# Pixl.js Conference Badge - Rotating Cube

This example turns Pixl.js into a name badge that displays `Your Name` and `Espruino`, with a rotating cube to the right of them.

Just change the text to whatever you want, upload to Pixl.js and you'll have an animated name badge. You could also modify the coordinates used in order to draw some other 3D shape.

With this animation running you should still be able to get over a day's worth of battery life with a CR2032.

## Source Code

``````// The background image (which we pre-render)
var background;
// rotation
var rx = 0, ry = 0;

// pre-render the background image
function createBackground() {
g.clear();
g.setFont8x16();
g.drawString("Your",0,5);
g.drawString("Name",0,22);
g.drawString("-- Espruino --",0,48);
g.setFontBitmap();
background = new Uint8Array(g.buffer.length);
background.set(new Uint8Array(g.buffer));
}

// Draw the cube at rotation rx and ry
function draw() {
// precalculate sin&cos for rotations
var rcx=Math.cos(rx), rsx=Math.sin(rx);
var rcy=Math.cos(ry), rsy=Math.sin(ry);
// Project 3D into 2D
function p(x,y,z) {
var t;
t = x*rcy + z*rsy;
z = z*rcy - x*rsy;
x=t;
t = y*rcx + z*rsx;
z = z*rcx - y*rsx;
y=t;
z += 4;
return [100 + 40*x/z, 32 + 32*y/z];
}

var a,b;
// -z
a = p(-1,-1,-1);
b = p(1,-1,-1);
g.drawLine(a[0],a[1],b[0],b[1]);
a = p(1,1,-1);
g.drawLine(a[0],a[1],b[0],b[1]);
b = p(-1,1,-1);
g.drawLine(a[0],a[1],b[0],b[1]);
a = p(-1,-1,-1);
g.drawLine(a[0],a[1],b[0],b[1]);
// z
a = p(-1,-1,1);
b = p(1,-1,1);
g.drawLine(a[0],a[1],b[0],b[1]);
a = p(1,1,1);
g.drawLine(a[0],a[1],b[0],b[1]);
b = p(-1,1,1);
g.drawLine(a[0],a[1],b[0],b[1]);
a = p(-1,-1,1);
g.drawLine(a[0],a[1],b[0],b[1]);
// edges
a = p(-1,-1,-1);
b = p(-1,-1,1);
g.drawLine(a[0],a[1],b[0],b[1]);
a = p(1,-1,-1);
b = p(1,-1,1);
g.drawLine(a[0],a[1],b[0],b[1]);
a = p(1,1,-1);
b = p(1,1,1);
g.drawLine(a[0],a[1],b[0],b[1]);
a = p(-1,1,-1);
b = p(-1,1,1);
g.drawLine(a[0],a[1],b[0],b[1]);
}

function step() {
// reset the contents of the graphics to
// our pre-rendered name
new Uint8Array(g.buffer).set(background);
// change rotation
rx += 0.1;
ry += 0.1;
draw();
// update the whole display
g.flip(true);
}

// pre-render the background image
createBackground();
// Start animation at 5fps (for reasonable battery life!)
setInterval(step,200);
``````

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