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Tune tile priority functions

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Tom Payne
2013-03-26 20:38:34 +01:00
parent 5e8b0de66d
commit 1d22d2fdde
2 changed files with 10 additions and 5 deletions
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12
src/ol/map.js
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@@ -500,12 +500,16 @@ ol.Map.prototype.getTilePriority =
if (!frameState.wantedTiles[tileSourceKey][coordKey]) {
return ol.structs.PriorityQueue.DROP;
}
// Prioritize tiles closest to the focus. The + 1 helps to prioritize tiles
// at higher zoom levels over tiles at lower zoom levels, even if the tile's
// center is close to the focus.
// Prioritize the highest zoom level tiles closest to the focus.
// Tiles at higher zoom levels are prioritized using Math.log(tileResolution).
// Within a zoom level, tiles are prioritized by the distance in pixels
// between the center of the tile and the focus. The factor of 65536 means
// that the prioritization should behave as desired for tiles up to
// 65536 * Math.log(2) = 45426 pixels from the focus.
var deltaX = tileCenter.x - frameState.focus.x;
var deltaY = tileCenter.y - frameState.focus.y;
return tileResolution * (deltaX * deltaX + deltaY * deltaY + 1);
return 65536 * Math.log(tileResolution) +
Math.sqrt(deltaX * deltaX + deltaY * deltaY) / tileResolution;
};