Improve webgl coordinate precision. #1005
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For line, point, polygon, and contour features, this uses a localized origin for the view matrix to reduce jitter at high zoom levels. Using global coordinates runs into the limitations of float precision, which manes that small movements are functionally rounded by that precision. When panning at high zoom levels this manifests as jitter where the features jump between discrete locations instead of panning smoothly. The default is to use the first coordinate of the data of the feature for the origin. For features that span a large area, this will not help the jitter far from that coordinate (but won't be any worse that before this PR). The origin function is exposed on the style object, so if a large area feature is needed, the application can bind geo.event.pan to recompute the origin upon significant changes in the map center at high zoom values. Resolves #831.
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For line, point, polygon, and contour features, this uses a localized origin for the view matrix to reduce jitter at high zoom levels.
Using global coordinates runs into the limitations of float precision, which manes that small movements are functionally rounded by that precision. When panning at high zoom levels this manifests as jitter where the features jump between discrete locations instead of panning smoothly. The default is to use the first coordinate of the data of the feature for the origin. For features that span a large area, this will not help the jitter far from that coordinate (but won't be any worse that before this PR). The origin function is exposed on the style object, so if a large area feature is needed, the application can bind geo.event.pan to recompute the origin upon significant changes in the map center at high zoom values.
Resolves #831.