A deep dive into keeping a Metal-rendered canvas responsive during pan, zoom, and rotation gestures on iOS. The technique involves reprojecting the most recently GPU-rendered frame using transform matrix inversion and concatenation while a new offscreen render is in progress. Key implementation details include using CAMetalLayer with presentsWithTransaction enabled, coordinating layer updates inside CATransaction blocks, rendering with an overdraw margin to hide edge artifacts, and dynamically disabling MSAA during active gestures to reduce GPU workload and improve responsiveness.
Table of contents
# Reprojecting the existing frame# Requesting and handeling new rendered state# Rendering beyond the viewportCoordinating layer updates with CATransaction# Disabling MSAA during active gestures365 Impressions