# AS3 GlowFilter Efficiency Question

**URL:** <https://forum.kirupa.com/t/as3-glowfilter-efficiency-question/315196>\
**Category:** flash\
**Created:** [October 20, 2010, 1:27am UTC](https://forum.kirupa.com/t/as3-glowfilter-efficiency-question/315196 "2010-10-20T01:27:36Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![dgirons](https://avatars.discourse-cdn.com/v4/letter/d/e95f7d/32.png) [@dgirons](https://forum.kirupa.com/u/dgirons)\
**Post date:** [October 20, 2010, 1:27am UTC](https://forum.kirupa.com/t/as3-glowfilter-efficiency-question/315196/1 "2010-10-20T01:27:36Z")

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Hello,

I have searched the forums and I couldn’t find an answer to this question, so I apologize if this has already been explained somewhere.

I have a very large movie clip that represents a level in my game (2500 x 1800 px). Inside this clip is a single large vector shape representing the walls of a cave-like area.

Currently, I have the cacheAsBitmap property of this movie clip set to true and I can move through the cave in my game without issue. However, I want to apply a dark inner glow filter to this shape to give the appearance of shading on the walls. When I try to do this, my frame rate slows dramatically.

As I understand it, filters are automatically cached as bitmaps, so I believe that moving my clip across the x and y axes should not result in redrawing of the filter. I am only scrolling this clip, not scaling or rotating.

Could someone please explain to me why moving a clip with a filter applied is so much more memory intensive than without? Shouldn’t cacheAsBitmap make the overhead equal for both cases? Can anyone suggest a solution to this issue?

Thanks very much