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# MDLIndexBitDepth

Options for the size of integer data in a submesh’s index buffer, used by the [`indexType`](/documentation/ModelIO/MDLSubmesh/indexType) property.

```
enum MDLIndexBitDepth
```

## Overview

For optimum performance, an index buffer should generally use the smallest data type that fits the number of indices it contains.

## Topics

### Constants

[`MDLIndexBitDepthInvalid`](/documentation/ModelIO/MDLIndexBitDepth/invalid)

The submesh has not been initialized or its data type is unknown.

[`MDLIndexBitDepthUInt8`](/documentation/ModelIO/MDLIndexBitDepth/uInt8-swift.enum.case)

Each index in the submesh’s index buffer is an 8-bit integer.

[`MDLIndexBitDepthUInt16`](/documentation/ModelIO/MDLIndexBitDepth/uInt16-swift.enum.case)

Each index in the submesh’s index buffer is a 16-bit integer.

[`MDLIndexBitDepthUInt32`](/documentation/ModelIO/MDLIndexBitDepth/uInt32-swift.enum.case)

Each index in the submesh’s index buffer is a 32-bit integer.

## Relationships

### Conforms To

[`Hashable`](/documentation/Swift/Hashable)

[`Equatable`](/documentation/Swift/Equatable)

[`SendableMetatype`](/documentation/Swift/SendableMetatype)

[`BitwiseCopyable`](/documentation/Swift/BitwiseCopyable)

[`RawRepresentable`](/documentation/Swift/RawRepresentable)

[`Sendable`](/documentation/Swift/Sendable)

---

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