Introduction

AIR is a text file format that describes a set of animations. The AIR format is used widely throughout M.U.G.E.N for animating characters, backgrounds, life bars and more.

An animation (specifically called an animation action in M.U.G.E.N) describes a single sequence of sprites to display. A character's animation file (.air) can contain as many animation actions as necessary.

The format

Here's a typical entry from an .air file. We will explain the format next.

; Standing Animation
[Begin Action 000]
Clsn2Default: 2
 Clsn2[0] = -10,  0, 10,-79
 Clsn2[1] =  -4,-92,  6,-79
0,1, 0,0, 7
0,2, 0,0, 7
0,3, 0,0, 7
0,4, 0,0, 50
0,5, 0,0, 7
0,6, 0,0, 7
0,7, 0,0, 7
0,8, 0,0, 60

Semicolon (;) is used for comments. They can be used anywhere and everything after the semicolon on the same line is ignored.

[Begin Action n]

This defines an action. The number n is called the action number. Each action must have a unique action number in order to be distinguishable from other actions. You can have many actions, but keep in mind that there are reserved actions numbers. These numbers and their associated actions are listed below.

Clsn2Default: 2

This says that there are two collision boxes being defined and they will be defined for all the entries below the Clsn definition. In this case for every sprite in this action. If you don't want to have a default collision box, then change Clsn2Default to Clsn2. You must put the Clsn definition before a sprite entry. Each sprite entry can have its own collision boxes. Clsn2 refers to a plain collision box and Clsn1 refers to an "attacking" box. You use attacking boxes when making attacking actions such as punching and kicking or special moves. To define collision boxes, use AirEdit, a program included in the M.U.G.E.N development toolset.

0,3, 0,0, 7

An entry looking like this is called an "animation element", or just "element" for short. 1st number is the sprite's group number. 2nd number is the sprite's image number. You assign these numbers to your sprites when you make an .sff file.

So group #0 and image #3 were defined with sprmaker with an entry such as 0,3, mypic.png, 40, 40.

The 3rd and 4th numbers of the element represent the X and Y offsets to the sprite's position. For example, the pair 15,-10 would shift the sprite's position 15 pixels forwards and 10 pixels upwards. This offset is affected by scaling operations but not rotation.

5th number is the length of time to display the element before moving onto the next, measured in game-ticks. There are 60 game-ticks in one second at normal game speed. For the 5th number, you can specify "-1" if you want that element to be displayed indefinitely (or until you switch to a different action). If you choose to do this, do it only on the last element of the action.

The "looptime" of an action is the sum of all the times of each element. Basically, it is the total length of the action in game-ticks. If the last element has a time of "-1", the looptime will be considered infinite. We call that "no loop". Actions with a finite loop time will go back to the first element after it has finished displaying the last element, and keep looping until the you switch to another action.

In the example action above, the looptime would be: 7 + 7 + 7 + 50 + 7 + 7 + 7 + 60 = 152 ticks

; Standing Animation
[Begin Action 000]
Clsn2Default: 2
 Clsn2[0] = -10,  0, 10,-79
 Clsn2[1] =  -4,-92,  6,-79
0,1, 0,0, 7
0,2, 0,0, 7
Loopstart
0,3, 0,0, 7
0,4, 0,0, 50
0,5, 0,0, 7
0,6, 0,0, 7
0,7, 0,0, 7
0,8, 0,0, 60

Adding a line with the word Loopstart will make the animation begin looping from the element on the following line. In the example above, when the element with sprite 0,8 is displayed, the next element to be shown will be the one with sprite 0,3.

When testing out your animations, you may find the pause and frame-advance functions useful. To pause, hit the "Pause" button. To advance the game by one game-tick, press Scroll Lock. Frame- advance only works when the game is paused.

15,1, 0,0, 5

15,1, 0,0, 5, H   ;<-- This flips it horizonally
15,2, 0,0, 5, V   ;<-- This flips it vertically
15,3, 0,0, 5, VH  ;<-- This flips it both ways, ie. rotates 180 deg

15,4, 0,0, 5, ,A   ;<-- Color addition (flip parameter omitted)
15,4, 0,0, 5, H, S ;<-- Flips horizontally and does color subtraction

15,4, 0,0, 5, ,A1  ;<-- Color addition to 50% darkened dest
15,4, 0,0, 5, ,AS128D128 ;<-- Mix 50% source with 50% dest

15,4, 0,0, 5, ,A, 1.5,2

15,4, 0,0, 5, ,A, 1,1, 45

Interpolate <type>

Interpolate Offset
Interpolate Scale
20,0, 0,0, 60, , , 1,1
Interpolate Offset
Interpolate Scale
20,0, 100,0, 60, , , 1.5,1.5

20,0, 0,0, 59, , , 1,1, 0
Interpolate Angle
20,0, 0,0, 1, , , 1,1, 354

Character Reserved Action Numbers

M.U.G.E.N's common state engine (data/common1.cns) requires several animation actions to be present in your character (a warning will be logged if not all required animations are present). There are also some actions that are optional, which will be made use of if present in your character.

If you are unsure of how any of these actions should look, take a look at chars/kfm/kfm.air.

All action numbers in the 5000-5999 range not listed below are reserved for possible future use, so avoid using those numbers for custom actions.

An "opt" besides the number means the animation is optional.

Optional Hit Up animations (see Note 5):

Optional Hit Up-Diagonal animations (see Note 6):

Note 1: These do not actually have to use only the stated numbers. If is

more of a recommended number than a M.U.G.E.N one. If necessary, feel free to use any other action numbers.

Note 2: If medium and heavy hits are omitted, they default to the light hits

Note 3: "No loop" means last frame has a time of -1.

For recover animation, the first frame of each recovery should be the last frame of the corresponding hit. Eg. If action 5000 has frame 5000,0 and 5000,1, then action 5005 should start with frame 5000,1. This is because the animation will be locked in the first frame of the recovery after the hit animation is over, but before the player has recovered from the hit. If you have a Stand/Air Hit transition animation, then the first frame of Air Recover and Air Fall should be the last frame of the transition animation.

Note 4: The Stand/Air Hit transition animation is played back after each

hit animation in (or into) the air, but before the Air Recover and Air Fall animations.

Note 5: You can loop the LieDown Hit if you want the player to look like he

is "twitching" while being hit

Note 6: This set of animations is optional. It is an alternate set of

falling animations, which is used if hit by a HitDef with "Up" as the animtype.

Note 7: This set of animations is optional. It is an alternate set of

falling animations, which is used if hit by a HitDef with "DiagUp" as the animtype.

Recommended Action Numbers

You do not have to follow this exactly, but it should serve as a guideline. In general, the states in the CNS should have the same numbers as the animation they use, to reduce confusion.

You might want space out your animation and state numbers. This gives room for you to add in more actions as necessary (some attacks can use multiple states and animations). For instance, Standing Light Kick and Standing Strong Kick could have action numbers 200 and 210 respectively.