---
title: "replaceMutableTransforms(_:)"
framework: realitykit
role: symbol
role_heading: Instance Method
path: "realitykit/lowlevelinstancedata/replacemutabletransforms(_:)"
---

# replaceMutableTransforms(_:)

Replaces the per instance transform data synchronously on the CPU.

## Declaration

```swift
final func replaceMutableTransforms(_ callback: (UnsafeMutableBufferPointer<float4x4>) -> Void)
```

## Discussion

Discussion The transform buffer’s contents are unspecified, and it is the caller’s responsibility to populate the buffer with valid data. The transform buffer provided is only valid for the lifetime of the callback.