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/*
* Copyright (C) 2013 Apple Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
* THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
* THE POSSIBILITY OF SUCH DAMAGE.
*/
WI.SpringTimingFunction = class SpringTimingFunction
{
constructor(mass, stiffness, damping, initialVelocity)
{
this.mass = Math.max(1, mass);
this.stiffness = Math.max(1, stiffness);
this.damping = Math.max(0, damping);
this.initialVelocity = initialVelocity;
}
// Static
static fromValues(values)
{
if (!values || values.length < 4)
return null;
values = values.map(Number);
if (values.includes(NaN))
return null;
return new WI.SpringTimingFunction(...values);
}
static fromString(text)
{
if (!text || !text.length)
return null;
let trimmedText = text.toLowerCase().trim();
if (!trimmedText.length)
return null;
let matches = trimmedText.match(/^spring\(([\d.]+)\s+([\d.]+)\s+([\d.]+)\s+([-\d.]+)\)$/);
if (!matches)
return null;
return WI.SpringTimingFunction.fromValues(matches.slice(1));
}
// Public
copy()
{
return new WI.SpringTimingFunction(this.mass, this.stiffness, this.damping, this.initialVelocity);
}
toString()
{
return `spring(${this.mass} ${this.stiffness} ${this.damping} ${this.initialVelocity})`;
}
solve(t)
{
let w0 = Math.sqrt(this.stiffness / this.mass);
let zeta = this.damping / (2 * Math.sqrt(this.stiffness * this.mass));
let wd = 0;
let A = 1;
let B = -this.initialVelocity + w0;
if (zeta < 1) {
// Under-damped.
wd = w0 * Math.sqrt(1 - zeta * zeta);
A = 1;
B = (zeta * w0 + -this.initialVelocity) / wd;
}
if (zeta < 1) // Under-damped
t = Math.exp(-t * zeta * w0) * (A * Math.cos(wd * t) + B * Math.sin(wd * t));
else // Critically damped (ignoring over-damped case).
t = (A + B * t) * Math.exp(-t * w0);
return 1 - t; // Map range from [1..0] to [0..1].
}
calculateDuration(epsilon)
{
epsilon = epsilon || 0.0001;
let t = 0;
let current = 0;
let minimum = Number.POSITIVE_INFINITY;
while (current >= epsilon || minimum >= epsilon) {
current = Math.abs(1 - this.solve(t)); // Undo the range mapping
if (minimum < epsilon && current >= epsilon)
minimum = Number.POSITIVE_INFINITY; // Spring reversed direction
else if (current < minimum)
minimum = current;
t += 0.1;
}
return t;
}
};
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