StackOverflow2013

Note that there are some explanatory texts on larger screens.

plurals

PO
text
Body
copied!<p>You've already partially hit on your answer: <code>drawImage()</code> does indeed have finish-like behavior in that it forces all outstanding drawing commands to complete before it reads back the image data. The problem is that even if <code>gl.finish()</code> did what you wanted it to, wait for rendering to complete, you would still have the same behavior using it as you do now. The main thread would be blocked while the rendering finishes, interrupting the user's ability to interact with the page.</p> <p>Ideally what you would want in this scenario is some sort of callback that indicates when a set of draw commands have been completed without actually blocking to wait for them. Unfortunately no such callback exists (and it would be surprisingly difficult to provide one, given the way the browser's internals work!)</p> <p>A decent middle-ground in your case may be to do some intelligent estimations of when you feel the image may be ready. For example, once you have dispatched your draw call spin through 3 or 4 <code>requestAnimationFrame</code>s before you call <code>drawImage</code>. If you consistently observe it taking longer (10 frames?) then spin for longer. This would allow users to continue interacting with the page normally and either produce no delay when doing the draw image, because the contents have finished rendering, or much less delay because you do the synchronous step mid-way through the render. Depending on the intended usage of your site non-realtime rendering could probably even stand to spin for a full second or so before presenting.</p> <p>This certainly isn't a perfect solution, and I wish I had a better answer for you. Perhaps WebGL will gain the ability to query this type of status in the future, because it would be valuable in cases like yours, but for now this is likely the best you can do. </p>

Querying!

Guidance

An individual column

Larger individual text columns get their own page to allow for proper reading.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload