Easing
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 |  |
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| InQuad |  |
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| OutQuad |  |
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| InOutQuad |  |
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| OutInQuad |  |
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| InElastic |  |
yes | yes | Due to elastic effect, this easing function produces some values < 0 | |
| OutElastic |  |
yes | yes | Due to elastic effect, this easing function produces some values > 1 | |
| InOutElastic |  |
yes | yes | Due to elastic effect, this easing function produces some values < 0 and > 1 | |
| OutInElastic |  |
yes | yes | Due to 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 or acceleration/deceleration changes). The pictures of the easing functions are directly extracted from Qt documentation, © 2008-2010 Nokia Corporation and/or its subsidiaries.