There has been a brief discussion in the bugtracker. I just thought I push it early because otherwise I don't get people to use/test it anyway. The primary motivation for me is that loam bridges and moving liquids preserve the background material and texture, which comes for free without having to modify any existing maps.

> This can be used to prevent flowing liquids to overwrite the tunnel texture, but also to have infinite reappearing of liquids.

Or also infinite gold mines :), or indestructible granite.

> What will happen internally when I put background material to water at some point in the landscape and rock in front and then blast the rock? It seems that once the normal material is blasted the water at those points in the landscape move to the foreground to create a flood. Some detailed explanation would be nice to have.

What happens is that simply when a pixel is cleared, e.g. by digging or blasting, instead of either creating tunnel or sky where the pixel was, the pixel is changed to the background material. Afterwards, both the foreground and background materials are the same. When building loam bridges, or when the MassMover moves liquid around, it only changes the foreground material and leaves the background material as it is.

> Since we now have 255 indexes free for materials, should we reorder them more sensibly in the TexMap? Also the comment "# Index +128 for underground materials" is obsolete.

The index 255 is reserved for internal use, so in fact there are "only" 254 indices available (and 0 is always sky). In order to preserve backwards compatibility, the "index + 128 for underground" is still true for Map.bmp maps. If you want to make use of the full set of 254 indices, use a file MapFg.bmp instead (MapBg.bmp can then be used to specify the background materials). For other map types such as Map.c there is no such restriction (see the documentation for how to draw background materials with Map.c scripts).

> In the editor, the sky texture is greyed out but not set to none, to be consistent it should be set to none. Also, when I select sky as foreground the background is greyed out and equals sky, is there a reason for that? Tunnel can have background materials, which is a bit inconsistent somehow.

Sky has always been somewhat special, e.g. it does not have a texture compared to all other materials. But the major reason I think is just that it doesn't seem to make sense that there could be something "behind" sky. I'm not even sure what would happen at the moment if you have sky with say tunnel as background material and start to dig around in the sky region... but I don't have a very strong opinion on it, and it can be easily changed.

> The bucket of paint tool I can't select when drawing a landscape.

If I remember correctly that tool only works in exact landscape mode, but it has always been like that. Did you try that? Otherwise sounds like a bug...