楕円軌道

https://scrapbox.io/files/64d7317596732a001cb26328.png

code:楕円軌道.cpp

# include <Siv3D.hpp>

Vec2 elliptical(const Ellipse& ellipse, double theta) {

Vec2 pos = OffsetCircular({ 0,0 }, ellipse.a, theta);

pos.y *= ellipse.b / ellipse.a;

pos += ellipse.center;

return pos;

}

void Main()

{

Texture texture{ U"example/siv3d-kun.png" };

const Ellipse ellipse{ Scene::Center(),200,50 };

constexpr int32 N = 12;

constexpr double time = 3;

while (System::Update())

{

for (auto i : step(N)) {

double t = Periodic::Sawtooth0_1(time, Scene::Time() + i * time / N);

double theta = t * 360_deg + 90_deg;

if (0.5 <= t) {

elliptical(ellipse, theta).asCircle(10).draw(HSV{ 360 * i / (double)N });

}

}

texture.drawAt(Scene::Center());

for (auto i : step(N)) {

double t = Periodic::Sawtooth0_1(time, Scene::Time() + i * time / N);

double theta = t * 360_deg + 90_deg;

if (t < 0.5) {

elliptical(ellipse, theta).asCircle(10).draw(HSV{ 360 * i / (double)N });

}

}

}

}