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# MTLIndirectAccelerationStructureMotionInstanceDescriptor

A description of an instance in an acceleration structure that the GPU can populate, with motion data for the instance.

```
struct MTLIndirectAccelerationStructureMotionInstanceDescriptor
```

## Overview

This memory layout corresponds to the [`MTLAccelerationStructureInstanceDescriptorType.indirectMotion`](/documentation/Metal/MTLAccelerationStructureInstanceDescriptorType/indirectMotion) instance type.

## Topics

### Specifying the instance

[`accelerationStructureID`](/documentation/Metal/MTLIndirectAccelerationStructureMotionInstanceDescriptor/accelerationStructureID)

The acceleration resource handle to use for this instance.

### Specifying motion data

[`motionStartTime`](/documentation/Metal/MTLIndirectAccelerationStructureMotionInstanceDescriptor/motionStartTime)

The start time of the motion instance.

[`motionStartBorderMode`](/documentation/Metal/MTLIndirectAccelerationStructureMotionInstanceDescriptor/motionStartBorderMode)

The motion border mode describing what happens if Metal samples the acceleration structure before the motion start time.

[`motionEndTime`](/documentation/Metal/MTLIndirectAccelerationStructureMotionInstanceDescriptor/motionEndTime)

The end time of the motion instance.

[`motionEndBorderMode`](/documentation/Metal/MTLIndirectAccelerationStructureMotionInstanceDescriptor/motionEndBorderMode)

The motion border mode describing what happens if Metal samples the acceleration structure after the motion end time.

[`motionTransformsCount`](/documentation/Metal/MTLIndirectAccelerationStructureMotionInstanceDescriptor/motionTransformsCount)

The number of motion transforms belonging to the motion instance.

[`motionTransformsStartIndex`](/documentation/Metal/MTLIndirectAccelerationStructureMotionInstanceDescriptor/motionTransformsStartIndex)

The index of the first set of transforms describing one keyframe of the animation.

### Specifying the user identifier

[`userID`](/documentation/Metal/MTLIndirectAccelerationStructureMotionInstanceDescriptor/userID)

A user-assigned ID to help identify the instance.


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