Strange lines processed along tile borders

[demiantres]

While checking the VTM rendering pipeline with RenderDoc (https://renderdoc.org/) I noticed strange (invisible) lines drawn along the tile boundaries (OpenAndroMaps with Elevate theme). The following picture shows the lines in RenderDoc (the lines are invisible in the final map).:

The lines originate from: org.oscim.tiling.source.mapfile.MapFile processWays method and are drawn using the LineBucket.

Do these lines have a specific function?

[devemux86]

@demiantres If they are invisible, how are they visible?

Better ask OpenAndroMaps forum what they include in their maps and themes.
Could be a rectangle line for the border of the map.

Also tests should be made with VTM samples, so we can all test with library's reference app.
And try to see what happens when testing it with Mapsforge samples.

[demiantres]

With RenderDoc you can visualize all rendering calls. And for each tile there is this "strange" rendering call (everytime 12 vertices) which draws invisible lines (no fill and stroke) around each tile's border. I have also checked it with non-OAM-maps and the same happens there.

[demiantres]

Got it: The rectangles are used to clip away tile borders (using stencil).