| bufferStartIndex | The index of an element where the write operation begins. |
| count | Maximum number of elements which will be written |
NativeArray<T> A NativeArray of size count
Begins a write operation to the buffer
Use this to begin a write operation on the buffer. Using this method results in fewer memory copies than using GraphicsBuffer.SetData, and is therefore faster. For compatibility reasons, you can only call this method on buffers where the buffer has been created with the GraphicsBuffer.UsageFlag.LockBufferForWrite flag set. Unity will throw an exception if called on a buffer where this flag was not passed on creation.
The returned native array points directly to GPU memory if possible. If it is not possible to write directly to GPU memory, the returned native array points to a temporary buffer in CPU memory. Whether it is possible to write directly to GPU memory depends on many factors, including buffer usage, active graphics device, and hardware support.
Because of this, the contents of the returned array are undefined. They may reflect data on the GPU, but no guarantees are made. You may therefore use the returned array only for writing to, not reading from, the GPU.
When you have written to the array, call GraphicsBuffer.UnlockBufferAfterWrite to complete the operation and mark the returned NativeArray as unusable.
The performance of this method will vary depending on whether it can write directly to GPU memory or not, but it will always result in fewer memory copies than using SetData.
The data written to the returned native array must follow the data layout rules of the graphics API in use. See [[Compute Shaders]] for cross-platform compatibility information. Linear writes and no reads are recommended since the buffer might point to write combined memory.
Additional resources: GraphicsBuffer.SetData, GraphicsBuffer.UnlockBufferAfterWrite