Force-Field/index.html at main · Mearleo/Force-Field · GitHub

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<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Particle Field</title>
</head>
<body>
    <canvas></canvas>
    <div>
        <button onclick="toggle_trace()">toggle trace (t)</button>
        <button onclick="clear_canvas()">clear (c)</button>
        <button onclick="download()">save (s)</button>
    </div>
    <style>
        body {
            overflow: hidden;
            margin: 0;
            padding: 0;
        }

        canvas {
            position: absolute;
            width: 100vw;
            height: 100vh;
        }

        canvas, body, html, * {
            touch-action: none;
            -webkit-user-select: none; /* Safari */
            -ms-user-select: none; /* IE 10 and IE 11 */
            user-select: none; /* Standard syntax */
        }

        div {
            position: absolute;
            top: 10px;
            left: 10px;
        }
    </style>
    <script>
        console.clear();
        const canvas = document.querySelector("canvas");
        const ctx = canvas.getContext("2d");
        canvas.width = window.innerWidth;
        canvas.height = window.innerHeight;
        ctx.textAlign = "right";
        ctx.textBaseline = 'top';

        const observer = new ResizeObserver(resizeTheCanvasToDisplaySize)
        observer.observe(canvas);

        function resizeTheCanvasToDisplaySize(entries) {
            const entry = entries[0];
            let width;
            let height;
            if (entry.devicePixelContentBoxSize) {
                width = entry.devicePixelContentBoxSize[0].inlineSize;
                height = entry.devicePixelContentBoxSize[0].blockSize;
            } else if (entry.contentBoxSize) {
                // fallback for Safari that will not always be correct
                width = Math.round(entry.contentBoxSize[0].inlineSize * devicePixelRatio);
                height = Math.round(entry.contentBoxSize[0].blockSize * devicePixelRatio);
            }
            canvas.width = width;
            canvas.height = height;
            ctx.fillStyle = "#AFA";
            shorter_side = Math.min(canvas.width, canvas.height);
            view_ratio = shorter_side/(CANVAS_VIEW*2);
            shorter_offset = Math.min(canvas.offsetWidth, canvas.offsetHeight);
            view_ratio_offset = shorter_offset * CANVAS_VIEW * 2;
            if (trace) {
                ctx.globalAlpha = .01;
            } else {
                ctx.globalAlpha = 1;
            }
        }

        let x_pos = [];
        let y_pos = [];
        let x_vel = [];
        let y_vel = [];

        let mouse_x = 0;
        let mouse_y = 0;
        let mouse_down = false;

        canvas.addEventListener("contextmenu", e => {
            e.preventDefault();
        });

        canvas.addEventListener("mousemove", e => {
            mouse_x = (e.pageX - canvas.offsetWidth/2) / shorter_offset * CANVAS_VIEW * 2;
            mouse_y = -(e.pageY - canvas.offsetHeight/2) / shorter_offset * CANVAS_VIEW * 2;
        });

        canvas.addEventListener("touchmove", e => {
            mouse_x = (e.touches[0].clientX - canvas.offsetWidth/2) / shorter_offset * CANVAS_VIEW * 2;
            mouse_y = -(e.touches[0].clientY - canvas.offsetHeight/2) / shorter_offset * CANVAS_VIEW * 2;
        });

        canvas.addEventListener("mousedown", e => {
            mouse_x = (e.pageX - canvas.offsetWidth/2) / shorter_offset * CANVAS_VIEW * 2;
            mouse_y = -(e.pageY - canvas.offsetHeight/2) / shorter_offset * CANVAS_VIEW * 2;
            mouse_down = true;
        });
        canvas.addEventListener("mouseup", e => {
            mouse_down = false;
            e.preventDefault();
        });
        canvas.addEventListener("touchstart", e => {
            mouse_x = (e.touches[0].clientX - canvas.offsetWidth/2) / shorter_offset * CANVAS_VIEW * 2;
            mouse_y = -(e.touches[0].clientY - canvas.offsetHeight/2) / shorter_offset * CANVAS_VIEW * 2;
            mouse_down = true;
        });

        canvas.addEventListener("touchend", e => {
            mouse_down = false;
            e.preventDefault();
        });

        const size = 100;
        const create_scale = 1/size;
        for (let y = 0; y < size; y++) {
            for (let x = 0; x < size; x++) {
                    x_pos.push((x - size/2) * create_scale);
                    y_pos.push((y - size/2) * create_scale);
                    x_vel.push(0);
                    y_vel.push(0);
            }
        }

        const CANVAS_VIEW = 10;
        let shorter_side = Math.min(canvas.width, canvas.height);
        let view_ratio = shorter_side/(CANVAS_VIEW*2);
        let shorter_offset = Math.min(canvas.offsetWidth, canvas.offsetHeight);
        function draw_point(x, y) {
            ctx.fillRect(x*view_ratio + canvas.width/2, -y*view_ratio + canvas.height/2, 1, 1);
        }


        const delta_time = 0.021;
        let last_time = new Date().getTime();
        let delta_value = 0;


        let trace = false;
        var download = function() {
            var link = document.createElement('a');
            link.download = 'particle_image.png';
            link.href = canvas.toDataURL();
            link.click();
        }
        var clear_canvas = function() {
            ctx.clearRect(0, 0, canvas.width, canvas.height);
            ctx.save();
            ctx.fillStyle = "#222";
            ctx.globalAlpha = 1;
            ctx.fillRect(0, 0, canvas.width, canvas.height);
            ctx.restore();
        }
        var toggle_trace = function() {
                if (trace) {
                    trace = false;
                    ctx.globalAlpha = 1;
                } else {
                    clear_canvas();
                    trace = true;
                    ctx.globalAlpha = .01;
                }
        }
        window.addEventListener("keydown", e => {
            if (e.key == "s") download();
            if (e.key == "c") clear_canvas();
            if (e.key == "t") toggle_trace();
        });


        const RESITANCE = 0.995;
        (function loop() {
            window.requestAnimationFrame(loop);
            if(!trace) clear_canvas();
            delta_value += ((new Date().getTime() - last_time) - delta_value) * 0.08;
            if(!trace) ctx.fillText(Math.floor(delta_value), canvas.width, 0);
            last_time = new Date().getTime();

            for (let i = 0; i < x_pos.length; i++) {
                x_pos[i] += x_vel[i] * delta_time;
                y_pos[i] += y_vel[i] * delta_time;


                if(mouse_down) {
                    let delta_x = mouse_x - x_pos[i];
                    let delta_y = mouse_y - y_pos[i];
                    const mouse_distance = Math.hypot(delta_x, delta_y);
                    //const linear_attraction = 500 / (mouse_distance**2 + 0);
                    const linear_attraction = 500 / (mouse_distance + 10);
                    const attraction_over_dist = linear_attraction / mouse_distance;
                    delta_x *= attraction_over_dist;
                    delta_y *= attraction_over_dist;
                    x_vel[i] = (x_vel[i] + delta_x * delta_time) * RESITANCE;
                    y_vel[i] = (y_vel[i] + delta_y * delta_time) * RESITANCE;
                }

                draw_point(x_pos[i], y_pos[i]);
            }

        })();
    </script>
</body>
</html>