d668c0fa84
Greatly simplified conversions between zoom level and altitude. Adjusted field of view to more closely match MapKit. Conversions are now well within the same order of magnitude as MapKit at all latitudes. Fixes #2266.
47 lines
2.2 KiB
Plaintext
47 lines
2.2 KiB
Plaintext
#import "MGLGeometry_Private.h"
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#import <mbgl/util/projection.hpp>
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/** Vertical field of view, measured in degrees, for determining the altitude
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of the viewpoint.
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TransformState::getProjMatrix() assumes a vertical field of view of
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2 arctan ⅓ rad ≈ 36.9°, but MapKit uses a vertical field of view of 30°.
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flyTo() assumes a field of view of 2 arctan ½ rad. */
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const CLLocationDegrees MGLAngularFieldOfView = 30;
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const MGLCoordinateSpan MGLCoordinateSpanZero = {0, 0};
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CGRect MGLExtendRect(CGRect rect, CGPoint point) {
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if (point.x < rect.origin.x) {
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rect.size.width += rect.origin.x - point.x;
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rect.origin.x = point.x;
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}
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if (point.x > rect.origin.x + rect.size.width) {
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rect.size.width += point.x - (rect.origin.x + rect.size.width);
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}
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if (point.y < rect.origin.y) {
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rect.size.height += rect.origin.y - point.y;
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rect.origin.y = point.y;
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}
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if (point.y > rect.origin.y + rect.size.height) {
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rect.size.height += point.y - (rect.origin.y + rect.size.height);
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}
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return rect;
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}
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CLLocationDistance MGLAltitudeForZoomLevel(double zoomLevel, CGFloat pitch, CLLocationDegrees latitude, CGSize size) {
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CLLocationDistance metersPerPixel = mbgl::Projection::getMetersPerPixelAtLatitude(latitude, zoomLevel);
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CLLocationDistance metersTall = metersPerPixel * size.height;
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CLLocationDistance altitude = metersTall / 2 / std::tan(MGLRadiansFromDegrees(MGLAngularFieldOfView) / 2.);
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return altitude * std::sin(M_PI_2 - MGLRadiansFromDegrees(pitch)) / std::sin(M_PI_2);
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}
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double MGLZoomLevelForAltitude(CLLocationDistance altitude, CGFloat pitch, CLLocationDegrees latitude, CGSize size) {
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CLLocationDistance eyeAltitude = altitude / std::sin(M_PI_2 - MGLRadiansFromDegrees(pitch)) * std::sin(M_PI_2);
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CLLocationDistance metersTall = eyeAltitude * 2 * std::tan(MGLRadiansFromDegrees(MGLAngularFieldOfView) / 2.);
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CLLocationDistance metersPerPixel = metersTall / size.height;
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CGFloat mapPixelWidthAtZoom = std::cos(MGLRadiansFromDegrees(latitude)) * mbgl::util::M2PI * mbgl::util::EARTH_RADIUS_M / metersPerPixel;
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return ::log2(mapPixelWidthAtZoom / mbgl::util::tileSize);
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}
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