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04-20-24 05:23 PM |
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| 0 users currently in ROM Hacking | 3 guests |
| Main - ROM Hacking - I don't believe in giving up... | New thread | New reply |
| never-obsolete |
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 Rat Level: 24 Posts: 13/96 EXP: 74461 Next: 3664 Since: 02-22-07 From: Phoenix, AZ Last post: 2590 days Last view: 2590 days |
here's a visual that might help. the image is kinda big so i linked to it. the red grid lines on the left picturebox are the same as the black ones on the right picturebox and are not part of the scene.
edit: make sure to view the image fullsize or it'll look distorted. |
| RetroRain |
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 Fuzz Ball Level: 66 Posts: 25/994 EXP: 2437034 Next: 24817 Since: 09-30-07 Last post: 1929 days Last view: 951 days |
I added another 8K of CHR ROM. Do you have to add a mapper to be able to swap it in? I want to use two different pattern tables obviously. I been searching through some documents, not sure what to look for. ____________________ My YouTube Channel |
| jargon |
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 Ninji Banned until 2010-10-15 for an utterly psychedelic posting style Level: 36 Posts: 20/247 EXP: 300097 Next: 8013 Since: 12-10-07 From: 480/85260 Last post: 4943 days Last view: 4601 days |
the channel has come to a consensus that your chr ram/rom is overwriting into nametable space. ____________________ NIHYFDTTMWTMR |
| Kawa |
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 CHIKKN NI A BAAZZKIT!!! 80's Cheerilee is best pony Level: 138 Posts: 645/5344 EXP: 30930736 Next: 732245 Since: 02-20-07 From: The Netherlands Last post: 4492 days Last view: 2627 days |
The channel has come to the consensus that you're a jerk. ____________________ Wife make lunch - Shampoo Opera - give it a spin Spare some of your free time? <GreyMaria> I walked around the Lake so many goddamn times that my sex drive was brutally murdered Kawa rocks  — byuu |
| RetroRain |
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Fuzz Ball Level: 66 Posts: 26/994 EXP: 2437034 Next: 24817 Since: 09-30-07 Last post: 1929 days Last view: 951 days |
hey jargon, since you know how to do it, why don't you show me? ____________________ My YouTube Channel |
| jargon |
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Ninji Banned until 2010-10-15 for an utterly psychedelic posting style Level: 36 Posts: 23/247 EXP: 300097 Next: 8013 Since: 12-10-07 From: 480/85260 Last post: 4943 days Last view: 4601 days |
rockman:
Kawa was spamming by refering to me, pay no attention to Kawa, Kawa apparently doesn't know jack to nothing about the NES nor anything 80s for that matter. i know little, but i do understand the physical limitations in 80s circuitry layouts. for example: you can't simply map the entire screen as one big CHR block. it will overwrite nametable space, however you can store it in multiple CHR blocks and bankswitch mid-retrace using scanline IRQ in order to switch banks partially down the screen when the NES draws it. in this manner you can store 1/4th of unique tiles covering the entire screen in its own CHR bank, that is swapped out via IRQ that triggers the swap when the NES arrives at the correct scanline. mid-scanline IRQ is out of the question tho as far as i am concerned. i haven't heard of a damned NES cart that splits it into left and right CHR sets. only multiple top down CHR sets. so keep that in mind. the irc channel came to the consensus that your CHR is overwriting NAMETABLE space, and this would produce the odd debug artifacts your emu is giving you that you show in your screen shots. yes it would cause such effects as some tiles being scrambled, "squished" on an axis, or missing in entirety in theory. i suggest you use a different mapper that bankswitches using scanline triggered IRQ for when rendering full screen prerendered details. i suggest keeping sprites in one 1k bank, and your prerendered backdrops in multiple scanline-IRQ-swapped 1k pattern tables. you can also swap your sprite pattern table (CHR) using the scanline-irq so that the hud gfx and npcs etc have more pattern table space, just make sure the hud and npc's always stay on their own side of a specific scanline. remember, you can change the pattern table mid sprite or tile using the scanline IRQ for bankswap, just make sure the pattern tables match up. ciao ____________________ NIHYFDTTMWTMR |
| RetroRain |
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Fuzz Ball Level: 66 Posts: 27/994 EXP: 2437034 Next: 24817 Since: 09-30-07 Last post: 1929 days Last view: 951 days |
no wait, did you think I was trying to map the whole screen using 1 CHR bank? No, if I was vague, I'm sorry. What I meant to say is, if you have 4 pattern tables for example, how do you replace the two that are already loaded, with the next two? It can only hold 2 pattern tables at a time. I want to load 2 new ones in. Now I'm guessing that they had to be swapped in. ____________________ My YouTube Channel |
| jargon |
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Ninji Banned until 2010-10-15 for an utterly psychedelic posting style Level: 36 Posts: 24/247 EXP: 300097 Next: 8013 Since: 12-10-07 From: 480/85260 Last post: 4943 days Last view: 4601 days |
Posted by Rockman Posted by Rockman i suggest looking for tutorials on how to bankswitch based on scanline IRQ. if you took part in #acmlm on irc.kafuka.org (EmuNet) or #nesdev on irc.choopa.ca (EFnet) you could prolly find many people that would be more experienced to lend a hand. i am planning on compiling using nesasm using nbasic as a precompiler for my homebrew NES carts, and don't plan on diddling with any assembler what-so-ever until i have done enough research on how things work in order to make a bread board prototype that mimics the behavior of how the NES operates as a win32 binary of my games first. assembler is basically only do-able once you already have a full idea of what you intend to actually code. unless you are a damned asm guru which i seem to doubt. ____________________ NIHYFDTTMWTMR |
| RetroRain |
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Fuzz Ball Level: 66 Posts: 28/994 EXP: 2437034 Next: 24817 Since: 09-30-07 Last post: 1929 days Last view: 951 days |
I figured out how to do it. After doing a lot of searching around, I came upon Disch's document:
http://www.romhacking.net/docs/353/ It is there that I found out that you DO indeed need to add a mapper, if you want to swap banks in and out, because the mappers are special chips that expand the capabalities of the limited NES. By adding a mapper, which can be different for any ROM, you can really do a lot more! I never really quite got the concept of the mapper in the past, but now I have a much better understanding of it. Otherwise, by default, you're limited to what is already there, which is the 2 pattern tables. I know you can also add graphics another way, by putting them in the PRG bank, but that's a whole different thing. So after I read that, I got a much better understanding of how mappers work, and how to swap stuff in and out. However, even after reading his doc, I still didn't know exactly how to do it, until I found this document: http://emu-docs.org/NES/Mappers/mappers.txt Then it all became clear. I added a MMC3 (Mapper 4) to my ROM, and used the swapping capabilities to change what can be shown in the 1K CHR slots. Its pretty neat. In a way, building this little project from scratch, will really help me now when it comes to ROM hacking.
Now, press Start... 
Press A... 
Swapped those babies in!
I still didn't get around to figuring out the Attribute Tables, but I'm going to deal with that next. When I am done with this project, I might make a document which shows everything I learned in programming the NES, that way others can learn from it as well. ____________________ My YouTube Channel |
| Main - ROM Hacking - I don't believe in giving up... | New thread | New reply |
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