I am using the iOS 7 MapKit APIs to produce 3D camera movements on a map that displays an MKDirectionsRequest-produced path. The path is rendered by MKOverlayRenderer like so:
-(void)showRoute:(MKDirectionsResponse *)response
{
for (MKRoute *route in response.routes)
{
[self.map
addOverlay:route.polyline level:MKOverlayLevelAboveRoads];
}
}
- (MKOverlayRenderer *)mapView:(MKMapView *)mapView rendererForOverlay:(id < MKOverlay >)overlay
{
MKPolylineRenderer *renderer =
[[MKPolylineRenderer alloc] initWithOverlay:overlay];
UIColor *mapOverlayColor = [UIColor colorWithRed:((float)22 / 255.0f) green:((float)126 / 255.0f) blue:((float)251 / 255.0f) alpha:0.8];
renderer.strokeColor = mapOverlayColor;
renderer.lineWidth = 13.0;
return renderer;
}
It's working well except for one issue. When I zoom or pan around the path with MKMapCameras (and without them, if I simply do so as the user), the path is jagged as shown in this screenshot:
I tested to see if switching to MKOverlayLevelAboveLabels makes a difference but sadly the outcome was the same.
Does anyone have suggestions as to how to improve the rendering? Does switching to a geodesic path make a difference and if so, how would I implement this here?
Subclass MKPolylineRenderer and override applyStrokePropertiesToContext:atZoomScale: so that it ignores the scale, and draws lines at constant width:
@interface ConstantWidthPolylineRenderer : MKPolylineRenderer
@end
@implementation ConstantWidthPolylineRenderer
- (void)applyStrokePropertiesToContext:(CGContextRef)context
atZoomScale:(MKZoomScale)zoomScale
{
[super applyStrokePropertiesToContext:context atZoomScale:zoomScale];
CGContextSetLineWidth(context, self.lineWidth);
}
@end
Now use it and admire its smooth rendering:
- (MKOverlayRenderer *)mapView:(MKMapView *)mapView rendererForOverlay:(id<MKOverlay>)overlay
{
MKPolyline *polyline = (MKPolyline *)overlay;
ConstantWidthPolylineRenderer *renderer = [[ConstantWidthPolylineRenderer alloc] initWithPolyline:polyline];
renderer.strokeColor = [UIColor redColor];
renderer.lineWidth = 40;
return renderer;
}
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