Negative BPM's

[Emo-Gaara_14]

How do you use negative BPM's in StepMania 3.9? I don't understand them all that well! I know how to set them but I just don't understand how to know where they will end up at! For example: The Family Farce song things have a lot of those sometimes! I just want to understand how to use them!

[PlasmaFire]

Negative BPMs tracks are nothing new, but are plenty interesting...they let you skip measures so that notes can suddenly show up half-way, a quarter of the way, or even less up the screen. The Hopscotch (Tsu) series by Family Farce is a good example of when using it can make SM rather fun to play.

I can't explain this easily, but I'll try to describe the simplest method of implementing a negative BPM (what I'd like to call "reflecting") trick. This method will let you skip a certain number of measures depending on the value of the negative and positive BPMs that "bound" the area on the simfile that you don't want people to actually play.

I'll use a video of one of my simfiles as an example: "Cha Cha Cha" - http://youtube.com/watch?v=__hY349TrkE

This simfile initially runs at exactly 106 BPM (on the quarter notes) once the music begins. Carefully watch the video and observe what happens for the first two negative BPM jumps.

The following is a screenshot of the stepchart (using ITGFreak.com's stepchart viewer); this is the portion you just watched, with a little bit of the "normal BPM" stepchart in the bottom half of the second-to-rightmost column as well as the rightmost column itself. Note that the massive BPM slowdown at the beginning is just a trick to fool the player into thinking that this chart runs at 600613 BPM (get it? Google? :p).

How to read this image: the simfile screenshot's measures are divided into columns, each with a pattern of white, light grey, white, and dark grey bars in each column. Each bar is a quater of the beat; since StepMania assumes a song runs at 4/4 time signature, the shade pattern will repeat this way.



Note that the original stepchart screenshot does not have those green and red boxes nor the thick blue lines. They're MSPainted in explain what happens:

* The simfile starts playing normally after the initial pause of 3.44 seconds. It runs at 106 BPM at 4/4 time; synced to the song, this means that the chart passes one measure bar per four beats, or four measure bars for sixteen beats. I call this the "normal BPM" part, which is bounded by green boxes.

* When the track runs into the first negative BPM change (where it goes from +106 to -106), the program will suddenly try to play the chart backwards. If you tried to make a simfile that had a negative BPM to it somewhere in the chart, StepMania would literally play the stepchart backwards.

* The trick here is to implement a positive BPM somewhere after it so that you can "skip" the proper number of measures. Notice that the first change from -106 to +106 happens exactly four beats later--where the thick blue line is.

* With negative BPMs, you'd think that as soon as it switches from -106 to +106, the jump has ended. However, that's not the case! In fact, you need to track down another four beats before the negative BPM zone has ended. Therefore, everything in the red boxes is SKIPPED during the jump; the yellow holds preceded by mines, the four single notes, and the three single rows of mines are not played.

* Once the eight beats are skipped, the chart immediately resumes at +106 BPM in the green box (third column from the right)

* I added in another 106 BPM after the run to emphasize (as a note to myself) that this track will once again run at the original speed after the eight-beat jump; you can change this value so that the player experiences a sudden BPM slowdown/speedup in addition to the just-encountered jump.

* The next negative BPM change occurs four beats later; this time, when the -106 is encountered, the huge stack of mines is skipped; notice again how it is eight beats' worth of mines.

So why did I call this a "reflecting" negative BPM trick? It's because an equal number of measures before and after the change from a negative BPM to a positive BPM is skipped. Since this chart elapses four beats per measure, a 106 --> -106 --> 106 change will skip a total of eight beats.

There are more complex ways of implementing negative BPMs, including using different BPM changes that skip non-reflected numbers of beats. I can't quite explain that right now; however, you're welcome to take a look at the entire Cha Cha Cha stepchart and see where portions of the song are skipped:

http://www.uploadgeek.com/uploads456...ChaChaFull.png

[kurisu]

Negs are an exploit of a flaw in the 3.9 code that need never be used. They are broken in edit data, and cause a problem to where notes placed in the jump can never be hit, making it impossible to get 100% on a song.

Flawed, gimickey, and just plain broken, IMO.

[henke37]

Not to mention that they violate the trust the player has in the game to not lie.
If it is impossible to beat a song at the first try with max score, something is wrong.

[kurisu]

Not to mention that they violate the trust the player has in the game to not lie.
If it is impossible to beat a song at the first try with max score, something is wrong.

Well in the case of negs, it is impossible to clear a song with max score (well, DP score anyway).

Thats a good way to put it, too.. that it violates the trust... i mean, your supposed to do what is displayed. that simple. having basicly phantom arrows... well.. kills the game.

[PlasmaFire]

Thats a good way to put it, too.. that it violates the trust... i mean, your supposed to do what is displayed. that simple. having basicly phantom arrows... well.. kills the game.

Eh, I sort of disagree on that; I know it's a bug in the game, but when exploited properly with the right kind of music, negative BPMs are great (the Family Farce Hopscotch series is fun because of that, IMHO). Of course, overuse lends itself to serious challenge...or annoyance--especially when the jump ends on a beat containing a note (you can see some of that in the video I linked in the previous reply).

Also, it's entirely possible to create such a simfile that does not prevent people from scoring 100% on; the only requirement is that during a negative BPM zone, no notes are jumped--only blank space and mines. If the player knows that the song has these areas, it can create a sense of uneasiness when notes suddenly pop up a fraction of the way up the screen with no mods on. I like that sort of awkwardness when done right, and it promotes learning unexpected patterns.

[kurisu]

Thats a good way to put it, too.. that it violates the trust... i mean, your supposed to do what is displayed. that simple. having basicly phantom arrows... well.. kills the game.

Eh, I sort of disagree on that; I know it's a bug in the game, but when exploited properly with the right kind of music, negative BPMs are great (the Family Farce Hopscotch series is fun because of that, IMHO). Of course, overuse lends itself to serious challenge...or annoyance--especially when the jump ends on a beat containing a note (you can see some of that in the video I linked in the previous reply).

Also, it's entirely possible to create such a simfile that does not prevent people from scoring 100% on; the only requirement is that during a negative BPM zone, no notes are jumped--only blank space and mines. If the player knows that the song has these areas, it can create a sense of uneasiness when notes suddenly pop up a fraction of the way up the screen with no mods on. I like that sort of awkwardness when done right, and it promotes learning unexpected patterns.

But no one ever does this...

And again, with them not working correctly when C mods are used, and being TOTALY broken in edit data, they should NEVER be used. That simple.

[jeffrey1790]

what are simfiles?

[Emo-Gaara_14]

what are simfiles?

are you kiddin'?

simfiles are the steps you make for a song using the Edit/Sync button on the main menu...

are you kiddin'?

[shakesoda]

of course he was kidding.

to start, look at his site.