Adventures of Batman & Robin (glitch during 2nd Boss)

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Eke
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Adventures of Batman & Robin (glitch during 2nd Boss)

Post by Eke » Wed Aug 17, 2011 4:38 pm

Image

Actually, these bugs happen in every emulators, but I left this here for easier bug references :wink:

This will happen after "Two Faces" drops bombs on you:

1) partial corrupted line on the top-right part of the screen: what happens is the game uses 2-cell VSCROLL mode and is modifying VSRAM data for that line during the previous line, which shifts into the HBLANK period for the two or three last values. Most emulators will either render the line or latch VSRAM before those last values got written and the two or three last 16-pixels columns are incorrectly rendered.

--> it means that VSRAM values are not latched in 2-cell VSCROLL mode and most likely read by the VDP before rendering each 16-pixels column. Analyzing game timings shows that it writes VSRAM values on the previous line AFTER the associated 16-pixel column has been rendered, so it will only takes effect on next line. From emulator point of view, it is only necessary to make sure that, in this mode, VSRAM writes during HBLANK are still taken in account for the upcoming line.


2) full corrupted line in the middle of the screen: what happens is the game is writing VDP register #4 during HBLANK to modify Plane B nametable address from that line. Most emulators will render this line at once before this address is changed and got it wrong.

--> it means that planes nametable registers are not latched at the start of the line and can probably be modified anytime during a line. As I see it, VDP regs #2 #3 and #4 are read by VDP before reading each pixel data block from VRAM. Again, from an emulator point of view, it is only necessary to make sure that, nametable changes during HBLANK are still taken in account for the upcoming line. I didn't verify if this is only the case in 2-cell VSCROLL mode but most likely not.


Funny that we are still finding games doing odd tricks like that, after all these years :?

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Stef
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Post by Stef » Thu Aug 18, 2011 8:36 am

Very nice finds :)
Batman & Robin is one of the most impressive genesis title when it comes to GFX and rasters effects. I'm not surprised to see that emulators doesn't reproduce it 100% accurately.

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Post by Eke » Thu Aug 18, 2011 8:50 am

I agree, the developers did an awesome job and each boss/stage has some original gfx effects...

But it's also damn hard, I had to use game genie codes to simply go to that part :oops:

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Post by Stef » Thu Aug 18, 2011 11:11 am

Eke wrote:I agree, the developers did an awesome job and each boss/stage has some original gfx effects...

But it's also damn hard, I had to use game genie codes to simply go to that part :oops:
Yeah the game is very difficult, i used a cheat code too to see next levels (you don't need game genie, some cheats exist to choose / change level ingame).

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Post by I.S.T. » Tue Aug 23, 2011 3:55 am

Honestly the game isn't that good... Which is too bad because I love this Batman cartoon, and as noted it's pretty as hell.

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Post by Stef » Tue Aug 23, 2011 8:08 am

We were talking from a technical point of view, and from this point, the game is just awesome. Also it has some very impressive sound tracks, one of the best on the sega genesis imo.
Beside that, the game is very difficult, and somewhat frustrating to play with...

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HardWareMan
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Post by HardWareMan » Tue Aug 23, 2011 9:53 am

I agree, this game often rise a "FFFFFUUUUU....." exception in my brain.

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King Of Chaos
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Post by King Of Chaos » Wed Aug 24, 2011 2:28 am

I must be one of the few people who actually enjoys this game. :D

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Post by Stef » Wed Aug 24, 2011 7:39 am

I do like this game, but again, somewhat frustrating as it's very difficult (at least for me).

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Shadow
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Post by Shadow » Wed Aug 24, 2011 2:33 pm


AamirM
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Post by AamirM » Sat Aug 27, 2011 4:18 pm

Thanks for the bug report :D. Will be fixed whenever I get the time.

Btw, yeah the game is hard. I used to use cheats on this game as well.

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