Unrolling baked texture on cone's surface

Rhino Rhino for Windows
1

Hello

I think I have encountered a limitation of Rhino and I am wondering if there is another way around this problem.

I have applied a custom picture-based material to a cone, and then mapped it with planar mapping in plan view, so that the image is project straight down onto the sides of the cone, as well as the bottom. Next, I used ‘bake’ on the cone, and then unrollsrf with the goal of having the sides of the cone and its mapped texture flattened so I can print and cut out and reassemble as a model.

A cone is a developable surface so I expected this to be easy, but as you can see in the attached image, when Rhino unrolls the surface and applies the baked texture, the texture is wildly distorted. If you then look at the baked texture bmp, also attached, I think you can see why this is happening. Rhino tries to bake the texture into a rectangular frame, when in fact the cone’s surface is shaped like a fan when unrolled. So when I unroll the cone surface, Rhino tries to put this rectangular image onto the fan-shaped unrolled surface, and thus it becomes distorted.

What do I do? Is there a workaround? A plugin that does what ‘bake’ does, but without this error? I am about to try to find a different software for the project, but would much rather not.

Rhino file attached.

Thank you so much in advance.

Brian

cone problem brian.3dm (2.6 MB) !
baked cone texture
baked%20cone|500x500 !
cone as seen in plan view
cone%20plan%20view|488x500 !
unrolled cone with texture (distorted)
unrolled%20cone|660x500

2

Hello - I do not think you should need to bake for this - Unrolling should, I think, unroll the texture coordinates.

https://mcneel.myjetbrains.com/youtrack/issue/RH-54622

-Pascal

3

Well that’s certainly odd!
I unroll developable surfaces with image mapping all the time without issue, so I thought I’d do a quick experiment.
I should point out that I use a script that unrolls with UV coords which I’ll attach to this post. (Normal UnrollSrf doesn’t unroll the image coords correctly).

UnrollWithTextCoords.rvb (3.5 KB)

Ok, so I made a cone planar mapped a texture and used UnrollWithTextCoords which normally would work. No joy, the texture was sheared off and distorted.

Next I split the cone into two pieces and then it ran fine. See attached. Note I redrew your cone by eye so the dimensions will be out.

cone problem brian_ST.3dm (371.6 KB)

Hope that helps, Steve

Edit: Note that you want to watch the normal direction of unrolled pieces as sometimes they come in reversed with this script for reasons that escape me.

4

Hey Steve. Thank you for this. I’ll take your file for a spin when I have a moment. I had an inkling that UV mapping was the next step for me in gaining more control over unrolling. Thanks again.

Brian