Smoothly expanding sprite

How would you do this? I don't mind how it's implemented as log as it looks good (although bonus points for using standard C2).

Need (on user action):

• a round (disc) sprite expands from 'zero' to say, 130px radius
• must be visually smooth
• must be quick (e.g. no more than 0.3 sec) to fully expand
• must be same speed on any device (this is for mobile)

Thanks!

You can use lerp()

[attachment=0:cpmjdla1][/attachment:cpmjdla1]

Thanks for that.. It's smoother than what I had and more consistent. I measure 0.22sec on pc (for comparison) and about 0.28sec on my slowest device.

I added dt to get it the same across devices, and a timer to check. edit: and x4 sprites because I need 4 at once.

[attachment=0:arlyby38][/attachment:arlyby38]

I had been playing with scale and even animation frames. Scale is jumpy and animation frames play back at different speeds on different devices.

You can set it up a bit different so it will take exactly 0.3 seconds to transition. Then you also could use qarp() or cubic() for a non-linear transition.

Here are some ideas:

ease in:

qarp(0, 130,130, self.t)

ease out:

qarp(0, 0,130, self.t)

Overshoot and fall back:

qarp(0, 200,130, self.t)

Thanks so much, I'd never think to use that. Will be checking it out asap.