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# Model I/O Structures

## Topics

### Structures

[`struct MDLVoxelIndexExtent`](/documentation/ModelIO/MDLVoxelIndexExtent)

The corner voxel indices defining a solid rectangular volume of voxels. Used by the [`voxelIndexExtent`](/documentation/ModelIO/MDLVoxelArray/voxelIndexExtent) property and [`voxels(within:)`](/documentation/ModelIO/MDLVoxelArray/voxels(within:)) method.


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