at all. It takes more than a minute after opening the file to see code and geometry. Some notes: I used two clusters. Rib that thickens transverse and lengthwise “ribs” and cBranch that culls the first and last branches of data trees. It has an ‘R’ output that returns the culled branches so they can be merged later. For…

P.P.S. For good measure, you might consider moving the contour start point in both X and Y by half the contour distance? (yellow group)

waffle_2024Oct3b.gh (44.8 KB)

Though I see now that creates a possible problem in the way four pairs of ribs overlap?

In theory there is no difference between theory and practice. In practice there is.
– Yogi Berra

[Joseph_Oster]

Waffle structures are fascinating, here are a couple more:

How can I solve Brep plane data conversion error?

This is the best way to create a waffle structure in my opinion. It fixes a flaw in the original method for creating slots in this thread (which needs a better title!). The fix for that problem is in the white group of this version, which is an extensive rewrite of the original. It creates slots in 2D before extruding the section curves, so no more SDiff. [waffle structure_2024Mar29b] waffle structure_2024Mar29b.gh (228.8 KB) Geometry is internalized, no need for Rhino file. Here is how…

Gradient UV division on waffle script / Bowerbird

Gradient planes is trivial. Extensive work was required, however, to handle the donut shape that generates multiple section curves per plane. I started from this, done two days ago: [waffle structure_2024Mar31b] [waffle structure_2024Mar31b2] P.S. No plugins. P.P.S. I don’t know why there is no GH file for this donut? Here it is: (Oct 3, 2024) waffle structure_2024Mar31b.gh (128.2 KB)

[Selen]

Thank you Joseph_Oster , moving the point in x direction solved the open curve issue. Now I can produce bondary surface without a problem.

Is it possible to know why there was a seam on the curve? To keep the point in exactly at the center, is there a way to fix this issue by removing/joining the seam?

Also thank you for your other tutorial suggestions on waffle structures. After this code, I will try them!

[Joseph_Oster]

@Selen

Is it possible to know why there was a seam on the curve?

It depends on how you created that brep, which is not in the GH code.

P.S. To elaborate slightly…

• The seam is likely a remnant of a sphere or revolved surface used to construct the brep.
• I don’t know precisely why it interferes with Contour.
• I don’t know how to “remove/join” a seam, though it might be possible to move it if I had access to the process that created the brep, which I don’t. Maybe it was created in Rhino?
• There are many things I don’t know or can’t control.

I prefer to work with things I know and can control. In my experience, it is common that nudging geometry slightly avoids problems like this. The brep is nearly 600 units in X and Y. Moving the contour start point as little as 0.01 units in X (maybe less?) avoids the issue so I would do that and move on

There are more important issues to solve in creating a waffle structure.

[Selen]

Yes, I made the geometry by boolean subtraction of 2 spheres. Now I understand how seam is formed.

It makes sense to nudge the geometry when needed, and moving on with simple solutions. Thank you again!