About glitches

Discuss emulation of the Nintendo Entertainment System and Famicom.

Moderator: Moderators

Post Reply
Boolean
Posts: 87
Joined: Thu Jan 02, 2014 7:58 am
Contact:

About glitches

Post by Boolean » Thu Jan 02, 2014 8:36 am

Hello,everyone! :)
I have a problem on my emulator. My emulator use loopy's The skinny on NES scrolling
The graphics generate glitches, some games at scanline 0 , and some demos at every visible scanline.(scanline scope is -1 ~ 260, -1 represents pre-renderline, 0 ~ 239 represents visible scanlines, 240 represents post-renderline, 241 ~ 260 represents vblank stuff)

Here are some pictures

Image
Image
Image
Image
Image
Image

What's wrong?

I guess the reasion maybe $2005 write
Last edited by Boolean on Sun Oct 26, 2014 4:42 am, edited 1 time in total.
1. I am not a native speaker of English.If my expression is not right or has grammar errors or something, please correct me by PM or reply to my post directly.Thank you in advance.
2. About FC87.

Boolean
Posts: 87
Joined: Thu Jan 02, 2014 7:58 am
Contact:

Re: About glitches

Post by Boolean » Thu Jan 02, 2014 9:20 am

who can help me? :?
1. I am not a native speaker of English.If my expression is not right or has grammar errors or something, please correct me by PM or reply to my post directly.Thank you in advance.
2. About FC87.

User avatar
Quietust
Posts: 1500
Joined: Sun Sep 19, 2004 10:59 pm
Contact:

Re: About glitches

Post by Quietust » Thu Jan 02, 2014 9:33 am

1. Expecting a reply within 1 hour of your initial post is unreasonable - some of us only check this forum once per day, often even less frequently.

2. Do not expect older demo ROMs to work correctly, since most of them were designed to work on emulators and were never verified to work correctly on real hardware. It's entirely possible that those glitches are supposed to appear. Similarly, always check this list before trying to "fix" graphical glitches in a particular game.

3. It looks like you're using an outdated version of scanline.nes (the 2nd-last picture) - use this one instead.
Quietust, QMT Productions
P.S. If you don't get this note, let me know and I'll write you another.

User avatar
tokumaru
Posts: 11520
Joined: Sat Feb 12, 2005 9:43 pm
Location: Rio de Janeiro - Brazil

Re: About glitches

Post by tokumaru » Thu Jan 02, 2014 11:24 am

Some games (mostly early ones) set the vertical scroll to -1 in order to compensate for the 1 scanline delay in sprite coordinates. This may cause attribute table data to be rendered as name table data in the first scanline of the screen, which most of the time will look like garbage. Since this isn't visible in most TVs, the problem was never detected by the developers. You should check each game (in other emulators and possibly a real console though video capture) to verify whether it's supposed to have those glitches before trying to fix them.

User avatar
Dwedit
Posts: 4251
Joined: Fri Nov 19, 2004 7:35 pm
Contact:

Re: About glitches

Post by Dwedit » Thu Jan 02, 2014 12:11 pm

CMCWavy and Soccer look correct on Nintendulator, so the roms probably aren't the problem here. Try posting a screenshot of Slalom, that game uses both negative scroll and lots of horizontal scroll changes.
Here come the fortune cookies! Here come the fortune cookies! They're wearing paper hats!

Boolean
Posts: 87
Joined: Thu Jan 02, 2014 7:58 am
Contact:

Re: About glitches

Post by Boolean » Thu Jan 02, 2014 7:45 pm

Dwedit wrote:CMCWavy and Soccer look correct on Nintendulator, so the roms probably aren't the problem here. Try posting a screenshot of Slalom, that game uses both negative scroll and lots of horizontal scroll changes.
Image

Slalom has glitches too. The same problem occured in F1 Race

Somehow, I always think the reason is that I didn't properly deal with first write to $2005 to change coarse X(Tile Number) and find x.
Do you agree with me?
1. I am not a native speaker of English.If my expression is not right or has grammar errors or something, please correct me by PM or reply to my post directly.Thank you in advance.
2. About FC87.

Boolean
Posts: 87
Joined: Thu Jan 02, 2014 7:58 am
Contact:

Re: About glitches

Post by Boolean » Thu Jan 02, 2014 7:48 pm

tokumaru wrote:Some games (mostly early ones) set the vertical scroll to -1 in order to compensate for the 1 scanline delay in sprite coordinates. This may cause attribute table data to be rendered as name table data in the first scanline of the screen, which most of the time will look like garbage. Since this isn't visible in most TVs, the problem was never detected by the developers. You should check each game (in other emulators and possibly a real console though video capture) to verify whether it's supposed to have those glitches before trying to fix them.
I will disassemble the ROM to verify it.
1. I am not a native speaker of English.If my expression is not right or has grammar errors or something, please correct me by PM or reply to my post directly.Thank you in advance.
2. About FC87.

Boolean
Posts: 87
Joined: Thu Jan 02, 2014 7:58 am
Contact:

Re: About glitches

Post by Boolean » Thu Jan 02, 2014 7:58 pm

Quietust wrote:1. Expecting a reply within 1 hour of your initial post is unreasonable - some of us only check this forum once per day, often even less frequently.

2. Do not expect older demo ROMs to work correctly, since most of them were designed to work on emulators and were never verified to work correctly on real hardware. It's entirely possible that those glitches are supposed to appear. Similarly, always check this list before trying to "fix" graphical glitches in a particular game.

3. It looks like you're using an outdated version of scanline.nes (the 2nd-last picture) - use this one instead.
1. You are right, but I am a bit hurry. :)

2. Yeah. The page I accessed frequently. It's very useful to me. Simultaneously, Tricky-to-emulate games also important.

3. I am trying to understand your scanline.asm's every instruction
1. I am not a native speaker of English.If my expression is not right or has grammar errors or something, please correct me by PM or reply to my post directly.Thank you in advance.
2. About FC87.

WedNESday
Posts: 1236
Joined: Thu Sep 15, 2005 9:23 am
Location: Berlin, Germany
Contact:

Re: About glitches

Post by WedNESday » Fri Jan 03, 2014 4:37 am

Looks like a timing error to me.

Boolean
Posts: 87
Joined: Thu Jan 02, 2014 7:58 am
Contact:

Re: About glitches

Post by Boolean » Fri Jan 03, 2014 8:43 am

WedNESday wrote:Looks like a timing error to me.
Maybe, but I couldn't find the actual reason.
I guess sprite hit should be OK, because Battletoads could be run properly.
Do you know any test ROM for accurate timing?
1. I am not a native speaker of English.If my expression is not right or has grammar errors or something, please correct me by PM or reply to my post directly.Thank you in advance.
2. About FC87.

ArsonIzer
Posts: 115
Joined: Fri Jul 19, 2013 11:38 am

Re: About glitches

Post by ArsonIzer » Fri Jan 03, 2014 9:00 am

Boolean wrote:Do you know any test ROM for accurate timing?
CPOW once posted a link to the collection of test ROMs he had accumulated when I was having trouble with my CPU/PPU, and they helped a lot: https://github.com/christopherpow/nes-test-roms

Some of these are timing-related test ROMs. Maybe they will prove to be useful.

Boolean
Posts: 87
Joined: Thu Jan 02, 2014 7:58 am
Contact:

Re: About glitches

Post by Boolean » Fri Jan 03, 2014 9:20 am

ArsonIzer wrote:
Boolean wrote:Do you know any test ROM for accurate timing?
CPOW once posted a link to the collection of test ROMs he had accumulated when I was having trouble with my CPU/PPU, and they helped a lot: https://github.com/christopherpow/nes-test-roms

Some of these are timing-related test ROMs. Maybe they will prove to be useful.
Yeah!
Those ROMs were downloaded by me last year, and I did some tests.
Now, I think I should test ROMs about timing carefully.
1. I am not a native speaker of English.If my expression is not right or has grammar errors or something, please correct me by PM or reply to my post directly.Thank you in advance.
2. About FC87.

Boolean
Posts: 87
Joined: Thu Jan 02, 2014 7:58 am
Contact:

Re: About glitches

Post by Boolean » Sun Jan 05, 2014 7:13 am

apocalypse.png
I test a rom called apocalypse.nes.
Nametable window is ok, but FC87 main window is error.
It seems that nametable switch not properly.
I need to check The skinny on NES scrolling implementation in my emulator.

The demo apocalypse downloaded from https://github.com/christopherpow/nes-test-roms
1. I am not a native speaker of English.If my expression is not right or has grammar errors or something, please correct me by PM or reply to my post directly.Thank you in advance.
2. About FC87.

Boolean
Posts: 87
Joined: Thu Jan 02, 2014 7:58 am
Contact:

Re: About glitches

Post by Boolean » Wed Jul 16, 2014 8:56 am

I find a reason about horizon shaking. The reason is that my cpu's crossing page implementation
is wrong, and I no longer judge crossing page the video is better than ever.

for example
boing.png:
Judging crossing page left is shaking and right is shaking too.
Don't judge crossing page right is shaking only.
scanline.png:
Judging crossing page left is shaking and right is shaking too.
Don't judge crossing page neither left nor right is shaking.
Attachments
boing.png
scanline.png
1. I am not a native speaker of English.If my expression is not right or has grammar errors or something, please correct me by PM or reply to my post directly.Thank you in advance.
2. About FC87.

Post Reply