I'm working on an iOS app that requires drawing Bézier curves in real time in response to the user's input. At first, I decided to try using CoreGraphics, which has a fantastic vector drawing API. However, I quickly discovered that performance was painfully, excruciatingly slow, to the point where the framerate started dropping severely with just ONE curve on my retina iPad. (Admittedly, this was a quick test with inefficient code. For example, the curve was getting redrawn every frame. But surely today's computers are fast enough to handle drawing a simple curve every 1/60th of a second, right?!)
After this experiment, I switched to OpenGL and the MonkVG library, and I couldn't be happier. I can now render HUNDREDS of curves simultaneously without any framerate drop, with only a minimal impact on fidelity (for my use case).
- Is it possible that I misused CoreGraphics somehow (to the point where it was several orders of magnitude slower than the OpenGL solution), or is performance really that terrible? My hunch is that the problem lies with CoreGraphics, based on the number of StackOverflow/forum questions and answers regarding CG performance. (I've seen several people state that CG isn't meant to go in a run loop, and that it should only be used for infrequent rendering.) Why is this the case, technically speaking?
- If CoreGraphics really is that slow, how on earth does Safari work so smoothly? I was under the impression that Safari isn't hardware-accelerated, and yet it has to display hundreds (if not thousands) of vector characters simultaneously without dropping any frames.
- More generally, how do applications with heavy vector use (browsers, Illustrator, etc.) stay so fast without hardware acceleration? (As I understand it, many browsers and graphics suites now come with a hardware acceleration option, but it's often not turned on by default.)