GetEasingValue

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Used for custom Lua based interpolation, returns the easing value (animation time to use in your custom interpolation) given a progress and an easing function. In most cases, either moveObject or interpolateBetween can do the job. getEasingValue is only provided in case you want to do your own custom interpolation based on easing.

Syntax

float getEasingValue( float fProgress, string strEasingType [, float fEasingPeriod, float fEasingAmplitude, float fEasingOvershoot] )

Required Arguments

  • fProgress: float between 0 and 1 indicating the interpolation progress (0 at the beginning of the interpolation, 1 at the end).
  • strEasingType: the easing function to use for the interpolation

Optional Arguments

  • fEasingPeriod: the period of the easing function (only some easing functions use this parameter)
  • fEasingAmplitude: the amplitude of the easing function (only some easing functions use this parameter)
  • fEasingOvershoot: the overshoot of the easing function (only some easing functions use this parameter)

Returns

Returns fAnimationTime the animation time given by the easing function (can be < 0 or > 1 since some easing functions have overshoot or bounce/spring effects, false otherwise (error in parameters).

Example

The examples below are only clientside ones, even though the functions can be used on both sides. Indeed it makes more sense to use them with onClientRender/onClientPreRender but the freedom is given to use it in any other context.

Click to collapse [-]
Client

This clientside example uses getEasingValue to make a custom camera fade. The command to test it is "/fade". The fading out is done with "InQuad" to have a slow fading which then accelerates and "OutQuad" is used for fading in to have a smooth end of the fading. In this example interpolateBetween could have been used directly to interpolate the alpha between 0 and 255 and then 255 and 0 but is example is just to illustrate the use of getEasingValue by itself.

local g_Fade = nil
addCommandHandler("fade", 
function ()
	if g_Fade then return end
	g_Fade = {}
	g_Fade.startTime = getTickCount()
	g_Fade.endTime = g_Fade.startTime + 2000
	g_Fade.easingFunction = "InQuad" --Slow at first and accelerating
	addEventHandler("onClientRender", getRootElement(), fadeCameraOut)
end)

function fadeCameraOut()
	local now = getTickCount()
	local elapsedTime = now - g_Fade.startTime
	local duration = g_Fade.endTime - g_Fade.startTime
	local progress = elapsedTime / duration
	
	local fAnimationTime = getEasingValue(progress, g_Fade.easingFunction)
	
	local alpha = fAnimationTime*255
	local width, height = guiGetScreenSize()
	dxDrawRectangle(0, 0, width, height, tocolor(0, 0, 0, alpha), true)
	
	if now > g_Fade.endTime then
		removeEventHandler("onClientRender", getRootElement(), fadeCameraOut)
		g_Fade.startTime = getTickCount()
		g_Fade.endTime = g_Fade.startTime + 2000
		g_Fade.easingFunction = "OutQuad" --Fast at first then decelerating
		addEventHandler("onClientRender", getRootElement(), fadeCameraIn)
	end
end

function fadeCameraIn()
	local now = getTickCount()
	local elapsedTime = now - g_Fade.startTime
	local duration = g_Fade.endTime - g_Fade.startTime
	local progress = elapsedTime / duration
	
	local fAnimationTime = getEasingValue(progress, g_Fade.easingFunction)
	
	local alpha = (1-fAnimationTime)*255
	local width, height = guiGetScreenSize()
	dxDrawRectangle(0, 0, width, height, tocolor(0, 0, 0, alpha), true)
		
	if now > g_Fade.endTime then
		removeEventHandler("onClientRender", getRootElement(), fadeCameraIn)
		g_Fade = nil
	end
end

See Also