Partial Re-rendering

JavaScript performance comparison

Revision 13 of this test case created

Info

How much faster is it to render just the parts of the canvas that changed, compared to the whole thing?

Rendering a white dot that moves across a black background.

Preparation code

<canvas id="c" width="640" height="480">
</canvas>
<script>
  var canvas = document.getElementById('c');
  var context = canvas.getContext('2d');

  var HEIGHT = 100;
</script>

Preparation code output

Test runner

Warning! For accurate results, please disable Firebug before running the tests. (Why?)

Java applet disabled.

Testing in unknown unknown
Test Ops/sec
re-render whole scene (black rect)
for (var i = 0; i < canvas.width; i++) {
  context.fillStyle = 'black';
  context.fillRect(0, 0, canvas.width, canvas.height);
  context.fillStyle = 'white';
  context.fillRect(i, HEIGHT, 5, 5);
}
pending…
only render differences
for (var i = 0; i < canvas.width; i++) {
  context.fillStyle = 'black';
  context.fillRect(i - 1, HEIGHT, 5, 5);
  context.fillStyle = 'white';
  context.fillRect(i, HEIGHT, 5, 5);
}
pending…
re-render whole scene (clear rect)
for (var i = 0; i < canvas.width; i++) {
  context.clearRect(0, 0, canvas.width, canvas.height);
  context.fillStyle = 'white';
  context.fillRect(i, HEIGHT, 5, 5);
}
pending…

Compare results of other browsers

Revisions

You can edit these tests or add even more tests to this page by appending /edit to the URL. Here’s a list of current revisions for this page:

0 comments

Add a comment