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NROM Mirroring

Posted: Wed Oct 17, 2018 2:09 pm
by battagline
Can an NROM cart change it's mirroring on the fly? Or can that only be done with a mapper?

Thanks

Re: NROM Mirroring

Posted: Wed Oct 17, 2018 2:25 pm
by lidnariq
Only with some mapper.

FDS might pedantically count as close enough to NROM, with mirroring control, for your purposes. Maybe.

Re: NROM Mirroring

Posted: Wed Oct 17, 2018 2:51 pm
by battagline
lidnariq wrote:Only with some mapper.

FDS might pedantically count as close enough to NROM, with mirroring control, for your purposes. Maybe.
I was going to make the largest asteroids in my asteroids clone background tiles. They would all have to more in the same direction, but if I had it set up to mirror in all directions, the asteroids could loop around pretty easily even if I had them moving at odd angles. The only problem was I used horizontal mirroring to scroll in the name of the game on the start screen. Anyway, if I can't change the mirroring I can just have the largest asteroids move horizontally only. Kinda boring, but this is just a learning project so it's not the end of the world.

Thanks.

Re: NROM Mirroring

Posted: Wed Oct 17, 2018 2:57 pm
by lidnariq
If you just want fixed 1-screen mirroring, you could target MMC1, ANROM, or mapper 28.

Re: NROM Mirroring

Posted: Wed Oct 17, 2018 3:29 pm
by battagline
lidnariq wrote:If you just want fixed 1-screen mirroring, you could target MMC1, ANROM, or mapper 28.
I'm not going to use a mapper for this game. I'm just trying to get something done and trying to keep it as simple as possible.

I want to figure out Mappers soon, but I'd like to get this game finished up this week, and I'm just not ready for mappers quite yet... soon though :-)

Thanks

Re: NROM Mirroring

Posted: Wed Oct 17, 2018 3:39 pm
by lidnariq
Sure. I meant that you can use some conceptual mapper produce something that looks like NROM with fixed 1-screen mirroring. The actual hardware would still be NROM with fixed 1-screen mirroring.

Re: NROM Mirroring

Posted: Wed Oct 17, 2018 4:01 pm
by yaros
battagline wrote:Anyway, if I can't change the mirroring I can just have the largest asteroids move horizontally only. Kinda boring, but this is just a learning project so it's not the end of the world.
Thanks.
If you asteroid is smaller than the screen, you can still scroll vertically and dynamically load/unload rows of the image. You will have disappearing/appearing textures on the top and the bottom though.

Image below, if it makes sense. Green is when you load next part of the asteroid, when it's bottom is 8px above the bottom of the screen.

Re: NROM Mirroring

Posted: Wed Oct 17, 2018 4:26 pm
by battagline
yaros wrote:
battagline wrote:Anyway, if I can't change the mirroring I can just have the largest asteroids move horizontally only. Kinda boring, but this is just a learning project so it's not the end of the world.
Thanks.
If you asteroid is smaller than the screen, you can still scroll vertically and dynamically load/unload rows of the image. You will have disappearing/appearing textures on the top and the bottom though.

Image below, if it makes sense. Green is when you load next part of the asteroid, when it's bottom is 8px above the bottom of the screen.
yes, but aren't you moving it 8 pixels at a time?

Re: NROM Mirroring

Posted: Wed Oct 17, 2018 4:38 pm
by tokumaru
battagline wrote:yes, but aren't you moving it 8 pixels at a time?
You can move it smoothly, but the NT will only be changed every 8 pixels, which will cause a "pop" effect if the TV doesn't hide a portion of the picture at the edges of the screen. Lots of programmers (including programmers that worked in commercial games back in the day) counted on these kinds of glitches near the edges of the screen to be hidden, or at least not too distracting, because MANY games suffer from this.

Re: NROM Mirroring

Posted: Wed Oct 17, 2018 5:42 pm
by yaros
If your big asteroid is not very big, you can also cover the edge with multiple black sprites. So "popping" will always be hidden.