# Voxel Brush

The voxel brush labeling tool is a 3D pixel-wise tool to assign voxels on NRRDs to certain classes.

{% hint style="info" %}
The Voxel Brush tool is supported across the Medical labeling editor.
{% endhint %}

## Adding a Voxel Brush tool to your project

From your project's *Settings* tab, enter the *Category Schema* section. Click on *Add Category*, then on *Voxel Brush*. The tool will be added to your project:

<figure><img src="https://3895963154-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FTcOUG6rfWxqGM0N4db2P%2Fuploads%2FRbgHkv3eSHMlJCncT2eM%2Fimage.png?alt=media&#x26;token=44c53540-d08b-4a4e-b059-b6b83382e17e" alt=""><figcaption></figcaption></figure>

## Voxel Brush Settings

<figure><img src="https://3895963154-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FTcOUG6rfWxqGM0N4db2P%2Fuploads%2FJCLbqOUpOTeCW5kbRRpT%2Fimage.png?alt=media&#x26;token=e70bea5d-e889-46b6-b64d-5f6200b9cf99" alt=""><figcaption></figcaption></figure>

Once the tool has been added to your project, clicking on it wil reveal its settings.

**Schema ID**: This is a unique ID Ango Hub assigns to your tool. It's most important when attempting to import pre-annotations. [Read more about medical pre-annotations here](https://docs.imerit.net/data/importing-and-exporting-annotations/importing-annotations/importing-nrrd-annotations).

**Title**: A name of your choosing for this tool/class.

**Required**: If enabled, the annotator must have created at least one segmentation with this tool before being able to submit the task.

**Add Classification**: From this section, you may add nested classifications (attributes) to your class. Please refer to [the docs page on the medical labeling editor](https://docs.imerit.net/labeling-editor-interface/medical-labeling-editor#tool-class-list) for more information on how to annotate attributes.