Vital.sandbox

util.easing.quad_in

Shared

Applies a quadratic ease-in — accelerates from zero using a squared curve


Syntax

local result = util.easing.quad_in(
    progress
)

Quad easing applies a second-degree polynomial curve.

  • Subtle and natural — noticeably smoother than Linear but less dramatic than Cubic.
  • Best for — general-purpose UI motion, button press feedback, and panel slides.

Parameters

TypeNameDescription
floatprogressInterpolation factor, typically in the range [0, 1]

Returns

TypeNameDescription
floatresultEased progress value

Examples

Sample output at key progress values
core.engine.print("info", util.easing.quad_in(0.0))  -- 0.0
core.engine.print("info", util.easing.quad_in(0.25)) -- near start
core.engine.print("info", util.easing.quad_in(0.5))  -- midpoint
core.engine.print("info", util.easing.quad_in(0.75)) -- near end
core.engine.print("info", util.easing.quad_in(1.0))  -- 1.0
Pair with lerp to animate a value
local result = util.easing.lerp(0, 100, util.easing.quad_in(0.5))

core.engine.print("info", result)
Animate a circle across the screen
local resolution = core.engine.get_resolution()
local duration = 1.5
local start_tick = core.engine.get_tick()

util.event.on("sandbox:draw", function()
    local elapsed = (core.engine.get_tick() - start_tick) / 1000.0
    local t = math.min(elapsed / duration, 1.0)
    local x = util.easing.lerp(0, resolution[1], util.easing.quad_in(t))

    core.engine.draw_circle({x, resolution[2]*0.5}, 16, {1, 1, 1, 1})
end)

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SyntaxParametersReturnsExamples