Asking for the Extruding issue

Hello everyone,

I would like to have your help for this issue. The issue is when I extrude a group of lines with the Z axis, the top and bottom line of the extrusion do not match. That means I can see the top line and the bottom line separated (they are supposed to be matched to 1 line when viewing from the top).

If you take a look of my GH file and zoom in many times in the top view, you can see that. Please help me how to fix this issue.

Thank you very much in advance!

I am looking forward to your helps.

Best regards,


02-01-2019 - (28.6 KB)

Could just be grasshoppers display. Did you try turning off bump preview and setting the display to high quality? Also, how does it look when you bake it.

Hi Michael,

Thanks a lot for your reply!

I have already done all of the things you suggested before. It did not work. Cause I was trying to use the Region Difference component to boolean it with another extrusion, but it did not work.

I also tried to do Region Difference with some simple surfaces (extruded from straight lines) and they worked perfectly.

I did bake to Rhino and the boolean failed.

I think the issue starts from Divide Curve component. I still do not understand this :frowning:

Please let me know some more solutions for this!

Many thanks,


I look at your file and didn’t see a problem.
I extracted 2 points on the same position (execept Z ) and get that

You could have problems of tolerances (did you try to change it ?) problem of antialisasing ?
Make a screen capture, or show where an operation fail …

Hi Laurent,

Thank you very much for your reply!

The model I am building is in Meters unit. So following your suggestions, I changed the Absolute tolerance in Rhino to 0.000001 and the Angle tolerance to 0.0001, but I still have the same problem.

I tried to make a simple line and zoomed in. It still has the problem. So I guess Michael is right. It is just the display.

But if you have any suggestions, please let me know!

Thanks a lot, guys! I really appreciate your helps!

Best regards,


As you look at extrusion, you look at mesh and mesh far from origin could have some problems. Vertices are , by default, represented by float and not double. This could lead to some artefact. But the geometry (Nurbs) in Rhino is stored in double.
I asked you to change the tolerance not for the vizualisation but for

Tolerance (bigger or lower, it depends) can help not to have failing boolean.

Oh, I see what you meant now. Thanks a lot, Laurent!

By the way, please kindly help me out with the Boolean issue!

The GH file attached in this reply has 2 components. One is the window of my model. The other one is the bars which I wanted to use them to trim the window (to make the window smaller). I tried several ways in GH but I have not got it.

Thank you very much!


02-01-2019 - Asking (341.3 KB)