# What does the "U V W" in surface morph mean? And how can I set them?

I want to use the surface morph of GH, however, the U V W is really confusing me. What does it mean? How can I set this (domain)?

Thanks for any help and suggestions!

They are domains of the surface. U is like X direction of surface, V is like Y direction of surface, W is like Z direction of surface (normal direction thickness). UVW are common nomenclature for surface space (non-2d / non-linear) directions. If you reparameterize your surfaces then these domains will be between 0 and 1.

Thank you, Michael!
I tried you suggestion and reparameterized source and target surfaces, and set UVW as 0-1, however, the results are terrible.
If I use the similar rhino command â€śflow along surfaceâ€ť, it works well.
I made any mistake in GH?

Without a file itâ€™s impossible to tell.

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Check this out for future help: How to ask effective questions

Hi Michael and David,

As you see, the morphed shape is too bad.
morphing.3dm (619.4 KB)
morph.gh (3.6 KB)

Surface Morph needs â€śReference Boxâ€ť as a â€śSource Domainâ€ť, not a Base Surface. Read the input popup tooltip carefully.
Furthermore, your base & target surfaces are both â€śTrimmed Surfaceâ€ť which arenâ€™t the case for both input surfaces. You should prepare single "Untrimmed Surface"for both surface inputs.
So, for this case, try to use Sporph instead of Surface Morph.
https://docs.mcneel.com/rhino/6/help/en-us/index.htm#seealso/sak_splittrim.htm?Highlight=Split%20and%20trim
https://docs.mcneel.com/rhino/6/help/en-us/index.htm#commands/trim.htm?Highlight=trim

morph_re.gh (650.9 KB)
And this also works.

morph_reV2.gh (1.3 MB)

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Thanks, Kim!!

Hi Kim,

Today I carefully studied your two codes. Thank you so much again for your kindness. I learned a lot from your code (especially how to reconstruct an untrimmed surface from a trimmed surface.)

There is one questions I still need your help.
For the UVW setting P0 and P1, why you chose {0.5,0.5,0}?I tried to change it as {1,1,0}, but the results seem to be the same. Actually, I am still confused on the UVWâ€¦

The location you choose is the base point of U & V mapping and defines the U & V and normal directions.
Since I reparameterized the base and target surface and I already adjust the both surfaceâ€™s U & V directions identically, so if you choose whatever location in between 0~1, the result will be the same.
Not exactly the same command, but the Rhino UDT toolâ€™s FlowAlongSrf orSplopworks on a similar principle. Refer if necessary.

I got it, Kim. Thank you for your detailed explanation!