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ioscore-graphicscalayer

How to Efficiently Draw Shadows on Numerous CALayers in iOS?

I've got some card games which use CALayers to draw individual cards. There can easily be 40 or 50 of them on the screen, which usually works fine.

I recently tried to turn on their shadows using the simple properties for CALayers:

theCardLayer.shadowOffset = CGSizeMake(3,2);
theCardLayer.shadowOpacity = 0.7f;

At that point, the program started getting really laggy. Fair enough; some of the docs said that the shadows could be CPU-intensive.

Any ideas for how to efficiently draw shadows on everything? They're all on the same CALayer in the same UIView, so I'm wondering if there might be a way to pull the mask of the layer or its UIView and shadow that, or something ...

Any functionality up to iOS5 is fair game.

Solution

  • At the very least, try setting your layer's shadowPath property. It can make shadow rendering significantly faster.