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Drawing fractals patterns with JavaScript canvas

Joined
Apr 9, 2018
Messages
781 (0.30/day)
This is an interesting programming project I did a few years ago when I was super interested in playing with code.
The "coolFractals" program was originally not mine (it was an example program included with Just Basic) but my idea was to port it to JavaScript.
Obviously the benefits of HTML is that the code can now be run on any computer using just a browser.
Anyone who's interested in experimenting with it, just copy the code into Notepad and save it with a ".html" extension.

'coolFractal.bas contributed by Rod
nomainwin
dim col$(12)
WindowWidth = DisplayWidth
WindowHeight = DisplayHeight
UpperLeftX = int((DisplayWidth-WindowWidth)/2)
UpperLeftY = int((DisplayHeight-WindowHeight)/2)
midx=int(WindowWidth/2)
midy=int(WindowHeight/2)
button #1, "Clear", [clear], LR, 50, 10
open "Fractals" for graphics_nsb as #1
print #1, "trapclose [quit]"

[clear]
print #1, "down ; fill black"

[draw]
'set up some random colors
for c=0 to 12
col$(c)=str$(int(rnd(0)*256))+" "+str$(int(rnd(0)*256))+" "+str$(int(rnd(0)*256))
next c

'set up some random starting positions
a=rnd(0)
b=0.9998
c=2-2*a
dots=12000
x=j=0
y=rnd(0)*12+0.1

'calculate and draw the points
for i=0 to dots
scan
z=x
x=b*y+j
j=a*x+c*(x^2)/(1+x^2)
y=j-z
xp=(x*20)+midx
yp=(y*20)+midy
print #1, "color ";col$(i/1000)
print #1, "set ";xp;" ";yp
next i
goto [draw]

[quit]
close #1
end

My updated version of the code for HTML:

HTML:
<!DOCTYPE html>
<html>

<body>

<canvas id="myCanvas" style="border:1px solid #000000">
</canvas>

<script language="javaScript">

//Variables
    var a;
    var b;
    var c;
    var x;
    var y;
    var z;
    var j;
    var dots;
    var xp;
    var yp;
    var i;
    var colors;
    var randomColour;
    var canvas = document.getElementById("myCanvas");
    var context = canvas.getContext("2d");

//Resize and fill in canvas
canvas.width = screen.width;
canvas.height = screen.height;
context.fillStyle = "#000000";
context.fillRect(0, 0, canvas.width, canvas.height);

//Run code immediately to remove timeout() delay.
    //Set up some random starting positions
        a = Math.random();
        b = 0.9998;
        c = 2 - 2*a;
        dots = 80000;
        x = 0;
        j = 0;
        y = Math.random()*12 + 0.1;
    //Calculate and draw the points
        i = 0;
        function draw() {
            if (i<=dots) {
                z = x;
                x = b*y+j;
                j = a*x+(c*(Math.pow(x,2)))/(1+Math.pow(x,2));
                y = j-z;
                xp = (x*20) + (canvas.width/2);
                yp = (y*20) + (canvas.height/2);
                context.fillRect(xp, yp, 2, 2);
                i++;
                setTimeout(draw);
            };
        };
        setTimeout(draw)
    timeout();

function timeout() {
        //Generate a random hex colour
            colors = ["#FF0000","#FFD700","#008000","#0000FF"]
            randomColour = colors[Math.floor(Math.random() * colors.length)];
            context.fillStyle = randomColour;
    setTimeout(function () {
        //Set up some random starting positions
            a = Math.random();
            b = 0.9998;
            c = 2 - 2*a;
            dots = 50000;
            x = 0;
            j = 0;
            y = Math.random()*12 + 0.1;
        //Calculate and draw the points
            i = 0;
            function draw() {
                if (i<=dots) {
                    z = x;
                    x = b*y+j;
                    j = a*x+(c*(Math.pow(x,2)))/(1+Math.pow(x,2));
                    y = j-z;
                    xp = (x*20) + (canvas.width/2);
                    yp = (y*20) + (canvas.height/2);
                    context.fillRect(xp, yp, 2, 2);
                    i++;
                    setTimeout(draw);
                };
            };
            setTimeout(draw)
        timeout();
    }, 6000);
}

timeout();

</script>
  
</body>
</html>

Screenshot:

132346
 
Last edited:
This is cool thanks for sharing.
 
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