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Comos
Registered: May 2004
Posts: 73 |
Games that use VSP
Firts of all, I wanted to start this thread as a small research,coz during the years I encountered few game titles,that keeps crashing for a not well reason to me,but regarding VSP and especially VSP bug,that few years back was discovered seems it might have an explanation.
Here are titles, that Im aware of,that might use this technique,because of in game random crashes.
Creatures 1,Mayhem in Monsterland, Fred's Back 4
Creatures 1
Crashes mostly during starting of the game,when the screen scrolled horizontaly from right to left.Usually when I pass this, the game runs okay.
Mayhem in Monsterland
Besides, that the use of VSP is well known here I guess, this game crashes rarely during the character movement,atleast in my case.
Fred's Back 4 (Fred's in Troubles)
Maybe it's also related to whole Fred's Back series,but mostly I had problem with the last one.20 years ago,when I played this game, the game crashed for me everytime at the same level at the same place so I considered it as a bad swapper's copy.20 years later,when I wanted to try to finish the game,I tried again the AVT crack,that I had from the beginning,but a copy from csdb,but this time, the game crashed allmost immediately when the first level got loaded.I tested several other cracks,but had the same result.WTF?
The possibilities like kill cart,remove cart, remove everything have been considered,but still no luck.
Does anyone had similar issues or knows more games,that might crash? |
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Digger
Registered: Mar 2005
Posts: 427 |
Quote: Just for the record - VSP has to be updated every 8th line, right? :)
Nope. You only need to trigger it once :) You basically trick the VIC with changing $d011 on the right cycle, depending on the desired offset. Check out LFT's thread New VSP discovery |
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Hein
Registered: Apr 2004
Posts: 945 |
Only the first badline if it's full-screen. Not each badline. |
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Scan
Registered: Dec 2015
Posts: 111 |
@Jammer: No, only at the beginning of where you want to trigger the VSP effect. Only drawback is that 3 weird blocks appear which you need to mask out (in Insert Name Here I did it using an invalid graphics mode, but sprites could be used as well, I guess). Here's a screenshot of a work in progress phase. The three blocks could be masked black (the lower 4 bits of the next instruction after VSP triggering determine the color, a cpx #$00 would have it turned black). Unfortunately I also triggered redrawing the last line. Since I didn't know how to cope with it I decided to mask it out using the invalid graphics mode described above.)
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Jammer
Registered: Nov 2002
Posts: 1335 |
Thx guys! I was curious being rather unsuccessful with oneshot triggering myself ;) |
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JackAsser
Registered: Jun 2002
Posts: 2014 |
@scan: normally you'd line crunch away that first row of chars with a simple inc $d011 immediatly after the dec $d011 you did to start the vsp. Then mask the single line of pixels under the upper border |
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Count Zero
Registered: Jan 2003
Posts: 1926 |
Just to add to the examples above: Jim Slim +8FHP also uses VSP. |
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algorithm
Registered: May 2002
Posts: 705 |
Also Phobia by ratt used vsp. Great graphics, what a hard game it was however. |
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Hein
Registered: Apr 2004
Posts: 945 |
Quote: Also Phobia by ratt used vsp. Great graphics, what a hard game it was however.
Thanks for the tip, looks very cool. Hadn't seen it before. |
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Jammer
Registered: Nov 2002
Posts: 1335 |
Ok, I figured out it's 49/50th line where magic happens ;) |
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Oswald
Registered: Apr 2002
Posts: 5086 |
Quote: Only the first badline if it's full-screen. Not each badline.
afaik, VSP can only be done on an idle line, that is either top / bottom border, or tear yourself one with "fld".
caused me big headaches when I wanted a vsp also in the middle of the screen.
basically its a dec/inc d011 iirc, and the horizontal timing of it is where the first screen column should start (or offsetted if you want) around where the dec happens will be column 0. |
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