Unwrapping Like Paper Sheet

[Frank1000]

Hi,
I wanted to fold open the surface of an object, like if it was a piece of paper. The way that the dimensions of the shape are brought from 3D to 2D, by preserving the shape. Meaning if the skin was of paper and I fold it flat open, the shape wouldn't distort. I need to create the correct 2D shape of the wrap, so I can print a sticker for that unregulated shape, that then fits the object right when applied.

Seems an ICE task to me. Pls share how this could be tackled.



Regards,
Frank

[Helli]

I would do it the other way around. Build your surface and then deform it so you got the final object. Like you would do it in reality

[Bullit]

Is not what bend does?

[Mathaeus]

you can do this, using UV projection. For something like object in picture, procedure could be:
1: apply cylindrical UV prijection, freeze it
2: disconnect edges at UV seams
3: apply un-simulated ICE tree to mesh
4: nodes:
get self.pointlocation > get cls.texture..... UVs (you'll need to navigate down to 'UVs') > convert 2d vector to scalar > convert scalar to 3d vector (one of XYZ components will be without input) > Set Self.PointPosition > root node

You can also check out Deform by UV thread. iamVFX wrote scripts for automatizing - basically 'deform by UV' does reverse of what you want, but it's possible to do 'double reverse', too.
Of course, for anything more complex than cylinder, there is no exact un-wrapping, anymore, there's only a compromise, how strong distortion is acceptable.

[Frank1000]

Hi,
thx for your responses. In my case for using Bend the original object is not a simple enough geometry, it has no clear enough central axis.
Question to Mathaeus, as I understan your approach, its to use the UV texture abilities to deform the mesh. Hope I understand right. Following your process, at point 2., I'm not sure how to disconnect edges at UV seams. I checked the manual and the Texture Editor but didn't find a corresponding function. How is that done ?

Regards,
Frank

[Bullit]

The top view seems to be a perfect circle so unbending the circle shouldn't planify the object?

[Mathaeus]

Hi,

Question to Mathaeus, as I understan your approach, its to use the UV texture abilities to deform the mesh. Hope I understand right. Following your process, at point 2., I'm not sure how to disconnect edges at UV seams. I checked the manual and the Texture Editor but didn't find a corresponding function. How is that done ?

In TE, select>contour Selection. If you have Auto Sync Selection enabled, set to Components, and Edge selection in MCP, it should select UV seams.
Please don't forget, what I mentioned, is a set of main steps. For small adjustments here and there, you're the boss. Anyway it works.

[grahamef]

This is the perfect job for a little bit of trigonometry. Just get the X and Y coordinates of each point (or actually X and Z in this case), use ArcTan 2 to find the corresponding angle, calculate the arclength according to angle times radius, add an offset depending on where you want it to unfold from, and that's your U coordinate -- no need to actually unfold the object.

[Frank1000]

Hi Bullit, yes true. But my final object is not like this test object here, it is not perfectly round.

[Frank1000]

Hi Mathaeus,
the "disconnect edges at UV seams", is that meant as Model>Modify>Poly.Mesh command ?
Regarding "set to Components, and Edge selection in MCP", is that meant on the right side under "Select" ?

I have this so far :

[Frank1000]

Hi Grahamef,
do you mean to do this in ICE ? Like a simulated tree with an animation ?

Regards,
Frank

[Mathaeus]

Hi Mathaeus,
the "disconnect edges at UV seams", is that meant as Model>Modify>Poly.Mesh command ?
Regarding "set to Components, and Edge selection in MCP", is that meant on the right side under "Select" ?

TE in my previous post, means Texture Editor, MCP is Main Command Panel. Anyway you can always set some texture to object, for finding UV seams.

[Frank1000]

Hi Mathaeus,
ok, thx for info. The process you've suggested, at this point of seeing the way the polygons are textured in the TE, do I need to create a curve from selected edges ? Not yet clear to me what the scope is. Basically what is meant with the UV seams and how to disconnect them, respectively what I then would get, so I would know that UV seams have been disconnected.
Pls let me know how to understand this part.

Regards,
Frank

[grahamef]

Hi Grahamef,
do you mean to do this in ICE ? Like a simulated tree with an animation ?

Regards,
Frank

Yes, in ICE but there's no real need for simulation. But if your real object isn't actually round it's a bit trickier.

[Mathaeus]

Hi Mathaeus,
ok, thx for info. The process you've suggested, at this point of seeing the way the polygons are textured in the TE, do I need to create a curve from selected edges ? Not yet clear to me what the scope is. Basically what is meant with the UV seams and how to disconnect them, respectively what I then would get, so I would know that UV seams have been disconnected.
Pls let me know how to understand this part.

Perhaps you could try the procedure, with or without some step. You know, reality says more than thousand words... Anyway, to answer the question, this time:
With any of mentioned methods in this thread, you have to define the cut on your cylinder. When it is cylinder, you see only two borders. Once it's "paper sheet", you see four borders. Disconnecting at UV seam, defines two borders. missing at cylinder.

What "UV seam" means in 3d world, perhaps is best to go with picture again - let's say, by typing these words in Google search.

[Frank1000]

Hi,
UV seams I figure is the edges of the textured areas. I don't get what disconnecting them means and where I actually disconnect them and what then have happened when I have disconnected them and how I see it that it has happened. The process is not yet clear to me what is meant to happen. Sry.