pocketpy/src/modules/easing.cpp

#include "pocketpy/modules/easing.hpp"
#include "pocketpy/interpreter/bindings.hpp"

#include <cmath>

namespace pkpy {
// https://easings.net/

const double kPi = 3.1415926545;

static double easeLinear(double x) { return x; }

static double easeInSine(double x) { return 1.0 - std::cos(x * kPi / 2); }

static double easeOutSine(double x) { return std::sin(x * kPi / 2); }

static double easeInOutSine(double x) { return -(std::cos(kPi * x) - 1) / 2; }

static double easeInQuad(double x) { return x * x; }

static double easeOutQuad(double x) { return 1 - std::pow(1 - x, 2); }

static double easeInOutQuad(double x) {
    if(x < 0.5) {
        return 2 * x * x;
    } else {
        return 1 - std::pow(-2 * x + 2, 2) / 2;
    }
}

static double easeInCubic(double x) { return x * x * x; }

static double easeOutCubic(double x) { return 1 - std::pow(1 - x, 3); }

static double easeInOutCubic(double x) {
    if(x < 0.5) {
        return 4 * x * x * x;
    } else {
        return 1 - std::pow(-2 * x + 2, 3) / 2;
    }
}

static double easeInQuart(double x) { return std::pow(x, 4); }

static double easeOutQuart(double x) { return 1 - std::pow(1 - x, 4); }

static double easeInOutQuart(double x) {
    if(x < 0.5) {
        return 8 * std::pow(x, 4);
    } else {
        return 1 - std::pow(-2 * x + 2, 4) / 2;
    }
}

static double easeInQuint(double x) { return std::pow(x, 5); }

static double easeOutQuint(double x) { return 1 - std::pow(1 - x, 5); }

static double easeInOutQuint(double x) {
    if(x < 0.5) {
        return 16 * std::pow(x, 5);
    } else {
        return 1 - std::pow(-2 * x + 2, 5) / 2;
    }
}

static double easeInExpo(double x) { return x == 0 ? 0 : std::pow(2, 10 * x - 10); }

static double easeOutExpo(double x) { return x == 1 ? 1 : 1 - std::pow(2, -10 * x); }

static double easeInOutExpo(double x) {
    if(x == 0) {
        return 0;
    } else if(x == 1) {
        return 1;
    } else if(x < 0.5) {
        return std::pow(2, 20 * x - 10) / 2;
    } else {
        return (2 - std::pow(2, -20 * x + 10)) / 2;
    }
}

static double easeInCirc(double x) { return 1 - std::sqrt(1 - std::pow(x, 2)); }

static double easeOutCirc(double x) { return std::sqrt(1 - std::pow(x - 1, 2)); }

static double easeInOutCirc(double x) {
    if(x < 0.5) {
        return (1 - std::sqrt(1 - std::pow(2 * x, 2))) / 2;
    } else {
        return (std::sqrt(1 - std::pow(-2 * x + 2, 2)) + 1) / 2;
    }
}

static double easeInBack(double x) {
    const double c1 = 1.70158;
    const double c3 = c1 + 1;
    return c3 * x * x * x - c1 * x * x;
}

static double easeOutBack(double x) {
    const double c1 = 1.70158;
    const double c3 = c1 + 1;
    return 1 + c3 * std::pow(x - 1, 3) + c1 * std::pow(x - 1, 2);
}

static double easeInOutBack(double x) {
    const double c1 = 1.70158;
    const double c2 = c1 * 1.525;
    if(x < 0.5) {
        return (std::pow(2 * x, 2) * ((c2 + 1) * 2 * x - c2)) / 2;
    } else {
        return (std::pow(2 * x - 2, 2) * ((c2 + 1) * (x * 2 - 2) + c2) + 2) / 2;
    }
}

static double easeInElastic(double x) {
    const double c4 = (2 * kPi) / 3;
    if(x == 0) {
        return 0;
    } else if(x == 1) {
        return 1;
    } else {
        return -std::pow(2, 10 * x - 10) * std::sin((x * 10 - 10.75) * c4);
    }
}

static double easeOutElastic(double x) {
    const double c4 = (2 * kPi) / 3;
    if(x == 0) {
        return 0;
    } else if(x == 1) {
        return 1;
    } else {
        return std::pow(2, -10 * x) * std::sin((x * 10 - 0.75) * c4) + 1;
    }
}

static double easeInOutElastic(double x) {
    const double c5 = (2 * kPi) / 4.5;
    if(x == 0) {
        return 0;
    } else if(x == 1) {
        return 1;
    } else if(x < 0.5) {
        return -(std::pow(2, 20 * x - 10) * std::sin((20 * x - 11.125) * c5)) / 2;
    } else {
        return (std::pow(2, -20 * x + 10) * std::sin((20 * x - 11.125) * c5)) / 2 + 1;
    }
}

static double easeOutBounce(double x) {
    const double n1 = 7.5625;
    const double d1 = 2.75;
    if(x < 1 / d1) {
        return n1 * x * x;
    } else if(x < 2 / d1) {
        x -= 1.5 / d1;
        return n1 * x * x + 0.75;
    } else if(x < 2.5 / d1) {
        x -= 2.25 / d1;
        return n1 * x * x + 0.9375;
    } else {
        x -= 2.625 / d1;
        return n1 * x * x + 0.984375;
    }
}

static double easeInBounce(double x) { return 1 - easeOutBounce(1 - x); }

static double easeInOutBounce(double x) {
    return x < 0.5 ? (1 - easeOutBounce(1 - 2 * x)) / 2 : (1 + easeOutBounce(2 * x - 1)) / 2;
}

void add_module_easing(VM* vm) {
    PyObject* mod = vm->new_module("easing");

#define EASE(name)                                                                                                     \
    vm->bind_func(mod, #name, 1, [](VM* vm, ArgsView args) {                                                           \
        f64 t = CAST(f64, args[0]);                                                                                    \
        return VAR(ease##name(t));                                                                                     \
    });

    EASE(Linear)
    EASE(InSine)
    EASE(OutSine)
    EASE(InOutSine)
    EASE(InQuad)
    EASE(OutQuad)
    EASE(InOutQuad)
    EASE(InCubic)
    EASE(OutCubic)
    EASE(InOutCubic)
    EASE(InQuart)
    EASE(OutQuart)
    EASE(InOutQuart)
    EASE(InQuint)
    EASE(OutQuint)
    EASE(InOutQuint)
    EASE(InExpo)
    EASE(OutExpo)
    EASE(InOutExpo)
    EASE(InCirc)
    EASE(OutCirc)
    EASE(InOutCirc)
    EASE(InBack)
    EASE(OutBack)
    EASE(InOutBack)
    EASE(InElastic)
    EASE(OutElastic)
    EASE(InOutElastic)
    EASE(InBounce)
    EASE(OutBounce)
    EASE(InOutBounce)

#undef EASE
}
}  // namespace pkpy