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# voxelIndexExtent

The indexes that define the corners of the three-dimensional voxel grid.

```
var voxelIndexExtent: MDLVoxelIndexExtent { get }
```

## Discussion

This property determines which [`MDLVoxelIndex`](/documentation/ModelIO/MDLVoxelIndex) values are valid for referring to the contents of the voxel array using methods such as [`setVoxelAtIndex(_:)`](/documentation/ModelIO/MDLVoxelArray/setVoxelAtIndex(_:)) or [`voxelBoundingBox(atIndex:)`](/documentation/ModelIO/MDLVoxelArray/voxelBoundingBox(atIndex:)). For example, if the minimum extent is `{0, 0, 0, 0}` and the maximum extent is `{10, 10, 10, 0}`, the voxel index `{5, 5, 5, 0}` lies within the array but the voxel index `{0, 20, 10, 0}` does not.

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