我是编程新手,拿到了一份学校作业,需要用 p5.js 创建地球绕太阳的模拟。我们有一个简化的计算引力的方法,但我想使用实际的公式 (Fg = GMm/r^2)。在我的代码中,一个像素等于10^9米或一百万千米。如果我使用太阳和地球的实际质量以及它们之间的实际距离,我必须将地球绕太阳的速度设置为每秒1个像素或1000000千米/秒,这大约是实际轨道速度的30000倍。我的代码:
x = 550;
y = 400;
vy = -1;
vx = 0;
dt = 1;
sunSize = 80;
planetSize = 10;
// 1 pixel equals 1 million km
canvasSize = 800;
starAmount = 600;
function setup() {
frameRate(60);
noStroke()
solarXY = 0.5 * canvasSize;
xSun = solarXY;
ySun = solarXY;
createCanvas(canvasSize, canvasSize);
M = 1.989 * pow(10, 30);
m = 5.972 * pow(10, 24);
background(0);
for (i = 0; i < starAmount; i++) {
starX = Math.random() * canvasSize;
starY = Math.random() * canvasSize;
starSize = Math.random() * 3 + 1
ellipse(starX, starY, starSize, starSize);
}
fill(255, 192, 0);
ellipse(xSun, ySun, sunSize, sunSize);
}
function draw() {
r = sqrt(sq(xSun - x) + sq(ySun - y)) * pow(10, 9);
Fg = 6.67 * pow(10, -11) * m * M / sq(r);
if (x >= xSun) {
angle = atan((ySun - y) / (x - xSun));
} else {
angle = PI + atan((ySun - y) / (x - xSun));
}
xOld = x;
yOld = y;
Fgx = cos(angle) * Fg
Fgy = sin(angle) * Fg
ay = Fgy / m;
ax = -Fgx / m;
vy += ay * dt;
vx += ax * dt;
y += vy * dt;
x += vx * dt;
fill(30);
ellipse(xOld, yOld, planetSize, planetSize);
fill(0, 0, 192);
ellipse(x, y, planetSize, planetSize);
}
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