title: UIKit additive blending
body: <p>This has been asked before but I didn't find a satisfying answer yet. Is there really no way to set a blendmode for a UIView (that is, use GPU compositing to achieve the blending).</p>
  
  <p>There are some suggestions using CGContextSetBlendMode like here: <a href="https://stackoverflow.com/questions/3908160/draw-an-image-in-additive-blend-mode-without-using-opengl">Draw an image in Additive Blend Mode without using OpenGL</a> but all these solutions I stumbled upon so far seem to use drawing routines and as far as I understand (and as far as my performance measures hint to) this will do the blending on the CPU (and only afterwards upload it to an OpenGL texture for display).</p>
  
  <p>But afaik UIKit uses OpenGL to present the underlying CALayers, so it should be the easiest thing in the world to use separate blending modes right there.</p>
  
  <p>since IOS 5 there also seem to be some particle systems <a href="http://www.raywenderlich.com/6063/uikit-particle-systems-in-ios-5-tutorial" rel="nofollow noreferrer">http://www.raywenderlich.com/6063/uikit-particle-systems-in-ios-5-tutorial</a> that also support additive blending (and I doubt that this blending is implemented on the CPU) - so is there maybe by now a way to use additive (or other kinds of) blending when displaying UIViews?</p>