How to find a specfic object in a merged buffergeometry?

For the performance purpose, in my case I mergerd cell shape as one buffergeometry. My question is while I raycaster one of cells and get the following content

distance: 0.5163975193122629
face: t {a: 5434, b: 5433, c: 5440, normal: t, vertexNormals: Array(0), …}
faceIndex: 4738
object: Un {uuid: ‘04E2D3A2-59F6-4CE0-AF94-003A0E9E13DD’, name: ‘rois’, type: ‘Mesh’, parent: e, children: Array(0), …}
point: t {x: 0.16790426007605952, y: 0.3279409435830404, z: 0, isVector3: true}
uv: t {x: 0.16790426007605952, y: 0.3279409435830404, isVector2: true}
[[Prototype]]: Object

Can I use faceIndex to get the exacti one of the cell?

I created a range dictionary by myself like this

roisDictionary.push([roisName, count -[roisName].length,[roisName].length]);

So I can compare whether the faceIndex is in one of the ranges

let faceIndex = genes.raycaster_points.filter(x => x.object.type === 'Mesh')[0].faceIndex;
roisDictionary.forEach(item => {
   if (faceIndex > item[1] && faceIndex < (item[1] + item[2])) {
        mouseHoveredRoisIdx = faceIndex;
         if (!cellName.includes(item[0])) {
             mouseHoveredRoisName = item[0];

I did the implementation like this, but while the mouse hoverd the cell, it is the another cell, seeems this is not the correct way to use faceIndex.

Depending on your exact use-case, I think it’s easier to keep the original (unmerged) set of meshes in a separate group or scene that are not rendered but solely used for ray-testing.

So you render the merged geometries, but keep the original intact for “game logic”.