At some zoom levels some tiles are not rendered

[kezara]

Hello, I have issues with rendering of mbtiles, as you can see from attached screenshots. At some zoom level some tiles are not rendered. I've used tiles made with TileMaker from extract downloaded from Geofabrik.
I'm not sure what zoom level is on the first image, but zoom on second is higher than zoom on the first, and zoom on third image is higher than zoom on second.

[kezara]

In addition to first comment, second image is at zoom 13, and third at zoom 14.

Also, I've noted that when I'm using MapsUI instead of missing tiles I can see tiles from previous zoom levels, which are blurry and have lot of pixelation, and this is not the only location where it is visible (or not visible)

[AliFlux]

@kezara please check if the tiles generated from TileMaker are complete. It's possible that some tiles are missing in the mbtiles.

Furthermore, you can also put breakpoints to observe exceptions and null values. It may help you debug your tileset

[kezara]

@AliFlux thanks for reply. In method public async static Task<BitmapSource> Render(Style style, ICanvas canvas, int x, int y, double zoom, double sizeX = 512, double sizeY = 512, double scale = 1, List<string> whiteListLayers = null) in if (layer.Source.Type == "vector") I've sent to output all tiles that are null, and number of tiles that can't be loaded is about the same as number of the missing tiles on the screen. So, I'd say that those tiles are missing from mbtiles file, am I right?

[kezara]

@AliFlux
After systemed helped me to confirm that issue is not in the mbtiles file, I debugged the VectorTileRenderer for two tiles that are missing (and I guess that same issue is with other missing tiles) and found the following:

Tiles that have been debugged are

1. 4547, 5255, zoom 13 (osm tiles 4547, 2936)
2. 4546, 5254, zoom 13 (osm tiles 4546, 2937)

For both tiles exception is thrown in method PbfTileSource.baseTileToVector(object baseTile) on the transportation layer on the line vectorFeature.Attributes = feat.GetProperties();

For the first tile exception has been thrown when i == 11, and for second when i == 20, in both cases feature is LineString.

This is the exception that is thrown on feat.GetProperties() line:

• $exception	{"An item with the same key has already been added. Key: class"}	System.ArgumentException
  

• Data	{System.Collections.ListDictionaryInternal}	System.Collections.IDictionary {System.Collections.ListDictionaryInternal}
  HResult	-2147024809	int
  HelpLink	null	string
  

• InnerException	null	System.Exception
  Message	"An item with the same key has already been added. Key: class"	string
  ParamName	null	string
  SerializationRemoteStackTraceString	null	string
  SerializationStackTraceString	Evaluation of method System.Exception.get_SerializationStackTraceString requires calling method System.Reflection.MethodInfo.CreateDelegate, which cannot be called in this context.	string
  SerializationWatsonBuckets	null	object
  Source	"System.Private.CoreLib"	string
  StackTrace	"   at System.ThrowHelper.ThrowAddingDuplicateWithKeyArgumentException[T](T key) in /_/src/libraries/System.Private.CoreLib/src/System/ThrowHelper.cs:line 187\r\n   at System.Collections.Generic.Dictionary`2.TryInsert(TKey key, TValue value, InsertionBehavior behavior) in /_/src/libraries/System.Private.CoreLib/src/System/Collections/Generic/Dictionary.cs:line 608\r\n   at System.Collections.Generic.Dictionary`2.Add(TKey key, TValue value) in /_/src/libraries/System.Private.CoreLib/src/System/Collections/Generic/Dictionary.cs:line 195\r\n   at Mapbox.VectorTile.VectorTileFeature.GetProperties()\r\n   at VectorTileRenderer.Sources.PbfTileSource.<baseTileToVector>d__15.MoveNext() in E:\\Users\\Borko\\Source\\Repos\\GMap.Net_Demo\\VectorTileRenderer\\Sources\\PbfTileSource.cs:line 115"	string
  

• TargetSite	{Void ThrowAddingDuplicateWithKeyArgumentException[T](T)}	System.Reflection.MethodBase {System.Reflection.RuntimeMethodInfo}
  _HResult	-2147024809	int
  _data	null	System.Collections.IDictionary
  _dynamicMethods	null	object[]
  _exceptionMethod	null	System.Reflection.MethodBase
  _helpURL	null	string
  

• _innerException	null	System.Exception
  _ipForWatsonBuckets	0x00007ffc939824d5	System.UIntPtr
  _message	"An item with the same key has already been added. Key: class"	string
  _paramName	null	string
  _remoteStackTraceString	null	string
  _source	null	string
  

• _stackTrace	{byte[192]}	byte[]
  _stackTraceString	null	string
  _watsonBuckets	null	byte[]
  _xcode	-532462766	int
  _xptrs	0x0000000000000000	System.IntPtr
  

• Static members
  

and on the return from PbfTileSource.baseTileToVector(object baseTile) exception looks like:

• System.Runtime.CompilerServices.AsyncTaskMethodBuilder<TResult>.SetException returned	Id = 486, Status = Faulted, Method = "{null}", Result = "{Not yet computed}"	System.Threading.Tasks.Task<VectorTileRenderer.VectorTile>
  AsyncState	null	object
  CancellationPending	false	bool
  CreationOptions	None	System.Threading.Tasks.TaskCreationOptions
  

• Exception	Count = 1	System.Exception {System.AggregateException}
  

• Data	{System.Collections.ListDictionaryInternal}	System.Collections.IDictionary {System.Collections.ListDictionaryInternal}
  HResult	-2146233088	int
  HelpLink	null	string
  

• InnerException	{"An item with the same key has already been added. Key: class"}	System.Exception {System.ArgumentException}
  InnerExceptionCount	1	int
  

• InnerExceptions	Count = 1	System.Collections.ObjectModel.ReadOnlyCollection<System.Exception>
  Message	"One or more errors occurred. (An item with the same key has already been added. Key: class)"	string
  SerializationRemoteStackTraceString	null	string
  SerializationStackTraceString	null	string
  SerializationWatsonBuckets	null	object
  Source	null	string
  StackTrace	null	string
  TargetSite	null	System.Reflection.MethodBase
  _HResult	-2146233088	int
  

• _data	{System.Collections.ListDictionaryInternal}	System.Collections.IDictionary {System.Collections.ListDictionaryInternal}
  _dynamicMethods	null	object[]
  _exceptionMethod	null	System.Reflection.MethodBase
  _helpURL	null	string
  

• _innerException	{"An item with the same key has already been added. Key: class"}	System.Exception {System.ArgumentException}
  _ipForWatsonBuckets	0x0000000000000000	System.UIntPtr
  _message	"One or more errors occurred."	string
  _remoteStackTraceString	null	string
  _source	null	string
  _stackTrace	null	byte[]
  _stackTraceString	null	string
  _watsonBuckets	null	byte[]
  _xcode	-532462766	int
  _xptrs	0x0000000000000000	System.IntPtr
  

• m_innerExceptions	Count = 1	System.Collections.ObjectModel.ReadOnlyCollection<System.Exception>
  

• Static members		
  Id	486	int
  Result	null	VectorTileRenderer.VectorTile
  Status	Faulted	System.Threading.Tasks.TaskStatus
  

• Raw View
  

and below is the screenshot of the feature where it breaks and sends null tile for 4547, 5255, zoom 13

Could you please see what's the issue here and how to fix it. Many thanks.

[AliFlux]

Can you please share the tileset? It may be easier to debug it that way

[kezara]

Please see this answer, I think it will make this issue more clearer and will cost you less time than debugging. According to the answer, issue is not in your code, issue is with MapBox method Mapbox.VectorTile.VectorTileFeature,GetProperties() as it returns Dictionary<string,object>() which can't accept duplicate keys...In the meantime systemed has changed his code so now TileMaker doesn't create duplicate tags...

In your project, I've replaced Mapbox Nuget dependencies with projects from Mapbox and changed GetProperties() to return List<KeyValuePair<string, object>>() and I've changed your code accordingly. I'm not tested this extensively, and I'm not sure if it can impact to something else (as I could see it should not have any impact), but with this change mbtiles with duplicate tags are shown correctly, at least this mbtiles file.

Here are mbtiles