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	It was Godot-ified and integrated into Tween originally (#628) without mention that it was thirdparty code, but it's actually derived from https://github.com/jesusgollonet/ofpennereasing. It's also very bad quality code and should be replaced by a better, properly-maintained library of easing equations.
		
			
				
	
	
		
			308 lines
		
	
	
	
		
			10 KiB
		
	
	
	
		
			C++
		
	
	
	
	
	
			
		
		
	
	
			308 lines
		
	
	
	
		
			10 KiB
		
	
	
	
		
			C++
		
	
	
	
	
	
/**
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 *  Adapted from Penner Easing equations' C++ port.
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 *  Source: https://github.com/jesusgollonet/ofpennereasing
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 *  License: BSD-3-clause
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 */
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#include "scene/animation/tween.h"
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const real_t pi = 3.1415926535898;
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///////////////////////////////////////////////////////////////////////////
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// linear
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///////////////////////////////////////////////////////////////////////////
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namespace linear {
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static real_t in(real_t t, real_t b, real_t c, real_t d) {
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	return c * t / d + b;
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}
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static real_t out(real_t t, real_t b, real_t c, real_t d) {
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	return c * t / d + b;
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}
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static real_t in_out(real_t t, real_t b, real_t c, real_t d) {
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	return c * t / d + b;
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}
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static real_t out_in(real_t t, real_t b, real_t c, real_t d) {
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	return c * t / d + b;
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}
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}; // namespace linear
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///////////////////////////////////////////////////////////////////////////
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// sine
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///////////////////////////////////////////////////////////////////////////
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namespace sine {
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static real_t in(real_t t, real_t b, real_t c, real_t d) {
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	return -c * cos(t / d * (pi / 2)) + c + b;
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}
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static real_t out(real_t t, real_t b, real_t c, real_t d) {
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	return c * sin(t / d * (pi / 2)) + b;
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}
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static real_t in_out(real_t t, real_t b, real_t c, real_t d) {
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	return -c / 2 * (cos(pi * t / d) - 1) + b;
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}
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static real_t out_in(real_t t, real_t b, real_t c, real_t d) {
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	return (t < d / 2) ? out(t * 2, b, c / 2, d) : in((t * 2) - d, b + c / 2, c / 2, d);
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}
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}; // namespace sine
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///////////////////////////////////////////////////////////////////////////
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// quint
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///////////////////////////////////////////////////////////////////////////
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namespace quint {
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static real_t in(real_t t, real_t b, real_t c, real_t d) {
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	return c * pow(t / d, 5) + b;
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}
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static real_t out(real_t t, real_t b, real_t c, real_t d) {
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	return c * (pow(t / d - 1, 5) + 1) + b;
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}
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static real_t in_out(real_t t, real_t b, real_t c, real_t d) {
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	t = t / d * 2;
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	if (t < 1) return c / 2 * pow(t, 5) + b;
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	return c / 2 * (pow(t - 2, 5) + 2) + b;
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}
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static real_t out_in(real_t t, real_t b, real_t c, real_t d) {
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	return (t < d / 2) ? out(t * 2, b, c / 2, d) : in((t * 2) - d, b + c / 2, c / 2, d);
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}
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}; // namespace quint
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///////////////////////////////////////////////////////////////////////////
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// quart
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///////////////////////////////////////////////////////////////////////////
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namespace quart {
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static real_t in(real_t t, real_t b, real_t c, real_t d) {
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	return c * pow(t / d, 4) + b;
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}
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static real_t out(real_t t, real_t b, real_t c, real_t d) {
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	return -c * (pow(t / d - 1, 4) - 1) + b;
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}
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static real_t in_out(real_t t, real_t b, real_t c, real_t d) {
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	t = t / d * 2;
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	if (t < 1) return c / 2 * pow(t, 4) + b;
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	return -c / 2 * (pow(t - 2, 4) - 2) + b;
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}
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static real_t out_in(real_t t, real_t b, real_t c, real_t d) {
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	return (t < d / 2) ? out(t * 2, b, c / 2, d) : in((t * 2) - d, b + c / 2, c / 2, d);
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}
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}; // namespace quart
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///////////////////////////////////////////////////////////////////////////
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// quad
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///////////////////////////////////////////////////////////////////////////
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namespace quad {
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static real_t in(real_t t, real_t b, real_t c, real_t d) {
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	return c * pow(t / d, 2) + b;
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}
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static real_t out(real_t t, real_t b, real_t c, real_t d) {
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	t = t / d;
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	return -c * t * (t - 2) + b;
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}
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static real_t in_out(real_t t, real_t b, real_t c, real_t d) {
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	t = t / d * 2;
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	if (t < 1) return c / 2 * pow(t, 2) + b;
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	return -c / 2 * ((t - 1) * (t - 3) - 1) + b;
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}
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static real_t out_in(real_t t, real_t b, real_t c, real_t d) {
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	return (t < d / 2) ? out(t * 2, b, c / 2, d) : in((t * 2) - d, b + c / 2, c / 2, d);
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}
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}; // namespace quad
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///////////////////////////////////////////////////////////////////////////
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// expo
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///////////////////////////////////////////////////////////////////////////
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namespace expo {
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static real_t in(real_t t, real_t b, real_t c, real_t d) {
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	if (t == 0) return b;
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	return c * pow(2, 10 * (t / d - 1)) + b - c * 0.001;
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}
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static real_t out(real_t t, real_t b, real_t c, real_t d) {
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	if (t == d) return b + c;
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	return c * 1.001 * (-pow(2, -10 * t / d) + 1) + b;
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}
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static real_t in_out(real_t t, real_t b, real_t c, real_t d) {
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	if (t == 0) return b;
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	if (t == d) return b + c;
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	t = t / d * 2;
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	if (t < 1) return c / 2 * pow(2, 10 * (t - 1)) + b - c * 0.0005;
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	return c / 2 * 1.0005 * (-pow(2, -10 * (t - 1)) + 2) + b;
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}
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static real_t out_in(real_t t, real_t b, real_t c, real_t d) {
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	return (t < d / 2) ? out(t * 2, b, c / 2, d) : in((t * 2) - d, b + c / 2, c / 2, d);
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}
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}; // namespace expo
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///////////////////////////////////////////////////////////////////////////
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// elastic
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///////////////////////////////////////////////////////////////////////////
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namespace elastic {
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static real_t in(real_t t, real_t b, real_t c, real_t d) {
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	if (t == 0) return b;
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	if ((t /= d) == 1) return b + c;
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	float p = d * 0.3f;
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	float a = c;
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	float s = p / 4;
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	float postFix = a * pow(2, 10 * (t -= 1)); // this is a fix, again, with post-increment operators
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	return -(postFix * sin((t * d - s) * (2 * pi) / p)) + b;
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}
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static real_t out(real_t t, real_t b, real_t c, real_t d) {
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	if (t == 0) return b;
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	if ((t /= d) == 1) return b + c;
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	float p = d * 0.3f;
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	float a = c;
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	float s = p / 4;
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	return (a * pow(2, -10 * t) * sin((t * d - s) * (2 * pi) / p) + c + b);
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}
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static real_t in_out(real_t t, real_t b, real_t c, real_t d) {
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	if (t == 0) return b;
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	if ((t /= d / 2) == 2) return b + c;
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	float p = d * (0.3f * 1.5f);
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	float a = c;
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	float s = p / 4;
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	if (t < 1) {
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		float postFix = a * pow(2, 10 * (t -= 1)); // postIncrement is evil
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		return -0.5f * (postFix * sin((t * d - s) * (2 * pi) / p)) + b;
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	}
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	float postFix = a * pow(2, -10 * (t -= 1)); // postIncrement is evil
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	return postFix * sin((t * d - s) * (2 * pi) / p) * 0.5f + c + b;
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}
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static real_t out_in(real_t t, real_t b, real_t c, real_t d) {
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	return (t < d / 2) ? out(t * 2, b, c / 2, d) : in((t * 2) - d, b + c / 2, c / 2, d);
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}
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}; // namespace elastic
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///////////////////////////////////////////////////////////////////////////
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// cubic
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///////////////////////////////////////////////////////////////////////////
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namespace cubic {
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static real_t in(real_t t, real_t b, real_t c, real_t d) {
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	return c * (t /= d) * t * t + b;
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}
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static real_t out(real_t t, real_t b, real_t c, real_t d) {
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	t = t / d - 1;
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	return c * (t * t * t + 1) + b;
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}
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static real_t in_out(real_t t, real_t b, real_t c, real_t d) {
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	if ((t /= d / 2) < 1) return c / 2 * t * t * t + b;
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	return c / 2 * ((t -= 2) * t * t + 2) + b;
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}
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static real_t out_in(real_t t, real_t b, real_t c, real_t d) {
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	return (t < d / 2) ? out(t * 2, b, c / 2, d) : in((t * 2) - d, b + c / 2, c / 2, d);
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}
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}; // namespace cubic
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///////////////////////////////////////////////////////////////////////////
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// circ
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///////////////////////////////////////////////////////////////////////////
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namespace circ {
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static real_t in(real_t t, real_t b, real_t c, real_t d) {
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	return -c * (sqrt(1 - (t /= d) * t) - 1) + b; // TODO: ehrich: operation with t is undefined
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}
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static real_t out(real_t t, real_t b, real_t c, real_t d) {
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	return c * sqrt(1 - (t = t / d - 1) * t) + b; // TODO: ehrich: operation with t is undefined
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}
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static real_t in_out(real_t t, real_t b, real_t c, real_t d) {
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	if ((t /= d / 2) < 1) return -c / 2 * (sqrt(1 - t * t) - 1) + b;
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	return c / 2 * (sqrt(1 - t * (t -= 2)) + 1) + b; // TODO: ehrich: operation with t is undefined
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}
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static real_t out_in(real_t t, real_t b, real_t c, real_t d) {
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	return (t < d / 2) ? out(t * 2, b, c / 2, d) : in((t * 2) - d, b + c / 2, c / 2, d);
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}
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}; // namespace circ
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///////////////////////////////////////////////////////////////////////////
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// bounce
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///////////////////////////////////////////////////////////////////////////
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namespace bounce {
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static real_t out(real_t t, real_t b, real_t c, real_t d);
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static real_t in(real_t t, real_t b, real_t c, real_t d) {
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	return c - out(d - t, 0, c, d) + b;
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}
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static real_t out(real_t t, real_t b, real_t c, real_t d) {
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	if ((t /= d) < (1 / 2.75f)) {
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		return c * (7.5625f * t * t) + b;
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	} else if (t < (2 / 2.75f)) {
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		float postFix = t -= (1.5f / 2.75f);
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		return c * (7.5625f * (postFix)*t + .75f) + b;
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	} else if (t < (2.5 / 2.75)) {
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		float postFix = t -= (2.25f / 2.75f);
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		return c * (7.5625f * (postFix)*t + .9375f) + b;
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	} else {
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		float postFix = t -= (2.625f / 2.75f);
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		return c * (7.5625f * (postFix)*t + .984375f) + b;
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	}
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}
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static real_t in_out(real_t t, real_t b, real_t c, real_t d) {
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	return (t < d / 2) ? in(t * 2, b, c / 2, d) : out((t * 2) - d, b + c / 2, c / 2, d);
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}
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static real_t out_in(real_t t, real_t b, real_t c, real_t d) {
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	return (t < d / 2) ? out(t * 2, b, c / 2, d) : in((t * 2) - d, b + c / 2, c / 2, d);
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}
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}; // namespace bounce
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///////////////////////////////////////////////////////////////////////////
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// back
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///////////////////////////////////////////////////////////////////////////
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namespace back {
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static real_t in(real_t t, real_t b, real_t c, real_t d) {
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	float s = 1.70158f;
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	float postFix = t /= d;
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	return c * (postFix)*t * ((s + 1) * t - s) + b;
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}
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static real_t out(real_t t, real_t b, real_t c, real_t d) {
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	float s = 1.70158f;
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	return c * ((t = t / d - 1) * t * ((s + 1) * t + s) + 1) + b; // TODO: ehrich: operation with t is undefined
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}
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static real_t in_out(real_t t, real_t b, real_t c, real_t d) {
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	float s = 1.70158f;
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	if ((t /= d / 2) < 1) return c / 2 * (t * t * (((s *= (1.525f)) + 1) * t - s)) + b; // TODO: ehrich: operation with s is undefined
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	float postFix = t -= 2;
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	return c / 2 * ((postFix)*t * (((s *= (1.525f)) + 1) * t + s) + 2) + b; // TODO: ehrich: operation with s is undefined
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}
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static real_t out_in(real_t t, real_t b, real_t c, real_t d) {
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	return (t < d / 2) ? out(t * 2, b, c / 2, d) : in((t * 2) - d, b + c / 2, c / 2, d);
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}
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}; // namespace back
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Tween::interpolater Tween::interpolaters[Tween::TRANS_COUNT][Tween::EASE_COUNT] = {
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	{ &linear::in, &linear::out, &linear::in_out, &linear::out_in },
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	{ &sine::in, &sine::out, &sine::in_out, &sine::out_in },
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	{ &quint::in, &quint::out, &quint::in_out, &quint::out_in },
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	{ &quart::in, &quart::out, &quart::in_out, &quart::out_in },
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	{ &quad::in, &quad::out, &quad::in_out, &quad::out_in },
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	{ &expo::in, &expo::out, &expo::in_out, &expo::out_in },
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	{ &elastic::in, &elastic::out, &elastic::in_out, &elastic::out_in },
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	{ &cubic::in, &cubic::out, &cubic::in_out, &cubic::out_in },
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	{ &circ::in, &circ::out, &circ::in_out, &circ::out_in },
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	{ &bounce::in, &bounce::out, &bounce::in_out, &bounce::out_in },
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	{ &back::in, &back::out, &back::in_out, &back::out_in },
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};
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real_t Tween::_run_equation(TransitionType p_trans_type, EaseType p_ease_type, real_t t, real_t b, real_t c, real_t d) {
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	interpolater cb = interpolaters[p_trans_type][p_ease_type];
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	ERR_FAIL_COND_V(cb == NULL, b);
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	return cb(t, b, c, d);
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}
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