Easing

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

The most basic one, 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 Qeasingcurve-linear.png
InQuad Qeasingcurve-inquad.png
OutQuad Qeasingcurve-outquad.png
InOutQuad Qeasingcurve-inoutquad.png
OutInQuad Qeasingcurve-outinquad.png
InElastic Qeasingcurve-inelastic.png yesyesDue to elastic effect, this easing function produces some values < 0
OutElastic Qeasingcurve-outelastic.png yesyesDue to elastic effect, this easing function produces some values > 1
InOutElastic Qeasingcurve-inoutelastic.png yesyesDue to elastic effect, this easing function produces some values < 0 and > 1
OutInElastic Qeasingcurve-outinelastic.png yesyesDue to elastic effect, this easing function produces some values < 0 and > 1
InBack Qeasingcurve-inback.png yesDue to overshoot, this easing function produces some values < 0
OutBack Qeasingcurve-outback.png yesDue to overshoot, this easing function produces some values > 1
InOutBack Qeasingcurve-inoutback.png yesDue to overshoot, this easing function produces some values <0 and > 1
OutInBack Qeasingcurve-outinback.png yes
InBounce Qeasingcurve-inbounce.png yes
OutBounce Qeasingcurve-outbounce.png yes
InOutBounce Qeasingcurve-inoutbounce.png yes
OutInBounce Qeasingcurve-outinbounce.png yes
SineCurve Qeasingcurve-sincurve.png 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 Qeasingcurve-coscurve.png 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 or acceleration/deceleration changes). The pictures of the easing functions are directly extracted from Qt documentation, © 2008-2010 Nokia Corporation and/or its subsidiaries.