dust/js/animation3.js

// Single particle movement.
// Goal: per-frame decisions
// 20 x 20 grid

// The trickiest portion of this iteration was animating the curved paths.  Calculating arc length (for scalar speed) along an elliptical
// geometry is quite difficult, so the current solution uses circular paths, which change radius and sometimes rotation after a random
// number of frames have emitted.  A smoothstep cubic curve was considered, but maintaining consistent entry and exit angles will affect
// performance for large particle counts.

import Rx, { Observable } from 'rxjs';
import AnimationBase from './animation0';
import DOM from './dom';
import Store from './store';

const speed = 6;
const grid = {};
const t45 = Math.PI / 4;
const t90 = Math.PI / 2;
const t270 = 3 * Math.PI / 2;
const t360 = Math.PI * 2;

const movementCircle = document.createElement('div');
movementCircle.className = 'anim3-movement-circle';

const visionGrid = document.createElement('div');
visionGrid.className = 'anim3-vision-grid';

const particle = document.createElement('div');
particle.className = 'anim3-particle';

const visionGridPoints = calculateVisionGridPoints();

function move(store) {
    let {
        clockwise,
        interval,
        circleX,
        circleY,
        radius,
        theta
    } = store.get();


    if (interval <= 0) {
        const particleX = circleX + radius * Math.cos(theta);
        const particleY = circleY - radius * Math.sin(theta);

        interval = Math.round(Math.random() * 10) + 50;
        radius = Math.round(Math.random() * 200) + 50;

        // IF SEEING A WALL: tight 180
        // if ( < visionRadius
        // if (Math.random() < 0.3) {
        //     console.warn("turn!")
        //     state.radius = 20;
        //     state.interval = Math.PI * 20 / speed;
        // }

        if (Math.random() < 0.5) {
            clockwise = !clockwise;
            theta = (theta > Math.PI ? theta - Math.PI : theta + Math.PI);
            radius *= -1;
        }

        circleX = particleX - radius * Math.cos(theta);
        circleY = particleY + radius * Math.sin(theta);
    }

    // interval -= 1;

    // TODO store delta
    const delta = speed / radius;
    theta += (clockwise ? -delta : +delta);
    theta %= t360;

    store.set({
        clockwise,
        interval,
        circleX,
        circleY,
        radius,
        theta
    });

    // detectWall(store);
}

function detectWall(store) {
    // const { circleX, circleY, radius, theta } = store.get();
    // const len = visionGridPoints.length;
    //
    // for (let i = 0; i < len; i++) {
    //     const { x, y } = visionGridPoints[i];
    //     if (grid[x] && grid[x][y] && grid[x][y].type === 'wall') {
    //         console.warn("Wall detected", x, y);
    //         return true;
    //     }
    // }
    //
    // return false;
}

function transformMovementCircle(store) {
    // TODO UPDATE ONLY IF THETA CHANGED - MUST HAVE PREVSTATE
    const { circleX, circleY, radius, theta } = store.get();

    movementCircle.style.left = `${circleX - radius}px`;
    movementCircle.style.top = `${circleY - radius}px`;
    movementCircle.style.height = `${2 * radius}px`;
    movementCircle.style.width = `${2 * radius}px`;
    movementCircle.style.borderRadius = `${radius}px`;
}

function transformParticle(store) {
    const { clockwise, circleX, circleY, radius, theta } = store.get();
    const rad = clockwise ? Math.PI - theta : t360 - theta;

    particle.style.left = `${circleX + radius * Math.cos(theta)}px`;
    particle.style.top = `${circleY - radius * Math.sin(theta)}px`;
    particle.style.transform = `rotate(${rad}rad)`;
}

function transformVisionGrid(store) {
    const { clockwise, circleX, circleY, radius, theta } = store.get();
    const particleX = circleX + radius * Math.cos(theta);
    const particleY = circleY - radius * Math.sin(theta);

    const r0 = Math.min(theta, theta - Math.PI);
    const r1 = Math.max(theta, theta + Math.PI);

    visionGridPoints.forEach(({ x, y, alpha, div }) => {
        if (alpha >= 0 && alpha <= r0) {
            div.style.display = (clockwise ? 'none' : 'block');
        } else if (alpha >= theta && alpha <= r1) {
            div.style.display = (clockwise ? 'none' : 'block');
        } else {
            div.style.display = (clockwise ? 'block' : 'none');
        }

        div.style.left = `${x + particleX}px`;
        div.style.top = `${-y + particleY}px`;
    });
}

function calculateVisionGridPoints() {
    const visionRadius = 50;
    const gridSize = 5;

    const squareGrid = [];
    for (let x = -visionRadius; x <= visionRadius; x += gridSize) {
        for (let y = -visionRadius; y <= visionRadius; y += gridSize) {
            let alpha = Math.atan(y / x);

            if (x === 0 && y === 0) {
                alpha = 0;
            } else if (x === 0 && y < 0) {
                alpha = t270;
            } else if (y === 0 && x < 0) {
                alpha = Math.PI;
            } else if (x === 0 && y > 0) {
                alpha = t90;
            } else if (x < 0 && y < 0) {
                alpha = alpha + Math.PI;
            } else if (x <= 0) {
                alpha = Math.PI + alpha;
            } else if (y < 0) {
                alpha = 2 * Math.PI + alpha;
            }

            squareGrid.push({ x, y, alpha });
        }
    }

    const visionRadiusSquared = Math.pow(visionRadius, 2);

    return squareGrid.reduce((acc, point) => {
        if ((Math.pow(point.x, 2) + Math.pow(point.y, 2)) > visionRadiusSquared) {
            return acc;
        }

        const div = document.createElement('div');
        div.className = 'anim3-dot';

        acc.push(Object.assign(point, { div }));
        return acc;
    }, []);
}

function reset() {
    while (DOM.container.childNodes.length) {
        DOM.container.removeChild(DOM.container.firstChild);
    }

    const store = new Store({
        clockwise: true,
        interval: 10,
        circleX: 300,
        circleY: 300,
        radius: 150,
        theta: 0
    });

    move(store);

    transformParticle(store);
    transformMovementCircle(store);
    transformVisionGrid(store);

    DOM.container.appendChild(particle);
    DOM.container.appendChild(movementCircle);

    visionGridPoints.forEach(point => {
        DOM.container.appendChild(point.div);
    });

    return store;
};

function init() {
    const store = reset();

    for (let x = 0; x <= 600; x += 5) {
        grid[x] = {};
        for (let y = 0; y <= 600; y += 5) {
            grid[x][y] = { type: null };

            if (x === 0 || y === 0 || x === 600 || y === 600) {
                grid[x][y] = { type: 'wall' };
            }
        }
    }

    const stop$ = Rx.Observable.fromEvent(DOM.container, 'stop');
    const fps$ = Rx.Observable.interval(1000 / 32)
        .map(_ => store)
        .take(300)
        // .take(0)
        // .takeUntil(stop$); console.error("CLICK TO STOP");

    const click$ = Rx.Observable.fromEvent(DOM.container, 'click');
    click$.subscribe(() => {
        DOM.container.dispatchEvent(new CustomEvent('stop'));
    });

    fps$.subscribe(move);
    fps$.subscribe(transformParticle);
    fps$.subscribe(transformMovementCircle);
    fps$.subscribe(transformVisionGrid);
};

const Animation3 = Object.assign({}, AnimationBase, { init, reset });

export default Animation3;