CAMediaTimingFunction with 3 {0.0f} Control Points?

Question

I'm trying to animate the alpha transitions of some NSViews. It needs to happen during another animation, specifically of it's superview (a bounds change). It's kind of complicated to explain why, but I need these alpha transitions to have a timing function wherein the alpha stays at 0.0 for the first 3/4 of the duration (0.25 seconds). I thought that if I defined my own timing function with the control points 0.0, 0.0, 0.0, 1.0, it would achieve the desired effect. Obviously, I don't understand timing functions specifically and math in general.

If anyone could provide some advice, that would be great!

Regards, Alec

Answer 1

The CAMediaTimingFunction creates a bezier curve using the control points. I think for this task a better solution would be to use keyframes for the opacity animation.

CAKeyframeAnimation *animation = [CAKeyframeAnimation animation];
animation.values = [NSArray arrayWithObjects:
                    [NSNumber numberWithFloat:0.0],
                    [NSNumber numberWithFloat:1.0], nil];
animation.keyTimes = [NSArray arrayWithObjects:
                      [NSNumber numberWithFloat:0.75],
                      [NSNumber numberWithFloat:1.0], nil];

Which will create an animation that stays at 0 until three quarters of the duration and then moves to 1.