Smeegs Smeegs - 5 months ago 162
Javascript Question

Trying to create a confetti effect in html5, how do I get a different fill color for each element?

EDIT:

For anybody who is curious, here is the finished result.

http://jsfiddle.net/vxP5q/742/embedded/result/




I'm building off of the code I found in this link

http://thecodeplayer.com/walkthrough/html5-canvas-snow-effect

I want to make this more of a confetti falling effect than a snow effect, and I would need to make each element a different color. But it seems that the fill color is set for entire canvas at once.

Is there a way to specify a different fill color for each element or am I going about this the entirely wrong way?

Thanks

Update: Here is the finished product if anybody has a need for confetti

http://jsfiddle.net/mj3SM/6/

window.onload = function () {
//canvas init
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 = 200; //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() * 15 + 1, //radius
d: Math.random() * mp, //density
color: "rgba(" + Math.floor((Math.random() * 255)) + ", " + Math.floor((Math.random() * 255)) + ", " + Math.floor((Math.random() * 255)) + ", 0.8)",
tilt: Math.floor(Math.random() * 5) - 5
});
}

//Lets draw the flakes
function draw() {
ctx.clearRect(0, 0, W, H);



for (var i = 0; i < mp; i++) {
var p = particles[i];
ctx.beginPath();
ctx.lineWidth = p.r;
ctx.strokeStyle = p.color; // Green path
ctx.moveTo(p.x, p.y);
ctx.lineTo(p.x + p.tilt + p.r / 2, p.y + p.tilt);
ctx.stroke(); // Draw it
}

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,
color: p.color,
tilt: p.tilt
};
} 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,
color: p.color,
tilt: p.tilt
};
} else {
//Enter from the right
particles[i] = {
x: W + 5,
y: Math.random() * H,
r: p.r,
d: p.d,
color: p.color,
tilt: p.tilt
};
}
}
}
}
}

//animation loop
setInterval(draw, 20);


}

Answer

Try it like this: http://jsfiddle.net/vxP5q/

The JS:

window.onload = function(){
//canvas init
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
        color: "rgba(" + Math.floor((Math.random() * 255)) +", " + Math.floor((Math.random() * 255)) +", " + Math.floor((Math.random() * 255)) + ", 0.8)"
    })
}

//Lets draw the flakes
function draw()
{
    ctx.clearRect(0, 0, W, H);



    for(var i = 0; i < mp; i++)
    { 
        var p = particles[i];
        ctx.beginPath();
        ctx.fillStyle = p.color;
        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, color : p.color};
            }
            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, color: p.color};
                }
                else
                {
                    //Enter from the right
                    particles[i] = {x: W+5, y: Math.random()*H, r: p.r, d: p.d, color : p.color};
                }
            }
        }
    }
}

//animation loop
setInterval(draw, 33);
}

What I've done. Where the pixels are generated I've added an unique (random) color. Where the update is, I'm making sure the colors are changed and where its drawn I've changed it so that it will create an inuque path for each confetti item.