❗ Update: Good news! This issue has been fixed in MacOS Version 13.0 Beta 5 (22A5321d) / XCode Version 14.0 Beta 5 (14A5294e)

This command line project reproduces a data error when loading multiple textures with a single MTLIOCommandBuffer.

This is associated to FB10582329 (Apple Feedback Assistant).

Background

The WWDC 2022 session Load resources faster with Metal 3 outlines how to load textures with the new Metal 3 features with MTLIO.

Here are the session's (7:22) directions on loading textures:

// Create Metal IO Command Buffer

let ioCommandBuffer = ioCommandQueue.makeCommandBuffer()

// Encode load commands
// Encode load texture and load buffer commands
ioCommandBuffer.load(texture, slice: 0, level: 0, size: size,
                     sourceBytesPerRow:bytesPerRow, sourceBytesPerImage: bytesPerImage,
                     destinationOrigin: destOrigin,
                     sourceHandle: fileHandle, sourceHandleOffset: 0)
ioCommandBuffer.load(buffer, offset: 0, size: size,
                     sourceHandle: fileHandle, sourceHandleOffset: 0)


// Commit command buffer for execution
ioCommandBuffer.commit()

Here are the session's (15:00) directions for getting a file handle to a compressed file:

// Create an Metal File IO Handle

// Create handle to a compressed file
var compressedFileIOHandle : MTLIOFileHandle!
do {
    try compressedFileHandle = device.makeIOHandle(url: compressedFilePath, compressionMethod: MTLIOCompressionMethod.zlib)
} catch {
    print(error)
}

Reproduction Overview

Running this project...

Displays XCode environment/version and MacOS version information:

# Runs the following shell commands
xcrun --show-sdk-path
xcrun xcodebuild -version
sw_vers

Setup - Load PNG images for each cube face.
Setup - Write the raw bytes (RGBA) using MTLIO Compression Context, using the lz4 compression method.
Load each cube face into cube texture using MTLIO
- If let USE_SINGLE_COMMAND_BUFFER = true (reproduces the data error)
  - A single MTLIO IO Command Buffer is used load all 6 faces (slices) into the cube texture
- Otherwise, create/use 6 MTLIO IO Command Buffers, each loading a single face (slice) into the cube texture.
Verify - Load the bytes of each face (slice) of the cube texture and verify they match exactly originating source bytes.

Observations

Consistently, the last (6th) face is incorrect.
There is no indication of failure
- MTLIO Command Buffer status is complete
```
assert(command_buffer.status == .complete)
```
- Even with Diagnostics / Metal / API Validation, no error nor warning is logged.

Just looking at the first pixel's bytes (4 bytes), looks like the alpha channel is mixed up:

Expected first pixel's bytes: [254, 254, 254, 255]
                                              ^^^
  Actual first pixel's bytes: [255, 254, 254, 254]
                               ^^^

No data errors when using multiple MTLIO Command Buffers (let USE_SINGLE_COMMAND_BUFFER = false).

Example Output (Single Command Buffer)

Generated from a MacBook Pro 2021 M1 Max

-----------
Environment
-----------


Command: xcrun --show-sdk-path
Result: /Applications/Xcode-beta.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk


Command: xcrun xcodebuild -version
Result: Xcode 14.0
Build version 14A5270f


Command: sw_vers
Result: ProductName:		macOS
ProductVersion:		13.0
BuildVersion:		22A5295h


----------------------------------------------------------------------------------------------------
Setup: Load PNG images for each cube face and Write raw bytes (RGBA) using MTLIO Compression Context
----------------------------------------------------------------------------------------------------

2022-07-07 18:03:23.916224-0500 x-mtlio-load-multiple-textures[35986:426065] Metal GPU Frame Capture Enabled
2022-07-07 18:03:23.916607-0500 x-mtlio-load-multiple-textures[35986:426065] Metal API Validation Enabled
Reading raw pixel bytes from PNG texture /Users/pwong/projects/x-mtlio-load-multiple-textures/x-mtlio-load-multiple-textures/cubemap-textures//cubemap_posx.png
Writing compressed cube face (0) texture bytes to /var/folders/bd/9qd81pgj4xj01bg4sgp43dvr0000gn/T/9706F1D2-F318-4A81-9E83-BB722C72F62D/0.lz w/chunk size 65536...
... write completed.
Reading raw pixel bytes from PNG texture /Users/pwong/projects/x-mtlio-load-multiple-textures/x-mtlio-load-multiple-textures/cubemap-textures//cubemap_negx.png
Writing compressed cube face (1) texture bytes to /var/folders/bd/9qd81pgj4xj01bg4sgp43dvr0000gn/T/9706F1D2-F318-4A81-9E83-BB722C72F62D/1.lz w/chunk size 65536...
... write completed.
Reading raw pixel bytes from PNG texture /Users/pwong/projects/x-mtlio-load-multiple-textures/x-mtlio-load-multiple-textures/cubemap-textures//cubemap_posy.png
Writing compressed cube face (2) texture bytes to /var/folders/bd/9qd81pgj4xj01bg4sgp43dvr0000gn/T/9706F1D2-F318-4A81-9E83-BB722C72F62D/2.lz w/chunk size 65536...
... write completed.
Reading raw pixel bytes from PNG texture /Users/pwong/projects/x-mtlio-load-multiple-textures/x-mtlio-load-multiple-textures/cubemap-textures//cubemap_negy.png
Writing compressed cube face (3) texture bytes to /var/folders/bd/9qd81pgj4xj01bg4sgp43dvr0000gn/T/9706F1D2-F318-4A81-9E83-BB722C72F62D/3.lz w/chunk size 65536...
... write completed.
Reading raw pixel bytes from PNG texture /Users/pwong/projects/x-mtlio-load-multiple-textures/x-mtlio-load-multiple-textures/cubemap-textures//cubemap_posz.png
Writing compressed cube face (4) texture bytes to /var/folders/bd/9qd81pgj4xj01bg4sgp43dvr0000gn/T/9706F1D2-F318-4A81-9E83-BB722C72F62D/4.lz w/chunk size 65536...
... write completed.
Reading raw pixel bytes from PNG texture /Users/pwong/projects/x-mtlio-load-multiple-textures/x-mtlio-load-multiple-textures/cubemap-textures//cubemap_negz.png
Writing compressed cube face (5) texture bytes to /var/folders/bd/9qd81pgj4xj01bg4sgp43dvr0000gn/T/9706F1D2-F318-4A81-9E83-BB722C72F62D/5.lz w/chunk size 65536...
... write completed.

-------------------------------------------------
Load each cube face into cube texture using MTLIO
-------------------------------------------------

Using a single command buffer...
... loading completed.

------------------------------------------------
Verify the each face (slice) of the cube texture
------------------------------------------------

Verifying bytes loaded by MTLIO into cube face 0 texture matches original source bytes
Verifying bytes loaded by MTLIO into cube face 1 texture matches original source bytes
Verifying bytes loaded by MTLIO into cube face 2 texture matches original source bytes
Verifying bytes loaded by MTLIO into cube face 3 texture matches original source bytes
Verifying bytes loaded by MTLIO into cube face 4 texture matches original source bytes
Verifying bytes loaded by MTLIO into cube face 5 texture matches original source bytes
Expected first pixel's bytes: [254, 254, 254, 255]
  Actual first pixel's bytes: [255, 254, 254, 254]
x_mtlio_load_multiple_textures/main.swift:201: Assertion failed: Loaded cube face 5 texture does not match original source bytes

peterwmwong / x-mtlio-load-multiple-textures

Background

Reproduction Overview

Observations

Example Output (Single Command Buffer)

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