Easing

Easing functions describe functions that control the way an interpolation between 0 and 1 is done.

The most basic easing function, linear, is just a linear interpolation at constant speed. Other more advanced easing functions can have acceleration at the beginning, the end or both or deceleration, or even bouncing or elastic effects.

Preliminary note

In the functions using easing, there are usually 3 optional parameters. Most functions don't need them at all, the ones needing one or more parameters are listed in the table below. When providing optional parameters, all the parameters before a given parameter must be filled, even if the easing function you intend to use doesn't require such a parameter. In this case, simply use 0 for the parameters you don't need. Examples:

• "Linear" can be used simply with getEasingValue( fProgress, "Linear" )
• "OutElastic" can define fEasingPeriod and fEasingAmplitude so it can be used with getEasingValue( fProgress, "OutElastic", 0.3, 1.0 )
• "InBack" can define fEasingOvershoot, but since it comes after fEasingPeriod and fEasingAmplitude in the order of parameters, 0 must be used for the others with getEasingValue( fProgress, "InBack", 0, 0, 1.7015 )

Easing functions

Default values are (when a function can use a parameter but it's not defined by the user):

• fEasingPeriod: 0.3
• fEasingAmplitude : 1.0
• fEasingOvershoot: 1.701

Easing function	Function profile	Uses fEasingPeriod	Uses fEasingAmplitude	Uses fEasingOvershoot	Comments
Linear
InQuad
OutQuad
InOutQuad
OutInQuad
InElastic		yes	yes		Due to the elastic effect, this easing function produces some values < 0
OutElastic		yes	yes		Due to the elastic effect, this easing function produces some values > 1
InOutElastic		yes	yes		Due to the elastic effect, this easing function produces some values < 0 and > 1
OutInElastic		yes	yes		Due to the elastic effect, this easing function produces some values < 0 and > 1
InBack				yes	Due to overshoot, this easing function produces some values < 0
OutBack				yes	Due to overshoot, this easing function produces some values > 1
InOutBack				yes	Due to overshoot, this easing function produces some values <0 and > 1
OutInBack				yes
InBounce			yes
OutBounce			yes
InOutBounce			yes
OutInBounce			yes
SineCurve					This easing function doesn't end at 1 but goes back to 0. In this case, for interpolation, the target value is just an edge but doesn't represent the stop value.
CosineCurve					This easing function both starts and stops at 0.5, going first to 1 then 0. In this case, for interpolation, the source and target values are just the edges but don't represent the start/stop values.

Source

The naming conventions of the functions below, available in moveObject, interpolateBetween, or getEasingValue have been extracted from Qt documentation. Only a subset of those functions is available in MTA since some of them are a bit redundant (only the profile of the acceleration/deceleration changes). The pictures of the easing functions are directly extracted from Qt documentation, © 2008-2010 Nokia Corporation and/or its subsidiaries.