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# Model I/O Data Types

## Topics

### Data Types

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

The minimal volume containing an object, used by the [`boundingBox(atTime:)`](/documentation/ModelIO/MDLObject/boundingBox(atTime:)) method.

[`typealias MDLVoxelIndex`](/documentation/ModelIO/MDLVoxelIndex)

A 4-component vector encoding the location of a voxel in a voxel array and describing its relation to an object’s volume.


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