Let It Snow demo

From 4f38455cb3040dcb662f075bedb3f2c97980c8c1 Mon Sep 17 00:00:00 2001 From: Yaroslav Date: Thu, 13 Dec 2018 19:26:02 +0300 Subject: let it snow! --- letitsnow/snow.html | 42 +++++++ letitsnow/snow.js | 327 ++++++++++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 369 insertions(+) create mode 100644 letitsnow/snow.html create mode 100644 letitsnow/snow.js (limited to 'letitsnow') diff --git a/letitsnow/snow.html b/letitsnow/snow.html new file mode 100644 index 0000000..17f6672 --- /dev/null +++ b/letitsnow/snow.html @@ -0,0 +1,42 @@ + + + + + Let It Snow demo + + + + + +

+ + diff --git a/letitsnow/snow.js b/letitsnow/snow.js new file mode 100644 index 0000000..213b43e --- /dev/null +++ b/letitsnow/snow.js @@ -0,0 +1,327 @@ +/* +Let it snow JS v1.0.0 +Copyright 2018 Yaroslav de la Peña Smirnov +All rights reserved. + +Redistribution and use in source and binary forms, with or without +modification, are permitted (subject to the limitations in the disclaimer +below) provided that the following conditions are met: + + * Redistributions of source code must retain the above copyright notice, + this list of conditions and the following disclaimer. + + * Redistributions in binary form must reproduce the above copyright + notice, this list of conditions and the following disclaimer in the + documentation and/or other materials provided with the distribution. + + * Neither the name of the copyright holder nor the names of its + contributors may be used to endorse or promote products derived from this + software without specific prior written permission. + +NO EXPRESS OR IMPLIED LICENSES TO ANY PARTY'S PATENT RIGHTS ARE GRANTED BY +THIS LICENSE. THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND +CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT +LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A +PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR +CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, +EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, +PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR +BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER +IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) +ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE +POSSIBILITY OF SUCH DAMAGE. +*/ + +/* +### Happy holidays 2018, and happy new 2019! ### +### Felices fiestas 2018, y feliz año 2019 ### +### С праздниками 2018 года, и с наступающим 2019-м! ### +*/ + +// A class for the particles/snowflakes +function Particle(posx, posy, scale, flakeType, tradiusx, tradiusz, tDuration, lastT){ + this.posx = posx; + this.posy = posy; + this.scale = scale; + this.flakeType = flakeType; + this.tradiusx = tradiusx; + this.tradiusz = tradiusz; + this.tDuration = tDuration; + this.lastT = 0; +} + +// Let it snow! +function letItSnow(options){ + /* >>> Some parameters <<< */ + // > max_particles: Number of snowflakes on screen + // > base_speed: Base speed for snowflakes in pixels/second + // It is multiplied by the size of the snowflake so that + // snowflakes in the foreground fall faster than ones in + // the background to give a parallax effect + // > max_xspeed: Same as base_speed but for the x (horizontal) axis + var max_particles = + options.hasOwnProperty('max_particles') ? options['max_particles'] : 400; + var base_speed = + options.hasOwnProperty('base_speed') ? options['base_speed'] : 100; + var max_xspeed = + options.hasOwnProperty('max_xspeed') ? options['max_xspeed'] : 150; + var max_tradius = + options.hasOwnProperty('max_tradius') ? options['max_tradius'] : 10; + var max_tduration = + options.hasOwnProperty('max_tduration') ? options['max_tduration'] : 5000; + var interactive = options['interactive']; + + + // x and y size of the original snowflake in pixels + const BASE_SIZE = 9; + + var canvas = document.getElementById("snow"); + if (!canvas){ + console.log("There is no '#snow' canvas to draw on! Aborting..."); + return; + } + var container = canvas.parentNode; + var ctx = canvas.getContext("2d"); + ctx.save(); + var hor_speed = 0; + + // This will be populated with all the 'particles' (i.e. snowflakes) + // on the canvas + var particles = []; + var last = null; // previous timestamp + var requestedFrame; + + // The (quarter) paths for our different snowflakes + var paths = [ + function(){ + let sfquarter = new Path2D(); + sfquarter.rect(1,1,1,1); + sfquarter.rect(3,0,1,1); + sfquarter.rect(3,2,1,1); + sfquarter.rect(2,3,1,1); + sfquarter.rect(0,3,1,1); + sfquarter.rect(1,4,2,1); + sfquarter.rect(4,4,1,1); + return sfquarter; + }, + function(){ + let sfquarter = new Path2D(); + sfquarter.rect(2,2,1,1); + sfquarter.rect(0,2,1,1); + sfquarter.rect(2,0,1,1); + sfquarter.rect(1,3,1,1); + sfquarter.rect(3,1,1,1); + sfquarter.rect(0,4,5,1); + return sfquarter; + }, + function(){ + let sfquarter = new Path2D(); + sfquarter.rect(1,1,1,1); + sfquarter.rect(3,0,1,1); + sfquarter.rect(0,3,1,1); + sfquarter.rect(2,3,1,1); + sfquarter.rect(3,2,1,1); + sfquarter.rect(1,4,3,1); + return sfquarter; + }, + function(){ + let sfquarter = new Path2D(); + sfquarter.rect(1,1,1,1); + sfquarter.rect(2,2,1,1); + sfquarter.rect(3,3,1,1); + sfquarter.rect(3,0,1,1); + sfquarter.rect(0,3,1,1); + sfquarter.rect(1,4,3,1); + return sfquarter; + } + ] + // This array will be populated with the prerendered snowflakes + // (i.e. the canvases) + var snowflakeTypes = [] + + function randomMulti(){ + return Math.floor(Math.random() * 11)/10 + 0.5; + } + + function randomInt(max){ + return Math.floor(Math.random() * max); + } + + function resize(){ + // On window/viewport resize, get the new size of the container + // and accordingly resize the canvas, then reinitialize + canvas.height = parseInt(container.offsetHeight); + canvas.width = parseInt(container.offsetWidth); + try{ window.cancelAnimationFrame(requestedFrame); } + catch(e) {} + initParticles(); + } + + function updateHorSpeed(e){ + // Get the rectangle for our canvas + let rect = canvas.getBoundingClientRect(); + // Determine the mouse's x position relative to our canvas + let mx = e.clientX - rect.left; + let half_rect = canvas.width/2; + hor_speed = (mx-half_rect)/half_rect*max_xspeed; + } + + + function prerenderAll(){ + for (let i = 0; i < paths.length; i++){ + snowflakeTypes.push(document.createElement("canvas")); + prerenderSnowflake(snowflakeTypes[i], paths[i]()); + } + } + + function prerenderSnowflake(flakeCanvas, sfquarter){ + // Prerender the snowflake to optimize + flakeCanvas.width = BASE_SIZE; + flakeCanvas.height = BASE_SIZE; + var flakeCtx = flakeCanvas.getContext("2d"); + flakeCtx.fillStyle = "#ffffff"; + flakeCtx.save() + // Draw a path with one quarter of the flake + flakeCtx.fill(sfquarter); + // Translate to center rotate, return to origin and draw another quarter + // Repeat 3 times + flakeCtx.translate(BASE_SIZE/2, BASE_SIZE/2); + flakeCtx.rotate((Math.PI/180) * 90); + flakeCtx.translate(-BASE_SIZE/2, -BASE_SIZE/2); + flakeCtx.fill(sfquarter); + + flakeCtx.translate(BASE_SIZE/2, BASE_SIZE/2); + flakeCtx.rotate((Math.PI/180) * 90); + flakeCtx.translate(-BASE_SIZE/2, -BASE_SIZE/2); + flakeCtx.fill(sfquarter); + + flakeCtx.translate(BASE_SIZE/2, BASE_SIZE/2); + flakeCtx.rotate((Math.PI/180) * 90); + flakeCtx.translate(-BASE_SIZE/2, -BASE_SIZE/2); + flakeCtx.fill(sfquarter); + flakeCtx.restore() + flakeCtx.save() + } + + // Draw the snowflake on our main (visible) canvas + function drawSnowflake(particle){ + let turbulenceZ = particle.tradiusz*Math.cos(particle.lastT); + // Position correctly, and scale accordingly + ctx.translate(particle.posx, particle.posy); + ctx.scale(particle.scale+turbulenceZ, particle.scale+turbulenceZ); + // Also, change the opacity based on its size + // to give an effect of distance + ctx.globalAlpha = particle.scale/1.7+turbulenceZ; + preCanvas = snowflakeTypes[particle.flakeType]; + ctx.drawImage(preCanvas, 0, 0); + ctx.restore(); + ctx.save(); + } + + function getNewParticle(){ + // Randomly assign them a position and size and draw them + // on the canvas + let posx = randomInt(canvas.width); + let posy = randomInt(canvas.height); + let size = randomMulti(); + let tradiusx = randomInt(max_tradius)/10; + let tradiusz = randomInt(3)/10; + let tDuration = randomInt(max_tduration); + let lastT = randomInt(63)/10; + // Also randomly choose a snowflake type + let flakeType = randomInt(paths.length); + return new Particle(posx, + posy, + size, + flakeType, + tradiusx, + tradiusz, + tDuration, + lastT); + } + + function initParticles(){ + particles.length = 0; + ctx.save() + for (let i = 0; i < max_particles; ++i){ + let particle = getNewParticle(); + particles.push(particle); + drawSnowflake(particle); + } + // Request the first frame + requestedFrame = window.requestAnimationFrame(nextFrame); + } + + function nextFrame(timestamp){ + if (!last) last = timestamp; + let delta = timestamp - last; + // If more than 250ms have passed since last frame, it is assumed + // that the browser stopped calling back frames because the tab/page + // was in the background, thus this frame is ignored, and the last + // timestamp reset + if (delta > 250){ + last = timestamp; + requestedFrame = window.requestAnimationFrame(nextFrame); + return; + } + // Clear the canvas before redrawing the snowflakes + ctx.clearRect(0, 0, canvas.width, canvas.height); + for(let i = 0; i < max_particles; i++){ + let particle = particles[i]; + // Determine how much the snowflake should fall based on + // how much time has passed since the last frame, our base speed + // and how large is our snowflake + let fall = delta*base_speed*particle.scale/1000; + let wind = delta*hor_speed*particle.scale/1000; + let nt = delta*2*Math.PI/max_tduration; + particle.lastT += nt; + if(particle.lastT > 2*Math.PI){ + particle.lastT = particle.lastT - 2*Math.PI; + } + let turbulenceX = particle.tradiusx*Math.cos(particle.lastT); + let turbulenceZ = particle.tradiusz*Math.cos(particle.lastT); + particle.posy += fall; + particle.posx += wind+turbulenceX; + // If the snowflake has fallen out of our canvas' bounds + // redraw at the top + if (particle.posy > canvas.height+BASE_SIZE*particle.scale){ + particle = getNewParticle(); + particles[i] = particle; + particle.posy = -BASE_SIZE*(particle.scale+turbulenceZ); + } + // If it fell out of bounds horizontally, redraw at the left + // or at the right edge of the canvas + if(particle.posx > canvas.width+BASE_SIZE*particle.scale){ + particle.posx = -BASE_SIZE*(particle.scale+turbulenceZ); + } + if(particle.posx < -BASE_SIZE*particle.scale){ + particle.posx = canvas.width+BASE_SIZE*(particle.scale+turbulenceZ); + } + drawSnowflake(particle); + } + last = timestamp; + requestedFrame = window.requestAnimationFrame(nextFrame); + } + + // This will resize and initialize the canvas + prerenderAll(); + resize(); + + function stop(){ + try{ window.cancelAnimationFrame(requestedFrame); } + catch(e) { + console.log("Couldn't stop"); + console.log(e); + } + } + + // Update horizontal speed based on how far the mouse is from + // the middle of the canvas + if(interactive){ + console.log("Interactivity is on"); + document.addEventListener("mousemove", updateHorSpeed); + } + + //If the window is resized, resize the canvas accordingly + window.addEventListener("resize", resize); +} -- cgit v1.2.3