# Diagonal grid...singularity?

Hi, everybody!
I’ve been practicing going with my tutorials from Tedeschi’s book, Algorithm Aided Design.
There’s something I’m trying to wrap my head around. I did a Diagonal Grid example, but, I get a weird shape on a peak in a surface you will see attached.

As you can see, the surface has a big peak, it was made in Rhino moving the control points. In Rhino “points on” the surface to notice that the control points do intersect with other control points, so I’m guessing that’s an issue.
Now notice how the lines at the diagrid looks all messy there, is there a way to fix it?

Despite it being a example of a diagonal grid, I thought I could use this example to make some low poly skins out of nurb surfaces.

Attached you’ll see the rhino file and the gh file.

diaGrid_lowpoly_surf.3dm (8.0 MB) diaGrid_lowpoly_surf.gh (23.9 KB)

shameless bump

The problem is in your surface itself, you can see the difference.

hi @HugoJBaez, Since your surface is based on uneven Control Points as you are modifying the geometry by moving the control points, I would suggest you use more like a Curve Division based approach. Something like this:

I hope this helps: CRV_diaGrid_lowpoly_surf.gh (14.2 KB)

Its definitely a bit different approach than Arturo’s tutorials that you are following, but since you’re surface geometry is not even topology(Control Polygon) you would need to approach the problem a little differently.

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Ok, I just saw your video and I think I get the logic.

Yes, the book works with an even control point surface, like you said. And honestly I was not expecting a freeform surface to change a lot. But it seems like it does.