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lua/includes/extensions/math/ease.lua

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+--[[
+| This file was obtained through the combined efforts
+| of Madbluntz & Plymouth Antiquarian Society.
+|
+| Credits: lifestorm, Gregory Wayne Rossel JR.,
+| 	Maloy, DrPepper10 @ RIP, Atle!
+|
+| Visit for more: https://plymouth.thetwilightzone.ru/
+--]]
+
+module("math.ease", package.seeall)
+
+--[[---------------------------------------------------------
+	Source code of functions
+-----------------------------------------------------------]]
+
+-- https://github.com/Facepunch/garrysmod/pull/1755
+-- https://web.archive.org/web/20201212082306/https://easings.net/
+-- https://web.archive.org/web/20201218211606/https://raw.githubusercontent.com/ai/easings.net/master/src/easings.yml
+
+--[[---------------------------------------------------------
+	Easing constants
+-----------------------------------------------------------]]
+
+local c1 = 1.70158
+local c3 = c1 + 1
+local c2 = c1 * 1.525
+local c4 = ( 2 * math.pi ) / 3
+local c5 = ( 2 * math.pi ) / 4.5
+local n1 = 7.5625
+local d1 = 2.75
+
+--[[---------------------------------------------------------
+	To reduce _G lookups, we'll localize some commonly
+	used functions in this extension
+-----------------------------------------------------------]]
+
+local pi = math.pi
+local cos = math.cos
+local sin = math.sin
+local sqrt = math.sqrt
+
+--[[---------------------------------------------------------
+	Easing functions
+-----------------------------------------------------------]]
+
+function InSine( x )
+	return 1 - cos( ( x * pi ) / 2 )
+end
+
+function OutSine( x )
+	return sin( ( x * pi ) / 2 )
+end
+
+function InOutSine( x )
+	return -( cos( pi * x ) - 1 ) / 2
+end
+
+function InQuad( x )
+	return x ^ 2
+end
+
+function OutQuad( x )
+	return 1 - ( 1 - x ) * ( 1 - x )
+end
+
+function InOutQuad( x )
+	return x < 0.5 && 2 * x ^ 2 || 1 - ( ( -2 * x + 2 ) ^ 2 ) / 2
+end
+
+function InCubic( x )
+	return x ^ 3
+end
+
+function OutCubic( x )
+	return 1 - ( ( 1 - x ) ^ 3 )
+end
+
+function InOutCubic( x )
+	return x < 0.5 && 4 * x ^ 3 || 1 - ( ( -2 * x + 2 ) ^ 3 ) / 2
+end
+
+function InQuart( x )
+	return x ^ 4
+end
+
+function OutQuart( x )
+	return 1 - ( ( 1 - x ) ^ 4 )
+end
+
+function InOutQuart( x )
+	return x < 0.5 && 8 * x ^ 4 || 1 - ( ( -2 * x + 2 ) ^ 4 ) / 2
+end
+
+function InQuint( x )
+	return x ^ 5
+end
+
+function OutQuint( x )
+	return 1 - ( ( 1 - x ) ^ 5 )
+end
+
+function InOutQuint( x )
+	return x < 0.5 && 16 * x ^ 5 || 1 - ( ( -2 * x + 2 ) ^ 5 ) / 2
+end
+
+function InExpo( x )
+	return x == 0 && 0 || ( 2 ^ ( 10 * x - 10 ) )
+end
+
+function OutExpo( x )
+	return x == 1 && 1 || 1 - ( 2 ^ ( -10 * x ) )
+end
+
+function InOutExpo( x )
+	return x == 0
+		&& 0
+		|| x == 1
+		&& 1
+		|| x < 0.5 && ( 2 ^ ( 20 * x - 10 ) ) / 2
+		|| ( 2 - ( 2 ^ ( -20 * x + 10 ) ) ) / 2
+end
+
+function InCirc( x )
+	return 1 - sqrt( 1 - ( x ^ 2 ) )
+end
+
+function OutCirc( x )
+	return sqrt( 1 - ( ( x - 1 ) ^ 2 ) )
+end
+
+function InOutCirc( x )
+	return x < 0.5
+		&& ( 1 - sqrt( 1 - ( ( 2 * x ) ^ 2 ) ) ) / 2
+		|| ( sqrt( 1 - ( ( -2 * x + 2 ) ^ 2 ) ) + 1 ) / 2
+end
+
+function InBack( x )
+	return c3 * x ^ 3 - c1 * x ^ 2
+end
+
+function OutBack( x )
+	return 1 + c3 * ( ( x - 1 ) ^ 3 ) + c1 * ( ( x - 1 ) ^ 2 )
+end
+
+function InOutBack( x )
+	return x < 0.5
+		&& ( ( ( 2 * x ) ^ 2 ) * ( ( c2 + 1 ) * 2 * x - c2 ) ) / 2
+		|| ( ( ( 2 * x - 2 ) ^ 2 ) * ( ( c2 + 1 ) * ( x * 2 - 2 ) + c2 ) + 2 ) / 2
+end
+
+function InElastic( x )
+	return x == 0
+		&& 0
+		|| x == 1
+		&& 1
+		|| -( 2 ^ ( 10 * x - 10 ) ) * sin( ( x * 10 - 10.75 ) * c4 )
+end
+
+function OutElastic( x )
+	return x == 0
+		&& 0
+		|| x == 1
+		&& 1
+		|| ( 2 ^ ( -10 * x ) ) * sin( ( x * 10 - 0.75 ) * c4 ) + 1
+end
+
+function InOutElastic( x )
+	return x == 0
+		&& 0
+		|| x == 1
+		&& 1
+		|| x < 0.5
+		&& -( ( 2 ^ ( 20 * x - 10 ) ) * sin( ( 20 * x - 11.125 ) * c5 ) ) / 2
+		|| ( ( 2 ^ ( -20 * x + 10 ) ) * sin( ( 20 * x - 11.125 ) * c5 ) ) / 2 + 1
+end
+
+function InBounce( x )
+	return 1 - OutBounce( 1 - x )
+end
+
+function OutBounce( x )
+	if ( x < 1 / d1 ) then
+		return n1 * x ^ 2
+	elseif ( x < 2 / d1 ) then
+		x = x - ( 1.5 / d1 )
+		return n1 * x ^ 2 + 0.75
+	elseif ( x < 2.5 / d1 ) then
+		x = x - ( 2.25 / d1 )
+		return n1 * x ^ 2 + 0.9375
+	else
+		x = x - ( 2.625 / d1 )
+		return n1 * x ^ 2 + 0.984375
+	end
+end
+
+function InOutBounce( x )
+	return x < 0.5
+		&& ( 1 - OutBounce( 1 - 2 * x ) ) / 2
+		|| ( 1 + OutBounce( 2 * x - 1 ) ) / 2
+end