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BlitMask slower than scrollRect on iOS, AIR 18

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I am building a complex app for iOS with long scrolling sprites.

Actually, using BlitMask instead of scrollRect on a large Sprite, on iOS iPad retina it destroys performance instead of improving it. Is it expected or am I doing something wrong?


Actually, the flow is as follows:

- create BlitMask once

enableBitmapMode() once



apply BlitMask.scrollY

apply BlitMask.scrollX





it works as expected, interaction is restored on motion complete, but performance is horrible... goes from 40fps to 3fps... I export in GPU mode.

Am I doing anything wrong? Or is it related to parsing a complex BMP in a retina display and uploading to the GPU?


thank you very much


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You're not calling update() or forcing it to recapture the bitmap on every frame, right? Yeah, my best guess is that it's just how AIR has to chug through all those pixels or something. As far as I can tell, there's nothing we can do in BlitMask to resolve that. 

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Thank you. No I am not calling update() since the original clip remains the same. Yes probably on a retina ipad the amount of pixels to be computed is just too much... I will stick to cacheAsBitmapMatrix + vectors. Thank you very much. Great job by the way.

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