if you look into the sky in the first section of the map, there are thin lines that are quite noticeable

That would be the skybox...I dunno how to fix it, though. I've seen the lines in a LOT of games...professional and indie....

I know how to fix it.

sometimes, instead of a box, you need a circle...

?

How Gez, how?

Basically, by wasting memory to make the textures larger.

For each side, create a texture (using the TEXTURES editor) that is two times the height and width of the source texture, which we'll use as a patch.

Center the patch at the bottom of the texture.

Add the top texture as a patch (rotated or mirrored as appropriate) on the top of the patch. Add the adjacent sides of the skybox as patches on the two other sides.

Then edit the skybox's geometry in the map. Add offsets to make it display correctly.

The lines appear because the texture is tiled, then applied to the surface by the renderer. So the border pixels are interpolated with the pixels on the other side. If you make the cut in the geometry at a place that isn't the border of the texture, the pixels will be interpolated with their neighbors which are the pixels that are used on the adjacent face, so there will be no problem.

Wouldn't have a smaller sector (2pixels in each direction) have the same effect?

It's a bit of the same idea; the big difference being that the existing textures are meant to be stitched as they are, not two texels away from their borders. I don't think the resolution is huge enough that columns of four pixels missing at each angle will go unnoticed...

I actually silently did just that at my phase 1 slot and nobody here took notice.