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2_velocity.html
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<!DOCTYPE html>
<html><head><meta charset="utf-8"><title>Skookum Labs</title></head><body>
<canvas id="surface" width="600" height="400"></canvas><pre><code>var ball = {
x: 300,
y: 200,
r: 15,
vx: 1,
vy: 0
};
|
// ...
|
ball.x += ball.vx;
ball.y += ball.vy;
</code></pre><script>// Version 1 - Velocity
var ball = {
x: 300,
y: 200,
r: 15,
vx: 1,
vy: 0
};
var canvas = document.getElementById("surface");
var ctx = canvas.getContext('2d');
setInterval(function() {
// Clear display
ctx.save();
ctx.fillStyle = "rgba(0, 0, 0, .3)";
ctx.fillRect(0, 0, canvas.width, canvas.height);
ctx.restore();
// Update ball (with Physics! =)
// 1 - apply velocity to position (vx -> x)
ball.x += ball.vx;
ball.y += ball.vy;
// Draw ball
ctx.save();
ctx.translate(ball.x, ball.y);
ctx.fillStyle = "#fff";
ctx.beginPath();
ctx.arc(0, 0, ball.r, 0, Math.PI * 2, true);
ctx.closePath();
ctx.fill();
ctx.restore();
}, 10);
</script></body></html>