<function name="Lerp" parent="Global" type="libraryfunc"> <description> Performs a linear interpolation from the start number to the end number. This function provides a very efficient and easy way to smooth out movements. See also <page>math.ease</page> for functions that allow to have non linear animations using linear interpolation. <note>This function is not meant to be used with constant value in the first argument if you're dealing with animation! Use a value that changes over time. See example for **proper** usage of Lerp for animations.</note> </description> <realm>Shared and Menu</realm> <file line="261-L268">lua/includes/util.lua</file> <args> <arg name="t" type="number">The fraction for finding the result. This number is clamped between 0 and 1. Shouldn't be a constant.</arg> <arg name="from" type="number">The starting number. The result will be equal to this if delta is 0.</arg> <arg name="to" type="number">The ending number. The result will be equal to this if delta is 1.</arg> </args> <rets> <ret name="" type="number">The result of the linear interpolation, `from + (to - from) * t`.</ret> </rets> </function> <example> <description>Example of simple Lerp usage for animations.</description> <code> local start = SysTime()⤶ -- A variable to store the animation's start time is needed if you⤶ -- want to use the "Lerp" function to make timed animations.⤶ local animation_start, animation_duration = CurTime(), 2⤶ hook.Add( "HUDPaint", "LerpAnimation", function() draw.RoundedBox( 4, 100, 100, Lerp( SysTime() - start, 0, 100 ), 20, color_white )⤶ ⤶ if SysTime() - start > 2 then⤶ start = SysTime() -- "CurTime() - animation_start" is used to get the total elapsed time and then⤶ -- the elapsed time is divided by however long you want the animation to last.⤶ -- This gets the animation's progress as a number between 0 and 1, a fraction. local animation_progress = ( CurTime() - animation_start ) / animation_duration⤶ ⤶ -- The "Lerp" function is then called using the fraction as the first argument with⤶ -- the second being the value you want to start at ("from") when the fraction is "0" and⤶ -- the third being the final value ("to") when the fraction is "1".⤶ ⤶ -- If the "from" value is going to be "0" consider using the formula "to * animation_progress"⤶ -- This is a slightly faster method and will achieve the same result as if you were to use "Lerp".⤶ -- For example if you wanted to reverse this animation the line could be:⤶ -- "local animated_value = 255 * animation_progress"⤶ local animated_value = Lerp( animation_progress, 255, 0 )⤶ ⤶ -- In this case the "Lerp" function is being used to make a rect fade out.⤶ surface.SetDrawColor( 255, 255, 255, animated_value )⤶ surface.DrawRect( 50, 50, 300, 300 )⤶ ⤶ -- If you add the start time and duration together you'll have the total⤶ -- animation time, and if you compare it to the current time you can check⤶ -- if the animation has completed.⤶ ⤶ -- A slightly more optimised way of checking if the animation has completed is by checking⤶ -- if the "animation_progress" is equal to "1" or if "animated_value" is equal to the third⤶ -- argument used when "Lerp" was called.⤶ if ( animation_start + animation_duration <= CurTime() ) then⤶ -- In this example we're just resetting the start time when the animation completes.⤶ animation_start = CurTime()⤶ end end ) </code> </example> <example> <description>Advanced example of Lerp animation: A health bar that will smooth the health change over 0.5 seconds to reach new health value from the previous value.</description> <code> local start, oldhp, newhp = 0, -1, -1 local barW = 200 local animationTime = 0.5 -- seconds hook.Add( "HUDPaint", "LerpAnimation", function() -- Local player still loading, do nothing if ( !IsValid( LocalPlayer() ) ) then return end local hp = LocalPlayer():Health() local maxhp = LocalPlayer():GetMaxHealth() -- The values are not initialized yet, do so right now if ( oldhp == -1 and newhp == -1 ) then oldhp = hp newhp = hp end -- You can use a different smoothing function here local smoothHP = Lerp( ( SysTime() - start ) / animationTime, oldhp, newhp ) -- Health was changed, initialize the animation if newhp ~= hp then -- Old animation is still in progress, adjust if ( smoothHP ~= hp ) then -- Pretend our current "smooth" position was the target so the animation will -- not jump to the old target and start to the new target from there newhp = smoothHP end oldhp = newhp start = SysTime() newhp = hp end draw.RoundedBox( 4, 100, 200, barW, 100, color_black ) draw.RoundedBox( 4, 100, 200, math.max( 0, smoothHP ) / maxhp * barW, 100, color_white ) end ) </code> </example>