PathLayer (regular) reverses

[devemux86]

PathLayer (regular) with a directed texture (e.g. arrow) shows reversed line segments at large zooms.
Probably LineClipper plays a role to that?

Note that JTS PathLayer works without issues.

[Gustl22]

Do you have an image or location on map where I can reproduce this? I recently worked with the clipper and maybe I can help here.

[devemux86]

Can use LineTexTest replacing with regular PathLayer and LineStyle.
Depending on latitude, the directed textures are reversed from around zoom 10.

Correct direction:

Reversed direction:

[devemux86]

Note: regular PathLayer had another issue with disappearing segments, fixed in #108.

[Gustl22]

Problem seems to be that line length in LineTexBucket is out of range of Short.MAX_VALUE at higher zoom levels.

Thus problem can happen in jts PathLayer, too, but never would, cause of smaller clipping values.

I did not find out why there's need of lineLength or where the OpenGL calculations take place. But theoretically this param is redundant.

As note: lineLength sums up the lengths of all line segments, so if total line is larger than the short limit, weird things can happen.

[devemux86]

Note that line stipples and textures didn't exist in master VTM.
They were introduced in #105 based on work by @hjanetzek.

[Gustl22]

@devemux86: As I can see you're much more experienced in OpenGL programming than me. Can you give me a hint where the lineLength is used in LineTexBucket.Renderer code (or attribute in shaders) after adding it to vertex items. I spent hours (also in Googles gapid) and didn't catch the concept.

[devemux86]

@hjanetzek wrote that part of VTM, so I need also to search first to find out that. 🙂

[Gustl22]

No sweat. Thought you might have an idea 🙂

[devemux86]

Fixed via #532.