screens are from 16k build, where I have cca 1,25m per pixel. If you look at the sceens, you can see very fine small details on the terrain (the first picture), also you can compare width of river to tree (tree is cca 17m high). So resolution of heightmap is really not the cause. It is very easy to fix these issues by hand in game engine (on the small scale, not for Kms of rivers), which only confirms, that heightmap resolution is enough.
Problem are not only long straight lines (this is actually the least problem), but there is not one single curve, everything is from straight lines (i know, vector graphics…). On the last picture of the first post is evident, that even very short parts and meanders are minecraft like. On the picture in my last post (after “post processing”) is showed, that this minecraft issue was removed, (blur+displacement), but river bank is broken somewhere.
This problem is not much visible in low res builds, but once you go higher, it starts to be evident and increasing resolution of HM does not help at all.
I really cant use rivers like this, I tried some post processing and it helps, but solution is quite complex, far from perfect and I have to do it for each mask, so my already complex project becames nightmare. So this is issue, which must be solved on device level. What about some antialiasing for the river line?
Note: this issue is not much visible in WM renderer (it does not display any detail above 4k), it must be imported into any game engine.
Meander, there is at least 10-12px for width of the river :
4k render in WM and import in game engine: