ロード画面のあれ

Main.cpp

# include <Siv3D.hpp>

void DrawLoading(
    const Vec2& pos,
    double radius,
    int num,
    double speed,
    std::function<void(const Vec2& pos, double radius, double radian)> func)
{
    const double dNum = static_cast<double>(num);

    const double dif = TwoPi / dNum;

    for (int i = 0; i < num; ++i)
    {
        const double radian = i * dif;

        const Vec2 tPos = pos + Circular(radius, radian);

        const double phase = System::FrameCount() * (-speed) + radian / 2.0;

        const double tRadius = atan(Tan(phase)) / Pi + 1.0 / 2.0;

        func(tPos, tRadius, radian);
    }
}

void Main()
{
    const Font font(30);

    std::array<std::function<void(const Vec2& pos, double radius, double radian)>, 3> funcs = {
            [](const Vec2& pos, double radius, double radian)
        {
            Circle(pos, radius * 10.0).draw(); 
        },
            [](const Vec2& pos, double radius, double radian)
        {
            RectF(radius*10.0, radius*10.0).setCenter(pos).rotate(radian).draw();
        },
            [](const Vec2& pos, double radius, double radian)
        {
            RectF(10.0, 20.0).setCenter(pos).rotate(radian).draw(ColorF(1.0, radius));
        }
    };

    int i = 0;

    while (System::Update())
    {
        font.draw(L"画面クリックで種類を変える");

        if (Mouse::LeftClicked())
        {
            if (!(++i < funcs.size()))
            {
                i = 0;
            }
        }

        DrawLoading(Mouse::Pos(), 50.0, 10, 0.05, funcs.at(i));
    }
}