Vehicles implement by OpenSiv3D from The Nature of Code.

openSiv3D_vehicle

#include "stdafx.h"
inline void _limit(Vec2& v, double a)
{
	double b = v.lengthSq();
	if (b > a*a) {
		v /= sqrt((float)b);
	}
	v *= a;
}
inline double heading(Vec2 v)
{
	return atan2(v.y, v.x);
}
inline double _Radians(double d)
{
	// 180d = PI
	// 360 = 2*PI
	return 2 * M_PI / 360 * d;
}

struct Target {
	Target()
		:
		position(Vec2(Random(0, Window::Width()), Random(0, Window::Height()))),
		velocity(Vec2(Random(-2,2), Random(-2,2))),
		acceleration(Vec2::Zero())
	{
	}
	Target(double x, double y)
		: position(Vec2(x, y)),
		velocity(Vec2(Random(-2, 2), Random(-2, 2))),
		acceleration(Vec2::Zero())
	{
	}
	void update()
	{
		velocity += acceleration;
		position += velocity;
		acceleration *= 0.0;
		if (position.x < 0) {
			position.x = Window::Width();
		}
		else if (position.x > Window::Width()) {
			position.x = 0;
		}
		if (position.y < 0) {
			position.y = Window::Height();
		}
		else if (position.y > Window::Height()) {
			position.y = 0;
		}
	}
	void display()
	{
		Circle(position, r).draw(Color(170, 170, 170)).drawFrame(1, Palette::Black);
	}
	void run()
	{
		update();
		display();
	}
	Vec2 position;
	Vec2 velocity;
	Vec2 acceleration;
	double r = 10;
};

struct Vehicle {
	Vehicle()
		:
		position(Vec2(Random(0, Window::Width()), Random(0, Window::Height()))),
		velocity(Vec2::Zero()),
		acceleration({ Random(-3,3),Random(-3,3) }),
		mass(mass),
		maxspeed(7.0),
		maxforce(0.09)
	{
	}
	Vehicle(double x, double y, double mass = 1)
		:
		position({ x, y }),
		velocity(Vec2::Zero()),
		acceleration({Random(-1,1),Random(-1,1)}),
		mass(mass),
		maxspeed(1.0),
		maxforce(0.005)
	{
	}
	Vec2 position;
	Vec2 velocity;
	Vec2 acceleration;
	double maxspeed;
	double maxforce;
	double mass;
	// F=AM, A=F/M
	void applyForce(const Vec2& force)
	{
		auto v = force.xy();
		acceleration += v;
	}
	void seek(Target target)
	{
		// 望む速度
		Vec2 desired = target.position - position;
		desired.normalize();
		desired *= maxspeed;
		// 操舵力=望む速度-現在の速度		
		Vec2 steer = desired - velocity;
		// steer.limit
		_limit(steer, maxforce);
		
		applyForce(steer);
	}
	void update()
	{
		velocity += acceleration;
		position += velocity;
		acceleration *= 0;

		if (position.x < 0) {
			position.x = Window::Width();
		}
		else if (position.x > Window::Width()) {
			position.x = 0;
		}
		if (position.y < 0) {
			position.y = Window::Height();
		}
		else if (position.y > Window::Height()) {
			position.y = 0;
		}
	}
	void display()
	{
		auto theta = heading(velocity) + M_PI/2;
		Triangle(position, 10).rotated(theta).draw().drawFrame(1.0, Palette::Black);
	}
	void run(Target target) {
		seek(target);
		update();
		display();
	}
};

void Main()
{
	Window::Resize(640, 480);
	Graphics::SetBackground(Color(240, 240, 240, 50));

	const Font font(30);
	Target target(100, 100);
	std::vector<Vehicle> vs(50);

	while (System::Update())
	{
		font(L"💖OpenSiv3D!🐣").drawAt(Vec2(150, 20), Palette::Black);

		for (auto& v : vs) {
			v.run(target);
		}
		target.run();

		//font(Cursor::Pos()).draw(20, 400);
		//Circle(Cursor::Pos(), 60).draw(ColorF(1, 0, 0, 0.5));
		/*
		Line(Vec2(0, 200), Vec2(400, 200)).draw(Palette::Black);
		Line(Vec2(200, 0), Vec2(200, 400)).draw(Palette::Black);
		Triangle(200, 200, 20)
			//.setCentroid(Vec2(200, 200))
			.rotated(_Radians(45))
			.draw(Palette::Black);// .drawFrame(1.0, Palette::Black);
		Line(Vec2(200, 200), Vec2(400, 0)).draw(Palette::Blue);
		*/
	}
}