Surface Blend Problem

Rhino
,
1

Hi guys, I’m new to Rhino and currently working my way through video tutorials. I’m currently modeling the knife from the latest video but i got stuck with surface blend.
In the video when Kyle applies the BlendSrf (https://youtu.be/8Yv2Yt88LlU?si=qUcrqV_C7kQ4b1Nw&t=1125), he get’s just 7 lines which he can easily edit. When i apply it, I get a ton of lines which results in way to many points. Also, my Interior shapes is greyed out for some reason.
What am I making wrong?

EDIT:
Added the .3dm file. Interior shapes is now clickable but still getting these many lines.

knife_training-V2.3dm (2.9 MB)

Screenshot 2025-09-13 at 16.13.33 (2)
Screenshot 2025-09-13 at 16.13.33 (2)1920×1080 107 KB

Screenshot 2025-09-13 at 16.12.37 (2)
Screenshot 2025-09-13 at 16.12.37 (2)1920×1080 118 KB

2

upload your 3dm file please.
just drag and drop it to the edit window.

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3

i can repeat your dense surface

still digging…
if you move up the top surface - you get the expected result

image
image1501×1152 76.3 KB

EDIT:
sorry i am not able to find a mistake.

workaround:

move the upper surface 2 mm up,
do the blendSrf,
turn on control points (CVs)
move the upper part and the corresponding CVs 2 mm down…

wait for @theoutside or somebody else to tell us what is wrong here

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4

This may be the same problem. If so there is a bug.

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5

Thanks David, yep, thats exactly the same!

Still struggeling with all the terminology Rhino uses, so looks like I did not find this post while searching for the problem :grinning_face:

6

the problem is there is a bug when the surfaces share a coincident edge.

this is fixed in 8.24

weird workaround seems to be if you use odd numbers of cv’s in the surfaces that get blended it works…even numbers do not…

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