利用HTML5实现Canvas彩色浮动粒子特效



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特效描述:利用HTML5实现 Canvas 彩色浮动 粒子特效,利用HTML5实现Canvas彩色浮动粒子特效

代码结构

1. HTML代码

<p>点击圆点驱散变小。</p>
<script>
// start particle simulation
simulate(
    '2d', {
        init: function() {
            this.spray(150, function() {
                return [
                    null,
                    null,
                    Vector.create(
                        this.width * Math.random(),
                        this.height * Math.random()
                    ),
                    Vector.random(1),
                    .75 + (Math.random() * .5),
                    100 * Math.random(), [
                        this.behavior.cohesion(),
                        this.behavior.alignment(),
                        this.behavior.separation(),
                        this.behavior.limit(1 + Math.random()),
                        this.behavior.wrap(5),
                        this.behavior.move()
                    ]
                ]
            })
        },
        tick: function() {
        },
        beforePaint: function() {
            this.clear();
        },
        paint: function(particle) {
            var p = particle.position;
            var v = particle.velocity;
            var s = particle.stimulated || 0;
            var l = particle.life;
            this.paint.circle(p.x, p.y, v.magnitudeSquared, 'hsla(' + v.angle + ',100%,50%,1)');
        },
        afterPaint: function() {
            // nothing
        },
        action: function(x, y) {
            // disperse if near
            this.particles.forEach(function(p) {
                if (Vector.distanceSquared(p.position, {
                        x: x,
                        y: y
                    }) < 4000) {
                    p.velocity.randomize(100);
                    p.position.x += p.velocity.x;
                    p.position.y += p.velocity.y;
                }
            });
        }
    }
);
setTimeout(() => {
    document.querySelector('p').style.opacity = 0;
}, 3000);
// "simulate" particle simulation logic
/**
 * Constants
 */
PI_2 = Math.PI / 2;
PI_180 = Math.PI / 180;
/**
 * Random
 */
var Random = {
    between: function(min, max) {
        return min + (Math.random() * (max - min));
    }
}
/**
 * 2D Vector Class
 */
function Vector(x, y) {
    this._x = x || 0;
    this._y = y || 0;
}
Vector.create = function(x, y) {
    return new Vector(x, y);
};
Vector.add = function(a, b) {
    return new Vector(a.x + b.x, a.y + b.y);
};
Vector.subtract = function(a, b) {
    return new Vector(a.x - b.x, a.y - b.y);
};
Vector.random = function(range) {
    var v = new Vector();
    v.randomize(range);
    return v;
};
Vector.distanceSquared = function(a, b) {
    var dx = a.x - b.x;
    var dy = a.y - b.y;
    return dx * dx + dy * dy;
};
Vector.distance = function(a, b) {
    var dx = a.x - b.x;
    var dy = a.y - b.y;
    return Math.sqrt(dx * dx + dy * dy);
};
Vector.prototype = {
    get x() {
        return this._x;
    },
    get y() {
        return this._y;
    },
    set x(value) {
        this._x = value;
    },
    set y(value) {
        this._y = value;
    },
    get magnitudeSquared() {
        return this._x * this._x + this._y * this._y;
    },
    get magnitude() {
        return Math.sqrt(this.magnitudeSquared);
    },
    get angle() {
        return Math.atan2(this._y, this._x) * 180 / Math.PI;
    },
    clone: function() {
        return new Vector(this._x, this._y);
    },
    add: function(v) {
        this._x += v.x;
        this._y += v.y;
    },
    subtract: function(v) {
        this._x -= v.x;
        this._y -= v.y;
    },
    multiply: function(value) {
        this._x *= value;
        this._y *= value;
    },
    divide: function(value) {
        this._x /= value;
        this._y /= value;
    },
    normalize: function() {
        var magnitude = this.magnitude;
        if (magnitude > 0) {
            this.divide(magnitude);
        }
    },
    limit: function(treshold) {
        if (this.magnitude > treshold) {
            this.normalize();
            this.multiply(treshold);
        }
    },
    randomize: function(amount) {
        amount = amount || 1;
        this._x = amount * 2 * (-.5 + Math.random());
        this._y = amount * 2 * (-.5 + Math.random());
    },
    rotate: function(degrees) {
        var magnitude = this.magnitude;
        var angle = ((Math.atan2(this._x, this._y) * PI_HALF) + degrees) * PI_180;
        this._x = magnitude * Math.cos(angle);
        this._y = magnitude * Math.sin(angle);
    },
    flip: function() {
        var temp = this._y;
        this._y = this._x;
        this._x = temp;
    },
    invert: function() {
        this._x = -this._x;
        this._y = -this._y;
    },
    toString: function() {
        return this._x + ', ' + this._y;
    }
}
/**
 * Particle Class
 */
function Particle(id, group, position, velocity, size, life, behavior) {
    this._id = id || 'default';
    this._group = group || 'default';
    this._position = position || new Vector();
    this._velocity = velocity || new Vector();
    this._size = size || 1;
    this._life = Math.round(life || 0);
    this._behavior = behavior || [];
}
Particle.prototype = {
    get id() {
        return this._id;
    },
    get group() {
        return this._group;
    },
    get life() {
        return this._life;
    },
    get size() {
        return this._size;
    },
    set size(size) {
        this._size = size;
    },
    get position() {
        return this._position;
    },
    get velocity() {
        return this._velocity;
    },
    update: function(stage) {
        this._life++;
        var i = 0;
        var l = this._behavior.length;
        for (; i < l; i++) {
            this._behavior[i].call(stage, this);
        }
    },
    toString: function() {
        return 'Particle(' + this._id + ') ' + this._life + ' pos: ' + this._position + ' vec: ' + this._velocity;
    }
}
// setup DOM
function simulate(dimensions, options) {
    // private vars
    var particles = [];
    var destroyed = [];
    var update = update || function() {};
    var stage = stage || function() {};
    var canvas;
    var context;
    if (!options) {
        console.error('"options" object must be defined');
        return;
    }
    if (!options.init) {
        console.error('"init" function must be defined');
        return;
    }
    if (!options.paint) {
        console.error('"paint" function must be defined');
        return;
    }
    if (!options.tick) {
        options.tick = function() {};
    }
    if (!options.beforePaint) {
        options.beforePaint = function() {};
    }
    if (!options.afterPaint) {
        options.afterPaint = function() {};
    }
    if (!options.action) {
        options.action = function() {};
    }
    if (document.readyState === 'interactive') {
        setup();
    } else {
        document.addEventListener('DOMContentLoaded', setup);
    }
    // resizes canvas to fit window dimensions
    function fitCanvas() {
        canvas.width = window.innerWidth;
        canvas.height = window.innerHeight;
    }
    // create canvas for drawing
    function setup() {
        // create
        canvas = document.createElement('canvas');
        document.body.appendChild(canvas);
        // correct canvas size on window resize
        window.addEventListener('resize', fitCanvas);
        // go
        go();
    }
    // canvas has been attached, let's go!
    function go() {
        // set initial canvas size
        fitCanvas();
        // get context for drawing
        context = canvas.getContext(dimensions);
        // simulation update loop
        function act() {
            // update particle states
            var i = 0;
            var l = particles.length;
            var p;
            for (; i < l; i++) {
                particles[i].update(this);
            }
            // clean destroyed particles
            while (p = destroyed.pop()) {
                do {
                    // has not been found in destroyed array?
                    if (p !== particles[i]) {
                        continue;
                    }
                    // remove particle
                    particles.splice(i, 1);
                } while (i-- >= 0)
            }
            // repaint context
            options.beforePaint.call(this);
            // repaint particles
            i = 0;
            l = particles.length;
            for (; i < l; i++) {
                options.paint.call(this, particles[i]);
            }
            // after particles have been painted
            options.afterPaint.call(this);
        }
        function tick() {
            // call update method, this allows for inserting particles later on
            options.tick.call(this);
            // update particles here
            act();
            // on to the next frame
            window.requestAnimationFrame(tick);
        }
        /**
         * API
         **/
        function clear() {
            context.clearRect(0, 0, canvas.width, canvas.height);
        }
        function destroy(particle) {
            destroyed.push(particle);
        }
        function add(id, group, position, velocity, size, life, behavior) {
            particles.push(new Particle(id, group, position, velocity, size, life, behavior));
        }
        function spray(amount, config) {
            var i = 0;
            for (; i < amount; i++) {
                add.apply(this, config());
            }
        }
        function debug(particle) {
            this.paint.circle(
                particle.position.x,
                particle.position.y,
                particle.size,
                'rgba(255,0,0,.75)'
            );
            context.beginPath();
            context.moveTo(particle.position.x, particle.position.y);
            context.lineTo(particle.position.x + (particle.velocity.x * 10), particle.position.y + (particle.velocity.y * 10));
            context.strokeStyle = 'rgba(255,0,0,.1)';
            context.stroke();
            context.closePath();
        };
        this.clear = clear;
        this.destroy = destroy;
        this.add = add;
        this.spray = spray;
        this.debug = debug;
        this.paint = {
            circle: function(x, y, size, color) {
                context.beginPath();
                context.arc(x, y, size, 0, 2 * Math.PI, false);
                context.fillStyle = color;
                context.fill();
            },
            square: function(x, y, size, color) {
                context.beginPath();
                context.rect(x - (size * .5), y - (size * .5), size, size);
                context.fillStyle = color;
                context.fill();
            }
        }
        this.behavior = {
            cohesion: function(range, speed) {
                range = Math.pow(range || 100, 2);
                speed = speed || .001;
                return function(particle) {
                    var center = new Vector();
                    var i = 0;
                    var l = particles.length;
                    var count = 0;
                    if (l <= 1) {
                        return;
                    }
                    for (; i < l; i++) {
                        // don't use self in group
                        if (particles[i] === particle || Vector.distanceSquared(particles[i].position, particle.position) > range) {
                            continue;
                        }
                        center.add(Vector.subtract(particles[i].position, particle.position));
                        count++;
                    }
                    if (count > 0) {
                        center.divide(count);
                        center.normalize();
                        center.multiply(particle.velocity.magnitude);
                        center.multiply(.05);
                    }
                    particle.velocity.add(center);
                }
            },
            separation: function(distance) {
                var distance = Math.pow(distance || 25, 2);
                return function(particle) {
                    var heading = new Vector();
                    var i = 0;
                    var l = particles.length;
                    var count = 0;
                    var diff;
                    if (l <= 1) {
                        return;
                    }
                    for (; i < l; i++) {
                        // don't use self in group
                        if (particles[i] === particle || Vector.distanceSquared(particles[i].position, particle.position) > distance) {
                            continue;
                        }
                        // stay away from neighbours
                        diff = Vector.subtract(particle.position, particles[i].position);
                        diff.normalize();
                        heading.add(diff);
                        count++;
                    }
                    if (count > 0) {
                        // get average
                        heading.divide(count);
                        // make same length as current velocity (so particle won't speed up)
                        heading.normalize();
                        heading.multiply(particle.velocity.magnitude);
                        // limit force to make particle movement smoother
                        heading.limit(.1);
                    }
                    particle.velocity.add(heading);
                }
            },
            alignment: function(range) {
                range = Math.pow(range || 100, 2);
                return function(particle) {
                    var i = 0;
                    var l = particles.length;
                    var count = 0;
                    var heading = new Vector();
                    if (l <= 1) {
                        return;
                    }
                    for (; i < l; i++) {
                        // don't use self in group also don't align when out of range
                        if (particles[i] === particle || Vector.distanceSquared(particles[i].position, particle.position) > range) {
                            continue;
                        }
                        heading.add(particles[i].velocity);
                        count++;
                    }
                    if (count > 0) {
                        heading.divide(count);
                        heading.normalize();
                        heading.multiply(particle.velocity.magnitude);
                        // limit
                        heading.multiply(.1);
                    }
                    particle.velocity.add(heading);
                }
            },
            move: function() {
                return function(particle) {
                    particle.position.add(particle.velocity);
                    // handle collisions?
                }
            },
            eat: function(food) {
                food = food || [];
                return function(particle) {
                    var i = 0;
                    var l = particles.length;
                    var prey;
                    for (; i < l; i++) {
                        prey = particles[i];
                        // can't eat itself, also, needs to be tasty
                        if (prey === particle || food.indexOf(prey.group) === -1) {
                            continue;
                        }
                        // calculate force vector
                        if (Vector.distanceSquared(particle.position, neighbour.position) < 2 && particle.size >= neighbour.size) {
                            particle.size += neighbour.size;
                            destroy(neighbour);
                        }
                    }
                }
            },
            force: function(x, y) {
                return function(particle) {
                    particle.velocity.x += x;
                    particle.velocity.y += y;
                }
            },
            limit: function(treshold) {
                return function(particle) {
                    particle.velocity.limit(treshold);
                }
            },
            attract: function(forceMultiplier, groups) {
                forceMultiplier = forceMultiplier || 1;
                groups = groups || [];
                return function(particle) {
                    // attract other particles
                    var totalForce = new Vector(0, 0);
                    var force = new Vector(0, 0);
                    var i = 0;
                    var l = particles.length;
                    var distance;
                    var pull;
                    var attractor;
                    var grouping = groups.length;
                    for (; i < l; i++) {
                        attractor = particles[i];
                        // can't be attracted by itself or mismatched groups
                        if (attractor === particle || (grouping && groups.indexOf(attractor.group) === -1)) {
                            continue;
                        }
                        // calculate force vector
                        force.x = attractor.position.x - particle.position.x;
                        force.y = attractor.position.y - particle.position.y;
                        distance = force.magnitude;
                        force.normalize();
                        // the bigger the attractor the more force
                        force.multiply(attractor.size / distance);
                        totalForce.add(force);
                    }
                    totalForce.multiply(forceMultiplier);
                    particle.velocity.add(totalForce);
                }
            },
            wrap: function(margin) {
                return function(particle) {
                    // move around when particle reaches edge of screen
                    var position = particle.position;
                    var radius = particle.size * .5;
                    if (position.x + radius > canvas.width + margin) {
                        position.x = radius;
                    }
                    if (position.y + radius > canvas.height + margin) {
                        position.y = radius;
                    }
                    if (position.x - radius < -margin) {
                        position.x = canvas.width - radius;
                    }
                    if (position.y - radius < -margin) {
                        position.y = canvas.height - radius;
                    }
                }
            },
            reflect: function(particle) {
                return function() {
                    // bounce from edges
                    var position = particle.position;
                    var velocity = particle.velocity;
                    var radius = particle.size * .5;
                    if (position.x + radius > canvas.width) {
                        velocity.x = -velocity.x;
                    }
                    if (position.y + radius > canvas.height) {
                        velocity.y = -velocity.y;
                    }
                    if (position.x - radius < 0) {
                        velocity.x = -velocity.x;
                    }
                    if (position.y - radius < 0) {
                        velocity.y = -velocity.y;
                    }
                }
            },
            edge: function(action) {
                return function(particle) {
                    var position = particle.position;
                    var velocity = particle.velocity;
                    var radius = particle.size * .5;
                    if (position.x + radius > canvas.width) {
                        action(particle);
                    }
                    if (position.y + radius > canvas.height) {
                        action(particle);
                    }
                    if (position.x - radius < 0) {
                        action(particle);
                    }
                    if (position.y - radius < 0) {
                        action(particle);
                    }
                }
            }
        }
        // public
        Object.defineProperties(this, {
            'particles': {
                get: function() {
                    return particles;
                }
            },
            'width': {
                get: function() {
                    return canvas.width;
                }
            },
            'height': {
                get: function() {
                    return canvas.height;
                }
            },
            'context': {
                get: function() {
                    return context;
                }
            }
        });
        // call init method so the scene can be setup
        options.init.call(this)
        // start ticking
        tick();
        // start listening to events
        var self = this;
        document.addEventListener('click', function(e) {
            options.action.call(self, e.pageX, e.pageY);
        });
    }
};
</script>



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