Are you sure your texture is tileable? It certainly doesn't look it. Try downloading a proper tiling texture, and see if the problem still exists..
when I use the complete texture (no chunking), it's continues. as was seen with the GL_NEAREST filter.
Are you sure your texture is tileable? It certainly doesn't look it.This strikes me as well. Given the random nature of your texture contents, it's not clear you'll be able to tell if it is tiling or not, since with sampling set to GL_NEAREST, it just looks like noise.
Try generating textures with larger-scale features, and see if the feature line up. My guess would be you have an small error in the texture coordinates at the edge of each tile.
You, sir are the real MVP . You are correct. The artifact only shows when the values between the neighboring chunk vary greatly. That should never happen in the real game. And when I fill my global blend map with sane values, the artifact is no more!! see the screenshot below to see the proof.
I think the uv mapping is not continuous, ie if an edge is shared between 2 quads, the uv value of vertex doesn't match.
(assuming that 2 quads uv map doesn't overlap)
The uv mapping is continuous. I've checked it thoroughly at the quadtree creation code.
Update:
Heheh, the artifact is virtually "lost" it only becomes visible when the neighboring chunk has pixel value that is very different. so in my noise texture test it's always visible. But now I've implemented the terrain paint brush. It seems perfect for now. Well the key is simply to not let the difference to be too great for the neighboring chunk's texels. And since it's for alpha map, it would be blurred anyway as to not make it look too sharp which is unnatural for terrain texture splatting. Thanks guys for your input!!
see? no visible artifact