Help writing a modeline to rotate the picture 90 degrees on a CRT

[Yakkers]

I've seen a few people use VGA scaler custom video modelines to rotate the picture 90 degrees, such as here, mainly to play tate games on a horizontal rotation display.

I have a Mistercade in a CRT candy cab and I mostly play shmups so I like to leave it in tate, but I have just a few horizontal games I'd like to play so I'm looking to do the reverse. Depending on the game I'd either want to resample it down to fit or just keep it full resolution and have it go offscreen, for instance on something like Tetris the Grandmaster where I only need to see the center anyways.

I've been doing a lot of research on modelines but can't really figure out what causes the actual image rotation. It doesn't seem to be a very common use case so I haven't found many examples. For starters I'm specifically looking to do it with the PSX core for the TGM1 PSX romhack.

If this is actually a thing that's possible, can anyone with experience writing modelines tip me in the right direction? I'm a little afraid to just experiment because I'm not sure if I could end up telling my CRT to do something that would damage it.

Thanks in advance for any help!

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[FoxbatStargazer]

Modelines do not rotate the image. Only the core itself can, and you can tailor a modeline to match that rotation. If the core itself doesn't include a rotate option in its menu there isn't much you can do, unless you want to edit the source itself in verilog/HDL or whatever.

There is an ini option for rotating the OSD only, not the games.

[Yakkers]

Modelines do not rotate the image. Only the core itself can, and you can tailor a modeline to match that rotation. If the core itself doesn't include a rotate option in its menu there isn't much you can do, unless you want to edit the source itself in verilog/HDL or whatever.

There is an ini option for rotating the OSD only, not the games.

I see, that's what I was afraid of. I've had a few people point me towards modelines for this but I couldn't find anything about rotation itself with them so I was thinking maybe there was a miscommunication and it's just a way to align the picture once you have it rotated via other means.

Thanks for the heads up though, maybe I'll poke around the PSX core's source (or just get someone to help me rotate the CRT lol)

[FoxbatStargazer]

Modelines do not rotate the image. Only the core itself can, and you can tailor a modeline to match that rotation. If the core itself doesn't include a rotate option in its menu there isn't much you can do, unless you want to edit the source itself in verilog/HDL or whatever.

There is an ini option for rotating the OSD only, not the games.

I see, that's what I was afraid of. I've had a few people point me towards modelines for this but I couldn't find anything about rotation itself with them so I was thinking maybe there was a miscommunication and it's just a way to align the picture once you have it rotated via other means.

Thanks for the heads up though, maybe I'll poke around the PSX core's source (or just get someone to help me rotate the CRT lol)

Should note that the core author Robert was requested this feature multiple times (mostly for tate shooters on horizontal HDMI displays) but deemed it too difficult/time consuming. Even scandoubler is not supported. I think he threw in a 180 flip just because it was simple enough.

[dickhardpill]

Which Tetris is that?

[zakk4223]

That's the Tetris the Grand Master conversion to Playstation. Originally an arcade game that runs on the PSX based ZN-2 hardware