Whoa! That's a little bit of a generalization that I'm not 100% in an agreement with. Tearing does NOT always happen. The AVM2 display engine is fast enough to update the screen in most cases so tearing does not occur. However this is entirely up to the performance capabilities of the host machine. In other words the faster the machine the less of a chance you have an experience tearing. If you run flash on a Pentium 2 then you will some artifacts. As proof you can download a 1024x768 image and use actionscript to move it across the screen and you will not notice any tearing ( of course it would be wise to set the image to use runtime bitmap caching ). The reason for this is that starting in Flash 8 Adobe is using OpenGL on the Mac to do the final blitting to the screen. Using OpenGL for this greatly improves performance on the Mac platform where artifact could be seen the most as compared to the windows version of the plugin which if memory serves me correctly uses Direct X(not sure about this though).
-sam On Jul 11, 2007, at 2:05 PM, Austin Haas wrote: > > No, we do have those problems in Flash. If you move a large image > horizontally across the screen, you will see tearing and there is > no way to fix it. The frame rate in Flash is not sync'd to the > refresh rate of the screen. > > Blitting just means combining pixels from one bitmap into another. > I suppose you could say that calling copyPixels() or draw() is > blitting. > > -austin > > -- > Austin Haas > Pet Tomato, Inc. > http://pettomato.com > > On Wed Jul 11 14:54 , Keith Peters wrote: >> Well it seems like true double buffering would be solving a >> problem we >> don't really have in Flash. I've also heard the term "blitting" be >> applied to this technique in Flash. There are a couple videos up >> on the >> fitc.ca site from the toronto 07 conference that discuss this. >> >> Austin Haas wrote: >>> Double buffering isn't about performance. It's about drawing the >>> next screen before the monitor does a vertical sync. The purpose >>> of double buffering is to avoid graphic issues like tearing and >>> shearing that occur when the screen is being updated at the same >>> time as it's being drawn. >>> >>> You can use two buffers to simulate the double buffer technique, >>> and there might be some performance gains there, and you might >>> reduce the chances of tearing/shearing, but calling that double >>> buffering would be an abuse of terminology, as that term already >>> has an accepted meaning. You would be misleading anyone who was >>> looking for a solution to the real problems that double buffering >>> is intended to solve. >>> >>> I'd really like to know if there are performance gains with this >>> technique in Flash. I thought that I tried it a while back, but >>> abandoned the idea after seeing no real gains. Does anyone have >>> any data or a live comparison? >>> >>> -austin >>> >>> >> >> >> _______________________________________________ >> osflash mailing list >> [email protected] >> http://osflash.org/mailman/listinfo/osflash_osflash.org >> > > _______________________________________________ > osflash mailing list > [email protected] > http://osflash.org/mailman/listinfo/osflash_osflash.org _______________________________________________ osflash mailing list [email protected] http://osflash.org/mailman/listinfo/osflash_osflash.org
