Parallel Universe: Difference between revisions

[[File:ParallelUniverseViews.jpg|thumb|A diagram of Parallel Universe movement in [[Hazy Maze Cave]], after [[Mario]] has returned to the main map.]]

A '''Parallel Universe''', or '''PU''', is a region of space located far outside the intended map boundaries that reflects certain aspects, especially the floors and/or ceilings, of the main map. When the game looks for floors below (or ceilings above) a given object, it first "truncates" the object's position from a floating point value to a 16-bit integer value. The range of a floating point value is much larger than the range of a 16-bit integer value (which is -2¹⁵ = -32,768 to 2¹⁵ - 1 = 32,767). If a coordinate of the object's position falls outside this range, it "wraps around". For example, if one of these floating point values is 40,000, then 40,000 - 65,536 = -25,536 will be used when determining if the object is aligned with a floor or ceiling. This gives the illusion that the floors and ceilings of the main level map are "copied" repeatedly in a uniform 3D grid, at a spacing of 65,536 units.

The truncation responsible for the existence of parallel universes is only performed when determining alignment with floors and ceilings. This means that walls and objects, both of which use floating point arithmetic to determine collision, do not "exist" in PUs, unless they are brought there.

Due to the extremely high speed required to travel to PUs, they are not accessible from all courses. The courses where PUs can or cannot be accessed are summarized in the tables below. Work is ongoing to try to access PUs in courses such as [[Bowser in the Fire Sea]] (via [[Bully battery]]) and demo courses (via massive [[Spawning displacement]]).

{|

|+

!Course

!PU Access

!Method

|-

|[[Bob-omb Battlefield]]

|Yes

|EBLJ

|-

|[[Whomp's Fortress]]

|Yes<ref>[https://www.youtube.com/watch?v=y_gELy37HHc "Going to a vertical PU in WF" by Maria Nicolae]</ref>

|No

|-

|[[Jolly Roger Bay]]

|Yes

|No

|HSW

|[[Cool, Cool Mountain]]

|No

|No

|

|-

|[[Big Boo's Haunt]]

|No

|EBLJ

|[[Hazy Maze Cave]]

|Yes

|Yes

|EBLJ, HSW

|[[Lethal Lava Land]]

|Yes

|Yes

|BB

|[[Shifting Sand Land]]

|Yes

|Yes

|EBLJ, HSP

|[[Dire, Dire Docks]]

|Yes

|No

|Pole Teleport

|[[Snowman's Land]]

|Yes

|No

|HSW

|-

|[[Wet-Dry World]]

|Yes

|EBLJ, HSW

|[[Tall, Tall Mountain]]

|No

|No

|

|[[Tiny-Huge Island]]

|No

|No

|

|[[Tick Tock Clock]]

|No

|No

|

|[[Rainbow Ride]]

|Yes

|No

|EBLJ

!Course

!PU Access

!Method

|-

|[[Bowser in the Dark World]]

|No

|No

|

|[[Bowser in the Fire Sea]]

|Yes

|No

|-

|[[Bowser in the Sky]]

|No

|No

|

|[[The Princess's Secret Slide]]

|No

|No

|

|[[Secret Aquarium]]

|No

|No

|

|[[Tower of the Wing Cap]]

|No

|No

|

|[[Cavern of the Metal Cap]]

|No

|No

|

|[[Vanish Cap under the Moat]]

|Yes

|No

|EBLJ

|[[Wing Mario over the Rainbow]]

|No

|No

|

|[[The Castle#Castle Grounds|Castle Grounds]]

|Yes

|Yes

|HSW, Speed Conservation

|[[The Castle#First Floor|Castle Foyer]]

|Yes

|Yes

|Speed Conservation

|[[The Castle#Basement|Castle Basement]]

|No

|No

|

|[[The Castle#Second Floor|Castle Upstairs]]

|No

|No

|

|-

|[[The Castle#Courtyard|Castle Courtyard]]

|No

|

|}

|}

Although usually the term "PU" refers to a horizontal PU (i.e. one caused by truncation of the ''x'' and/or ''z'' coordinates of an object's position), vertical PUs (where the ''y'' coordinate is truncated) also exist. However, these behave completely differently to horizontal PUs. While truncated coordinates are used to ''find'' the floor below the object and the ceiling above the object, the original floating point values are used to determine what ''effect'' these surfaces have on the object.

On the other hand, when Mario is below his "nearest" floor, he will snap up to it. This means that if Mario moves to a negative vertical PU, he will usually upwarp back to the main PU grid. This is called an '''overflow jump''', or '''OJ''' for short.

As traveling to PUs involves moving very far from the origin, floating point imprecision can begin to have a significant effect on Mario's position, angle, and collision. When Mario's position becomes large enough, this imprecision will result in the coordinates in PUs becoming so coarse that Mario cannot cross from one coordinate to the next and, eventually, will result in certain PUs being completely unaccessible.  

While in theory the grid of PUs extends indefinitely, the behavior of the truncation operation becomes "undefined" when the floating point value is outside the range -2³¹ to 2³¹ - 1. The Nintendo 64 and [[iQue]] Player<ref>[https://youtu.be/_dAGdYd9KUY "Do Parallel Universes Crash on iQue?" by CadBrad]</ref> versions of the game crash when such a truncation is attempted. The Wii and Wii U virtual console versions of the game do not crash, though it is not currently known whether they wrap around the 32-bit integer range, or cap to the endpoints of the range. Most emulators do not properly emulate the crash, except for a specific version of Mupen64, modded to crash correctly.

While not all conditions for these types of crashes are known, there are some that come up frequently. These are when:

Certain objects and graphics behave interestingly while in parallel universes. For example:

==References==

[[Category:Glitches]]

{{Glitches}}