**I started with “indexed”.**

With the calculation of the positions and indices for the individual triangles it proceeded fast. A wireframe mesh was present very quickly in the sandbox and the examples of the BufferGeometry.

But there are two problems, uvs and material index:

If not “circular open”, the last Geometry-vertices / BufferGeometry-indices are identical. For the uvs you need at BufferGeometry others! I could fix this by adding extra indexes. However, the uniform structure is already clearly disturbed.

(I wrote: *The second problem is crucial.*

*Because each Geometry-face in THREEf can dynamically have a different material index, the Geometry-faces are constantly manipulated. For indexed BufferGeometry the material index is linked to the indices / positions via groups. The system is then completely mixed!*

*But even more problematic, then get two adjacent triangles with common index an identical material index.* *And this is not possible! ?* )

**UPDATE:**

I now have the definitions of BufferGeometry for cylinders, etc., viewed. Apparently, the groups refer to the indices and not the positions Then it may be with indexed.

I still need to learn a lot about three.js!