This is the place. It's HN! I have a strong suspicion that CGAffineTransform and its associated methods are calculated through the ARM NEON co-processor. I don

This is the place. It's HN! I have a strong suspicion that CGAffineTransform and its associated methods are calculated through the ARM NEON co-processor. I don't see anything in the documentation you provided that mentions the GPU. It _could_ be done in a vertex shader on the GPU, but looking at the API, the use of Rotation, Scale and Translation methods seems more consistent with it being done on the CPU or the CPU's floating point co-processor. Otherwise, there would be something equivalent to glBegin() or glEnd() to prep calls to update the uniforms for the shaders and render to the frame and render buffers, much like CA's transaction based API for animations - the block based API is similar, too.[1] Frankly, switching to a shader just to do rotation/scaling/translation is a bit much, and better left to the CPU in most cases. Andy Matsuchak of Apple claims that "When you implement drawRect or draw with CoreGraphics, you're using the CPU to draw, and that drawing will happen synchronously within your application. You're just calling some function which writes bits in a bitmap buffer, basically."[2] That is rendering. Unless you're confusing rendering with compositing layers, the act of blending several CALayers/UIViews together. The compositing bit is completely dependent on how you opted to draw your layers; some can be composited on the CPU, others on the GPU. I've listed all the ways that a layer can be composited on the CPU, it's just something to watch out for. [1] - I'll grant you that CA has an implicit animation API, but CA also has a much more elaborate system of keeping current state and projected state in place. CA has layer trees for each to avoid having to block the CPU and wait on the asynchronous GPU for results, which CG doesn't. [2] - http://robots.thoughtbot.com/post/36591648724/designing-for-ios-graphics-performance#comment-720533654 http://robots.thoughtbot.com/post/36591648724/designing-for-...