Joining two surfaces, with different materials assigned to them

Hi all,

I have a question regarding the joining of surfaces. I want to join two sheets together. 1 has a transparent material assigned and the other white reflective. When I join these however the transparent material is the only one left.

I would like to join these surfaces and bend them together using point control. But it is important that they retain their own properties, which they lose with join or boolean union. If I don’t join them they will have different control points and, when bent, move slightly apart. Which is also not what I need.

Curious to hear your suggestions!


To edit the “joined” surfaces as one entity using control points you will need to merge the surfaces into a single surface. MergeSrf merges surfaces.

You could edit a single surface into the shape you want. Then split the surface into two surfaces and assign different materials to each.

Hi Morgan - is it critical that the surfaces retain their materials during point editing, or can these be assigned once the shape is as you like it?


Hi Pascal, no they do not need to retain properties during editing.

Hi David, I did indeed try to do that but at the moment it still says my edges are too far apart.

Hi Morgan - can you post the two surfaces?


@Morgan_Ruben What did you try?

Hi Pascal, Sorry for my late reply. I have been really busy these past days. Please find the file attached.

dual surface.3dm (66.6 KB)

Hi David,

Thanks for the response. And sorry for not responding sooner, these past days have been a bit hectic.
I have uploaded a tryout file so that you can get a better grasp of my problem.

Hi Morgan - the surfaces appear to be identical except the smaller one is a shrunken version of the outer one. A couple of possibilities-

.DupBorder the inner surface. Hide or delete the surface.
UntrimAll the outer surface.
Split the surface with the border curve.
The result will be two identical surfaces with control points in the same locations - you can edit them together by making sure you select points from both at the same time, or match up the point locations afterwards.


Untrim the outer surface as above but don’t split the surface until the shape is right. Use OffsetCrvOnSrf by .25 to create the splitting curves from the surface edges, or ExtractIsocurve may work well in this case.


Hi Pascal, Thanks! I will try your suggestions.