---
title: "replaceVertices(at:commandBuffer:)"
framework: realitykit
role: symbol
role_heading: Instance Method
path: "realitykit/lowlevelmeshresource/replacevertices(at:commandbuffer:)"
---

# replaceVertices(at:commandBuffer:)

Retrieves a Metal vertex buffer for GPU replacement. The buffer’s contents are in an uninitialized state. The renderer waits for the command buffer to complete before using the buffer for rendering.

## Declaration

```swift
final func replaceVertices(at index: Int, commandBuffer: (any MTLCommandBuffer)?) -> any MTLBuffer
```

## Parameters

- `index`: The vertex buffer index to replace.
- `commandBuffer`: The command buffer writing to this buffer, or nil to skip synchronization.

## Return Value

Return Value A MTLBuffer ready for GPU write operations.

## See Also

### Accessing vertex data

- [readVertices(at:_:)](realitykit/lowlevelmeshresource/readvertices(at:_:).md)
- [updateVertices(at:_:)](realitykit/lowlevelmeshresource/updatevertices(at:_:).md)
- [replaceVertices(at:_:)](realitykit/lowlevelmeshresource/replacevertices(at:_:).md)
- [readVertices(at:commandBuffer:)](realitykit/lowlevelmeshresource/readvertices(at:commandbuffer:).md)