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GPU picking

Model​

The renderer can allocate an offscreen RGBA8 target, draw points with packed feature ids as color, and copyTextureToBuffer (or readback path) for a single pixel. Decoding uses decodeFeatureIdFromRgba8Bytes.

Coordinates​

Always pass backing-store pixel coordinates ([0, canvas.width) × [0, canvas.height)) aligned with the WebGPU render target.

Composition with FeatureStore​

PointHitTester wraps:

renderer.pickFeatureIdAtCanvasPixel(x, y) → featureId → FeatureStore.getById

Performance​

Picking is O(1) per query relative to vertex count (one render + one readback), but has fixed overhead — avoid calling it every frame for hover unless throttled. Tune pick diameter / framebuffer size to balance precision vs cost.

Live demo​

GPU picking demo — hosted iframe: click the map, inspect FeatureStore properties, watch the highlight style.

API​