Does anyone have a suggestion on how to unroll a cylinder to a plane?
Context: 
I have a photogrammetry model of a column with sculpted details that I want to unroll into a flat plane turning it into a frieze. 
Mesh density is too high to do it manually.

Hello keppel  

I can not find any thing close to what you want to do unless it is like rigging the cylinder to create an animation of it unrolling and all other similar finds concern UV mapping with I understand is not what you want. I will keep searching to see if I can find a solution to your question

Appreciate the effort Lobo.  I've done a pretty exhaustive search myself with no success.  

Is there any way you can project the details to a vector displacement map or even a normal map on a much more lower density column like the cylinder in your example, then manually unwrap that?

Yup, what @LuxXeon said is probably the logical way of doing it. Bake/project the high poly to a displacement, apply it to a lower poly mesh, and unroll that mesh.

Without seeing the mesh [how much relief there is in the carving/sculpting], I wouldn't discount pure brute force. Volume/area selection tools, and going in small increments, it'll take you a bit of time but its not difficult, just tedious [you don't have to be perfect, the process is usually somewhat forgiving]. In the days before modern UV unwrapping tools that was sometimes the only way to do it!

Or as @Lobo3433 mentions, you could just rig it. A ring of bones, rotate them until they're straight, and save the transformed mesh.

Thanks for the tips, they have given me some ideas to work with.  I can picture rigging the mesh like a tail could work.  Whilst reading your replies it occurred to me that I might be able to do a series of front ortho renders of the column.  Render, rotate, render, rotate etc, Then take the image sequence and stitch them into one image and use that image to generate, normal and displacement maps for a new mesh.    Thanks again for the help. 

keppel posted at 12:23 AM Sun, 30 July 2023 - #4471479

Whilst reading your replies it occurred to me that I might be able to do a series of front ortho renders of the column.  Render, rotate, render, rotate etc, Then take the image sequence and stitch them into one image and use that image to generate, normal and displacement maps for a new mesh.    Thanks again for the help. 

You're far better off baking a projection from one mesh to another mesh, even if you use a basic 24 sided cylinder, than you would be trying to stitch a series of images together. You wouldn't necessarily even need to "flatten" the cylinder after that. UV map it, which will given you a flattened/"unrolled" image when you bake it. Then create a flat plane, that shares the same UV space/image.

CloudCompare has a tool to unroll a cylinder. Some functions in Cloud Compare will only work on point clouds, I don't recall if this one is limited to point clouds only or if it will work on a mesh

unroll in CloudCompare