Grasshopper fails to get surface normal

[Yiming_C]

Hello friends, can you please help me with this simple file? I am trying to use the evaluate surface to get a surface normal, but it wont let me. Any help is appreciated, thank you!

SURFACE.gh (4.1 KB)

SURFACE.3dm (114.2 KB)

[martinsiegrist]

You need to find the closest point first

SURFACE_cp.gh (6.7 KB)

[ferry59]

Works just as well.

[Tom_P]

please check martin s post as solution.

[martinsiegrist]

Yes this works when the surface is untrimmed

[Yiming_C]

Thanks bud!

[Yiming_C]

Thank you!