stars.js

function colorTemperatureToRGB(kelvin) {
    var temp = kelvin / 100;
    var red, green, blue;
    if (temp <= 66) {
        red = 255;
        green = temp;
        green = 99.4708025861 * Math.log(green) - 161.1195681661;
        if (temp <= 19) {
            blue = 0;
        } else {
            blue = temp - 10;
            blue = 138.5177312231 * Math.log(blue) - 305.0447927307;
        }
    } else {
        red = temp - 60;
        red = 329.698727446 * Math.pow(red, -0.1332047592);
        green = temp - 60;
        green = 288.1221695283 * Math.pow(green, -0.0755148492);
        blue = 255;
    }
    return [clamp(red, 0, 255), clamp(green, 0, 255), clamp(blue, 0, 255)];
}

function clamp(x, min, max) {
    if (x < min) {
        return min;
    } else if (x > max) {
        return max;
    }
    return x;
}

const types = [
    {
        type: "O",
        temperature: 40000,
        mass: 50 * MASS_SUN,
        radius: 10 * RADIUS_SUN,
        prob: 0.00001,
    },
    {
        type: "B",
        temperature: 20000,
        mass: 10 * MASS_SUN,
        radius: 5 * RADIUS_SUN,
        prob: 0.1,
    },
    {
        type: "A",
        temperature: 8500,
        mass: 2 * MASS_SUN,
        radius: 1.7 * RADIUS_SUN,
        prob: 0.7,
    },
    {
        type: "F",
        temperature: 6500,
        mass: 1.5 * MASS_SUN,
        radius: 1.3 * RADIUS_SUN,
        prob: 2,
    },
    {
        type: "G",
        temperature: 5700,
        mass: MASS_SUN,
        radius: RADIUS_SUN,
        prob: 3.5,
    },
    {
        type: "K",
        temperature: 4500,
        mass: 0.7 * MASS_SUN,
        radius: 0.8 * RADIUS_SUN,
        prob: 8,
    },
    {
        type: "M",
        temperature: 3200,
        mass: 0.2 * MASS_SUN,
        radius: 0.3 * RADIUS_SUN,
        prob: 80,
    },
];

const types_name = types.map((a) => a.type);

const total_prob = types.reduce((a, b) => a + b.prob, 0);

function generateStar(type) {
    let star = types.find((star) => star.type === type);
    star.color = color(...colorTemperatureToRGB(star.temperature));
    return star;
}

function sampleStar() {
    const pick = random(0, total_prob);
    let acc = 0;
    for (let i = 0; i < types.length; i++) {
        acc += types[i].prob;
        if (acc > pick) {
            return types[i].type;
        }
    }
}