I used BufferGeometry to merge several mesh together, but I recorded the index for each mesh, and there’s an operation to hide the individual mesh. What should I do or have a better way to handle it?

# How to solve the operation of hiding some mesh after BufferGeometry merges multiple mesh

Providing you have a single group in each geometry for your meshes, with the indices you kept you should:

- offset the indices of mesh #2 by the number of vertices of mesh #1 (meaning, add to each index the vertex count)
- offset the indices of mesh #3 by the number of vertices of mesh #1 + mesh #2
- and so on

Then, if you want to show only mesh #1, then call `.setIndex()`

on the merged mesh with the indices of mesh #1.

If you want to show only mesh #2 + mesh #3, then call `.setIndex()`

with the concatenation of the indices of mesh #2 and mesh #3.

Are there any cases provided? Because I’m not very skilled.

Something like (I didn’t know `setDrawRange`

existed when I replied to use `setIndex`

above):

Say you have `geom1`

, `geom2`

and `geom3`

the `BufferGeometry`

of your three unmerged meshes, and `geom`

is the `BufferGeometry`

of the merged meshes.

To show only mesh 1, use `geom.setDrawRange(0, geom1.getIndex().array.length)`

To show only mesh 2, use `geom.setDrawRange(geom1.getIndex().array.length, geom2.getIndex().array.length)`

To show only mesh 3, use `geom.setDrawRange(geom1.getIndex().array.length + geom2.getIndex().array.length, geom3.getIndex().array.length)`

To show everything again, use `geom.setDrawRange(0, Infinity)`

.

I did not test this, but I think it should work…

All right, I’ll try it first.

This method seems to show only a single mesh, and if I want to display two or more at the same time, it doesn’t seem to work.

Do this a single time:

```
var geoms = [geom1, geom2, geom3];
var indices = [];
var ofst = 0;
geoms.forEach((g) => {
var index = Array.from(g.getIndex());
for (let i = 0; i < index.length; ++i) {
index[i] += ofst;
}
indices.push(index);
ofst += g.getAttribute("position").count;
});
```

Then, to show mesh 1 + 3:

```
var idx = [
...indices[0],
...indices[2]
];
geom.setIndex(idx);
```

To show 1 + 2 + 3:

```
var idx = [
...indices[0],
...indices[1],
...indices[2]
];
geom.setIndex(idx);
```

**Warning: untested code**