codepens/dragon/dist/script.js

80 lines
2.0 KiB
JavaScript

"use strict";
// Ported from flash
// credits https://www.deviantart.com/gifhaas/art/Dragon-8681899 dragon by GifHaas on DeviantArt
const screen = document.getElementById("screen");
const xmlns = "http://www.w3.org/2000/svg";
const xlinkns = "http://www.w3.org/1999/xlink";
window.addEventListener(
"pointermove",
(e) => {
pointer.x = e.clientX;
pointer.y = e.clientY;
rad = 0;
},
false
);
const resize = () => {
width = window.innerWidth;
height = window.innerHeight;
};
let width, height;
window.addEventListener("resize", () => resize(), false);
resize();
const prepend = (use, i) => {
const elem = document.createElementNS(xmlns, "use");
elems[i].use = elem;
elem.setAttributeNS(xlinkns, "xlink:href", "#" + use);
screen.prepend(elem);
};
const N = 40;
const elems = [];
for (let i = 0; i < N; i++) elems[i] = { use: null, x: width / 2, y: 0 };
const pointer = { x: width / 2, y: height / 2 };
const radm = Math.min(pointer.x, pointer.y) - 20;
let frm = Math.random();
let rad = 0;
for (let i = 1; i < N; i++) {
if (i === 1) prepend("Cabeza", i);
else if (i === 8 || i === 14) prepend("Aletas", i);
else prepend("Espina", i);
}
const run = () => {
requestAnimationFrame(run);
let e = elems[0];
const ax = Math.cos(3 * frm) * rad * width / height;
const ay = Math.sin(4 * frm) * rad * height / width;
e.x += (ax + pointer.x - e.x) / 10;
e.y += (ay + pointer.y - e.y) / 10;
for (let i = 1; i < N; i++) {
let e = elems[i];
let ep = elems[i - 1];
const a = Math.atan2(e.y - ep.y, e.x - ep.x);
e.x += (ep.x - e.x + (Math.cos(a) * (100 - i)) / 5) / 4;
e.y += (ep.y - e.y + (Math.sin(a) * (100 - i)) / 5) / 4;
const s = (162 + 4 * (1 - i)) / 50;
e.use.setAttributeNS(
null,
"transform",
`translate(${(ep.x + e.x) / 2},${(ep.y + e.y) / 2}) rotate(${
(180 / Math.PI) * a
}) translate(${0},${0}) scale(${s},${s})`
);
}
if (rad < radm) rad++;
frm += 0.003;
if (rad > 60) {
pointer.x += (width / 2 - pointer.x) * 0.05;
pointer.y += (height / 2 - pointer.y) * 0.05;
}
};
run();