メタ:
- id: en/kyutai-insatuvmap
- slug: en/kyutai-insatuvmap
- url: /blog/en/kyutai-insatuvmap/
- title: Splitting a sphere's UV map into printable sections with Blender and 3D-Coat
- date: 2024-06-09T19:42:00+09:00
- tags: Blender, 3DCoat, 3D Models, Textures

> **Note:** This article is more than one year old. Names and default behavior for remeshing, the UV editor, and baking vary between Blender and 3D-Coat versions. The screenshots show the interfaces used at the time.
> - My comment that 3D-Coat has no automatic UV alignment feature reflects my impression at the time. Newer versions, workflows, or plugins may improve this.
> - Check the current URLs and licenses of equirectangular HDRI sources such as Poly Haven.
> - Printing and attaching the texture to a physical object is an experiment; paper, printer, and scale affect the result.

These are my notes on controlling a sphere's UV map for printing.

I wanted to turn the UV map of a perfectly spherical 3D model into a shape that would be easier to manage in print. First, I created a UV sphere in Blender.

![](/blog-assets/media/1e5ffec65501a7010d25d288c863bc3a5bc3706116892d001665631482fd1aa1/2024-06-09-18-51-43-734.webp)
Its faces include triangles and quads. Here is the UV map in that state.
![](/blog-assets/media/ced1b0faf89d0d08ccb810a414fac2ba6f4606d97e472df99c708e2b19c17e23/2024-06-09-18-52-41-231.webp)
It has a jagged edge of triangles. How could I handle that edge when printing it?
![](/blog-assets/media/aba2c1635d119124a8b4e021f63b34d1f41930c4e952d388b108ec67b46c09cf/2024-06-09-18-57-35-264.webp)
I tried remeshing it into quads. At first, it looked promising.
![](/blog-assets/media/a4b1356fde3d9a8b3888469172cf3ccc54336338626a99ed4ec52c275b728092/2024-06-09-19-01-12-312.webp)
Looking at the top, however, the quad mesh did not fill the surface evenly and formed an organic pattern. With this method, I could not fill the round area with uniform quads.
![](/blog-assets/media/5165dae1ed34d276e34c618e6f3510b03cbe9723659e34011c11790098feb24c/2024-06-09-19-01-23-214.webp)
Instead, I wondered whether I could edit the UV map while keeping the mix of triangles and quads. I transferred the UV sphere from Blender to 3D-Coat.

I prepared an equirectangular test image downloaded from HDRI Haven.

![](/blog-assets/media/4d84c8a7dd13657b75eb109b947cc7eccaa986c4a978666059ef29df856a912c/2024-06-09-19-11-12-929.webp)
I applied the equirectangular image to the sphere. The top and bottom edges were jagged.
![](/blog-assets/media/648cf694c6350d92176c003aecd5d5bd1a4a9f607965469c471721ac20b83a59/2024-06-09-19-11-29-024.webp)
From here, I remapped the UVs. I spent hours trying different approaches.
![](/blog-assets/media/1ae4d7db6054e261af1dbb9bb706857f26a4446122225cd51617604bbc88cd13/2024-06-09-11-53-05-129-scaled.webp)
In the end, I manually divided the sphere's UV map into four sections. I struggled because I could not find an automatic way to align the UV map in 3D-Coat. Keeping the scale at 1:1 and the sections horizontal was the key.
![](/blog-assets/media/3f4d246bf8b7179096d121111088431b329a92bf5939937cb4be728c54563f95/2024-06-09-19-15-08-262.webp)
I prepared and applied a texture with degree markings like this.
![](/blog-assets/media/4e21cc7ddac63fc0faacdbb42fc6789e1ef7a2ee1248ca24ec19d8a748cc1018/2024-06-09-19-19-11-298.webp)
I aligned the positions visually, one pixel at a time.
![](/blog-assets/media/0d7ece866d0aeb39db647568de84aba5191a3dcfd51b8fd94d61f73abe2ac982/2024-06-09-19-20-01-725.webp)
Once they lined up reasonably well, I called it finished.
![](/blog-assets/media/2bab4235ba930ecd6c5fd3078bf9b844b255f4e608d565a442617d5a5efb3e16/2024-06-09-19-20-28-119.webp)
I applied the earlier equirectangular image.
![](/blog-assets/media/ae5235f98c17b4b5013b4a3b8da12a66e0efaa1b9ca8c464f237b753951f1395/2024-06-09-19-26-46-252.webp)
Then I printed it. Importing it into Illustrator or a similar program might show UV-map guides, but I have not tested that. If it works, printing would be much easier.
![](/blog-assets/media/9985e17da9f9ce1d4ba475640012f4a94c24397bce70548bf301968642dd045c/2024-06-09-19-27-50-915.webp)
I roughly cut it out with scissors, attached it, and assembled it. Oh! The edges joined up. A happy ending.
![](/blog-assets/media/9c38705d674c39070bcaf99f413d929bed348c495064f5c98a7966d0b6c3682f/20240609_193109.webp)