VK_EXT_shader_tile_image — fast access to tile data

Some GPUs expose “tile” or “subpass” data paths that let shaders read from on‑chip color/depth without a round trip to memory. VK_EXT_shader_tile_image is a portable way to tap into that.

In this sample we treat it as an optional optimization: the pipeline remains correct without it, and we only take a “fast path” when the device advertises support.

What problem it solves

Post‑lighting texture reads from the just‑written color can be expensive. With tile image access, certain patterns become cheaper and more deterministic on supported hardware.

How we handle it in this sample

  • We enable the feature if present and expose a boolean you can check in code.

  • The renderer still uses clean Synchronization 2 barriers and ends dynamic rendering before formal layout transitions. That keeps the code understandable on devices that don’t support tile reads.

Guidance

Use it as an optimization. Write code that’s correct everywhere, then add tile‑image fast paths when available.

Where to look in the code

  • Feature detection and enablement:

    • renderer_core.cpp

  • Dynamic rendering setup and attachment transitions (kept explicit for clarity):

    • renderer_rendering.cpp

    • renderer_pipelines.cpp

Future work ideas

If you want to demonstrate tile-image usage more directly:

  • Add a small “local read” post effect that reads from the current color attachment and compares with a regular sampled path.

  • Add a device capability print (development-only) so students can see when the fast path is active.

  • Add a micro-benchmark scene and compare bandwidth on tile-based GPUs.

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