Metal 2 on A11 — Imageblocks

Tech Talks

Imageblocks

• 2D data structure accessible from shaders
  - Single pixel access from fragment functions
  - Full access from kernel functions
• Multi-plane layout
  - Efficient bulk storage of pixels to textures
• Supports optional format conversion

Accelerated Image Movement

Imageblocks in Compute Kernels

• Dimensions are defined via API
• MTLComputeCommandEncoder.setImageBlockWidth(_:height:)
• Pixel structure defined in shading language
• Accessed using an imageblock<T> argument

Storing Imageblock Slices to Textures

• Adjacent subsets of imageblock planes are called slices
• Slices of up to 4 components can e stored together

Imageblocks in Fragment Functions

• Dimensions are defined via render pass API
  - MTLRenderPassDescription.titleWidth
  - MTLRenderPassDescription.titleHeight
• 2 ways to declare pixel structure
  - Define it in the function (explicit)
  - Use render pass attachments (implicit)

Implicit Imageblock

Improved space efficiency

Choosing Between Implicit and Explicit Imageblocks

• Implicit
  - Function must support multiple texture pixel formats
  - Convenience of load and store actions
• Explicit
  - Define complex per-pixel data types
  - Transient usage within a render pass

Mixing Implicit and Explicit Imageblocks

• Choose the right tool for the job !
• Supports incremental adoption
• In shading language, supply 2 imageblock arguments

New Packed Data Types

• New shading language types match API pixel formats
• Accelerated conversion to / from floating point
• Describe packed layouts everywhere
  - Explicit imageblocks
  - Vertex attributes
  - Uniforms

GPU Debugger Support