Omega Chess & Nebiyu

[hgm]

Would it be possible to configure Nebiyu for Omega Chess? The board there is basically 12x12, but the main difficulty there might be that (except for the corner squares) the edge squares must be inaccessible.

[Daniel Shawul]

Yes it is possible. I am sure it is in the alien's games list already. I don't recall exactly how I supported boards which do not fill the whole rectangle but I think some squares are permanently water some are land. So all that is needed is a standard letter for representing water squares. Triple chess and quadruple chess also have similarly shaped boards IIRC.

[hgm]

Didn't we agree on using # in the setup FEN for indicating inaccessible squares?

In principle it should be possible to play Omega Chess in the normal version of WinBoard as 12x12+0_fairy. It is a quite ordinary Chess variant, without any weirdness that WinBoard would not understand. This wouldn't black out any of the inaccessible squares, though, but they could be left empty. Or it could simply let WinBoard put a dummy piece on it, for which the user could define a bitmap of a square-filling blackness.

We could also agree to use the lower-case x to indicate inaccessible squares. The current WinBoard move parser would choke on pieces indicated by x, as it would confuse it for the SAN capture sign. So not much would be lost if we let engines indicate inaccessible squares with x in the setup FEN, and define it in the pieceToCharTable as a black piece not otherwise occurring in the variant (e.g. the Lance in case of Omega Chess). Purists could then provide a black bitmap, and configure WinBoard to use it for that piece. Future versions of WinBoard could black out such squares automatically, but it would provide perfect backward compatibility with the current and older WinBoard versions.

[Daniel Shawul]

Didn't we agree on using # in the setup FEN for indicating inaccessible squares?

I am using '*' to represent them but '#' should be fine too. Make sure that is not skipped as a comment though.

In principle it should be possible to play Omega Chess in the normal version of WinBoard as 12x12+0_fairy. It is a quite ordinary Chess variant, without any weirdness that WinBoard would not understand. This wouldn't black out any of the inaccessible squares, though, but they could be left empty. Or it could simply let WinBoard put a dummy piece on it, for which the user could define a bitmap of a square-filling blackness

Yes the important thing is the engine understands not to move a piece to inaccessible squares. As you said Winboard should work as it is. Since the game is in the alien list I can make a quick change to see if it will work by changing it to x. Note that right now I have to define 'x' as a new piece because nebiyu understands '*' as a water square. Ofcourse I can change the default to be 'x' later.
Edit: 'X' is chameleon in Ultima so maybe some other letter. The changes I needed to make are very small. My piece chars had empty and inacessible squaes as '.*' so changing them externally should work just fine.

Future versions of WinBoard could black out such squares automatically, but it would provide perfect backward compatibility with the current and older WinBoard versions.

Yes this is good. It is possible to support many games,even something not at all related to board games. I don't know how you supported dark chess but the darkened squares could be represented by 'x' as well, and for games with a 'fog of war', the engine can dynamically update additional inaccessible squares when they become visible after some moves etc.

[Daniel Shawul]

Ok there was a bug with the latest version of nebiyualien that prevented it from playing a game. I corrected that now but i could not select omegachess from winboard45-tm because i removed combo box selection of games. Also I have a problem with '#' because I also use it to represent comment in the ini file. Omegachess is actually playable with '#' since the corner squares are accessible, but triplechess/quadruple chess start with inacessible squares so it crashes. Anyway we can use 'x' , since its use for chameleon in ultima was internal thus can be replaced by any other letter. It would be great if you can add now a list of variants sent from an alien engine. I think that is what we decided up on last time instead of the clumsy way of handling it through combo box.