Cylinder sub meshes

[royibernthal]

I'd like to have different textures on different sides of a cylinder, as depicted in this image:

A cylinder has 3 faces to the best of my understanding, so with faceUV, I'm only able to divide it into top, middle and bottom. Even if it was possible for me to have "4" faces, I'd need at least the middle to divide into 2 textures from different sources that are not part of a texture atlas, which means faceUV would most likely not be a good solution for this anyway.

https://www.babylonjs-playground.com/#CWPN2T#6

When trying to apply a multimaterial to submeshes, it seems I'm unable to capture the required indices in order to assign each different submaterial to each different face, not to mention dividing the middle face into 2 as well.

 

Any ideas?

[JCPalmer]

First, sub-meshes must be contiguous.  I would check the source for BABYLON.MeshBuilder.CreateCylinder.  If vertices are not ordered the way you need game over.  On the flip side, if you write your own, based on MeshBuilder, then you will know where to make your sub-meshes.

[JCPalmer]

Oh, this is really worse than just that.  This is not possible outside of some-kind of texture atlas implemented in the fragment shader.  Reason is at the borders, you need one duplicate vertices, one for each textures / materials meeting.

When an exporter (Blender / 3DSMax) make multi-materials, not only do they sort vertices to be continuous, but write duplicates.  The real answer is to use an exporter.  Blender can easily make cylinders, & mult-imaterials.  I am not going to teach people how to use it.  Any dev should have a basic understand of at least one exporting app, for just this reason.  It is child's play for them.

[royibernthal]

48 minutes ago, JCPalmer said:

Reason is at the borders, you need one duplicate vertices, one for each textures / materials meeting.

Does that part refer to the issue of dividing the middle part into 2?

 

What if we merge 3 and 4 and have only top, middle (undivided) and bottom, would I still need an exporter?

[JCPalmer]

You would have to look at how the top and bottom are made.  Are they re-using vertices from the side.  If so then no.  You would also need to check that top, bottom, and center are contiguous.  You could still not need to use an exporter, if you copied / edited the CreateCylinder code to get valid results. 

If the middle is contiguous, you might also just make 3 meshes.  It is the same number of draw calls.