Снег на HTML5 canvas
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<style> #canvas { position:fixed; top:0px; left:0px; z-index:-1; } </style> <canvas id="canvas"></canvas> <script> var canvas = document.getElementById("canvas"); var ctx = canvas.getContext("2d"); //canvas dimensions var W = window.innerWidth; var H = window.innerHeight; canvas.width = W; canvas.height = H; //snowflake particles var mp = 25; //max particles var particles = []; for (var i = 0; i < mp; i++) { particles.push({ x: Math.random() * W, //x-coordinate y: Math.random() * H, //y-coordinate r: Math.random() * 4 + 1, //radius d: Math.random() * mp //density }) } //Lets draw the flakes function draw() { ctx.clearRect(0, 0, W, H); ctx.fillStyle = "rgba(255, 255, 255, 0.8)"; ctx.beginPath(); for (var i = 0; i < mp; i++) { var p = particles[i]; ctx.moveTo(p.x, p.y); ctx.arc(p.x, p.y, p.r, 0, Math.PI * 2, true); } ctx.fill(); update(); } //Function to move the snowflakes //angle will be an ongoing incremental flag. Sin and Cos functions will be applied to it to create vertical and horizontal movements of the flakes var angle = 0; function update() { angle += 0.01; for (var i = 0; i < mp; i++) { var p = particles[i]; //Updating X and Y coordinates //We will add 1 to the cos function to prevent negative values which will lead flakes to move upwards //Every particle has its own density which can be used to make the downward movement different for each flake //Lets make it more random by adding in the radius p.y += Math.cos(angle + p.d) + 1 + p.r / 2; p.x += Math.sin(angle) * 2; //Sending flakes back from the top when it exits //Lets make it a bit more organic and let flakes enter from the left and right also. if (p.x > W + 5 || p.x < -5 || p.y > H) { if (i % 3 > 0) //66.67% of the flakes { particles[i] = { x: Math.random() * W, y: -10, r: p.r, d: p.d }; } else { //If the flake is exitting from the right if (Math.sin(angle) > 0) { //Enter from the left particles[i] = { x: -5, y: Math.random() * H, r: p.r, d: p.d }; } else { //Enter from the right particles[i] = { x: W + 5, y: Math.random() * H, r: p.r, d: p.d }; } } } } } //animation loop setInterval(draw, 33); </script> |
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