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fix(map): unflip avatar overlay Y math #66

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fix(map): unflip avatar overlay Y math #66

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14 changes: 9 additions & 5 deletions src/components/discover/SemanticMap.tsx
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Original file line number Diff line number Diff line change
Expand Up @@ -122,10 +122,14 @@ export function SemanticMap({
setViewState({ target: [bounds.cx, bounds.cy, 0], zoom: bounds.zoom });
}, [viewState, size, points.length, bounds.cx, bounds.cy, bounds.zoom]);

// Project each visible point's world coords to canvas pixel coords using
// OrthographicView's simple projection: pixelsPerWorldUnit = 2^zoom, and
// y is flipped vs world y. Matches deck.gl's internal projection so the
// HTML overlay stays aligned with the ScatterplotLayer rings underneath.
// Project each visible point's world coords to canvas pixel coords.
// OrthographicView defaults to `flipY: true`, meaning positive world Y points
// *down* in screen space (screen convention) — so both X and Y use `+`. A
// previous version had `-` on the Y term, which mirrored avatars vertically
// relative to the ScatterplotLayer rings underneath.
// ppu = pixelsPerWorldUnit = 2^zoom
// screen_x = canvas_w/2 + (world_x - target_x) * ppu
// screen_y = canvas_h/2 + (world_y - target_y) * ppu
const screenPositions = useMemo(() => {
if (!size || !viewState) return [] as Array<{ p: SemanticMapPoint; sx: number; sy: number; px: number }>;
const ppu = Math.pow(2, viewState.zoom);
Expand All @@ -134,7 +138,7 @@ export function SemanticMap({
return visible.map((p) => ({
p,
sx: size.width / 2 + (p.x - cx) * ppu,
sy: size.height / 2 - (p.y - cy) * ppu,
sy: size.height / 2 + (p.y - cy) * ppu,
px: avatarSizeFor(p.confidence),
}));
}, [visible, viewState, size]);
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