Is it possible to render an indexBuffer in Three.js by applying uv, normal, and position individually?

Questions
,
1

Current THREE.BufferGeometry

THREE.BufferGeometry
  ㄴ attributes
     ㄴ normal
     ㄴ uv
     ㄴ position
  ㄴ index

1 index : each uv, position, normal

I want to do

(Sudo)
THREE.BufferGeometry
  ㄴ attributes
     ㄴ normal
     ㄴ uv
     ㄴ position
  ㄴ indexBuffer
     ㄴ positionIndex
     ㄴ uvIndex
     ㄴ normalIndex

uvIndex : uv
normalIndex : normal
positionIndex : position

Is it possible to render an indexBuffer in Three.js by applying uv, normal, and position individually?
when export obj, usdz and then import at Blender there’s a seam line and has two vertexes into same point so it can be split like below screenshot

Untitled (18)
Untitled (18)1244×1214 59.8 KB

so I want to get a moving at seam line vertex like this in blender

Untitled (19)
Untitled (19)616×578 178 KB

2

Three.js uses WebGL. Unless there is some new feature that I’m not aware of, WebGL supports indexed drawing via a single index for all attributes (vertex coordinates, colors, texture coordinates, normals etc. ) So, I’d expect that Three.js cannot work with indexed geometry with separate indices for different attributes.

As for the two images and the reason why you need many indices – I’m sorry, I was not able to understand them.

2 Likes
3

Oh… Thanks for reply!
TLDR;
As a side note, I’m currently using a Sphere exported from Three.js’ Obj and USDZ Exporter, and when I imported the Obj and USDZ into Blender, I saw that there were two vertices in the same position on the seam line, so it happened when I moved the vertices in Blender, as shown in the picture.

However, I don’t think Sphere should happen like that. The issue is caused by the fact that 1 index manages uv, position, and normal, and there are 2 uv in the same Vertex position on the Seam line side. (Since there are 2 uv in the same position, the index is also 2 in the current Three.js Exporter.) Therefore, I needed a buffer for each Attribute to remove the duplicate values.

4

You can merge duplicated vertices in Blender (use option “Merge by distance”). After this operation you can move the vertices of the sphere and its surfice will not tear off.

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