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Flash: More Efficient Blur filter Values

February 27th, 2009 by Luis

Last year during the development of a project where blur filters were used extensively we put into practice several tips and tricks to be able to render this visual effects quicker.

What caught my attention on top of everything was something really obviuos, in fact it is mentioned in the Flash documentation (I never read every single line), values that are a power of 2 (such as 2, 4, 8, 16 and 32) are optimized to render more quickly than other values.

Having this into account, the problem (a fairly common problem in systems programming) was to locate the "next highest power of 2", whenever I need the value to be dynamic.

Here there are a few AS3 algorithms to find the next highest power of 2:

PLAIN TEXT

Actionscript:

var powerOf2:int=1;
var val:int=456;
while ( powerOf2 <val )
{
trace(powerOf2 <<= 1);
}

PLAIN TEXT

Actionscript:

function nextPowerOfTwo( value_ : int ):int
{
value_--;
value_ = (value_>> 1) | value_;
value_ = (value_>> 2) | value_;
value_ = (value_>> 4) | value_;
value_ = (value_>> 8) | value_;
value_ = (value_>> 16) | value_;
value_++;
return value_;
}

PLAIN TEXT

Actionscript:

function nextPowerOfTwo( value_ : int ):int
{
return int(Math.pow(2,Math.ceil(Math.log(value_) / Math.log(2))));
}

This entry was posted on Friday, February 27th, 2009 at 10:22 am and is filed under AS3, Flash, Learnings. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.