General iOS graphics efficiency

I'm working on a simple program that has 500 "particles" that have an x and a y coordinate. They move around the screen and respond to touches. As I go past 500 particles the app starts running much slower. 开发者_如何学编程Using CPU sampler I discovered that drawing the particles is taking up the most CPU time.

This is the drawing code:

CGContextSetFillColorWithColor(context, [UIColor colorWithRed:red/255 green:green/255 blue:blue/255 alpha:1].CGColor);
CGRect rectangle = CGRectMake(xpos,ypos,9,9);
CGContextAddEllipseInRect(context, rectangle);
CGContextFillPath(context);

red,green,and blue are floats used to change the color of the particles based on their speed, but this isn't the problem.

This is how I was taught to use Quartz and it works just fine for most drawing, but this code is executed 500+ times and the game starts slowing down. I've run the program with CPU sampler with the drawing code commented out and there is hardly any CPU usage despite all the math going on in the background.

Is there a more efficient way to draw circles in iOS?

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You can try two different approaches to help speed up performance...

• Use prerendered UIImage/CGImage instead of points (won't give you the ability to change colors/sizes dynamically, but maybe you only need a limited range for your app)
• Use OpenGL, GL_POINTS

Quartz is generally slower than OpenGL especially for path based drawing from all the research I've done on the IPhone. Refer to the IPhone Dev forums and you'll see a general consensus about this.

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Making a layer (CALayer) for each particle might actually make sense. In general, doing drawing "yourself" in -drawRect: is the path to slowness on iOS. Avoid it if at all possible.