Hi
This model is a part of backrest I import from step file. Currently, they contain 5 surfaces, I join into 1 surface. Then I use unfold surface UV. I intend re-model this surface then using Flow along surface in order to wrap it back.
But I only can select a part of surface. detail in photo below:
Your object is a polysurface, not a single surface. FlowAlongSrf only works with a single target surface and a single base surface. It does not work with polysurfaces.
Join when used on surfaces creates a polysurface. It does not merge the surfaces into a single surface. A polysurface is a collection of surfaces “glued” together. Each individual surface retains its own UV parameter system.
Hello - in this case, you can jump through a couple of hoops and get something that works - it might be easy enough to reconstruct that shape as a single surface as a target for FlowAlongSrf and then Pull the results to the existing polysurface.
Or you can merge the surfaces - I’d do this on a copy - of your polysurface.
Explode
ShrinkTrimmedSrfToEdge (the surfaces extend slightly past the trimmed edges.
UntrimAll
ExtendSrf each edge at the top end bottom so they line up exactly
It makes the surfaces messy- that’s why we’re working on a copy. There are locations on the extended surfaces that fall verry slightly away from the neighboring surfaces.