I know what the problem is its not the math, it’s the amount of pixels in the shader texture that’s slowing it down. And on my game I get 30fps with 100 boxes with physics, but I only use the glow when holding one box so I don’t know about it on all of them, I hope the new version of codea will have some noticeable speed differences.
@Luatee yes I’m hoping for those speed improvements 
and the test I did was 150 objects with physics, all glowing at the same time
It runs at 20 fps, the glowing itself slows a little bit down tho, but nothing than that, and I don’t mind them slowing down a bit
@stevon8ter depending on the width you’ll get different speeds, if you use a width of 20 for all boxes it will be a lot slower.
@Luatee I noticed that, but there was a very small (and yes very small) slow down when using either 1 or 150 bodies
But I could have been misstaken at that time xD
Haha well I’m gonna see if I can improve it a bit tomorrow anyway hopefully make it a bit faster
It looks amazing in my app, and doesn’t bring down the FPS at all (I’m drawing around 20-30 settings the position every frame).
Which app is this on? And thanks, good to know it runs smoothly!
StackIt.
I look forward to seeing what you do with it 
@Luatee, now I’m just guessing here, but I’m pretty sure he is using it to outline the falling shapes.
It’s for the “glue” power up. I call it glue, but it’s really not. It’s much more fun.
@Luatee i would like to make heavy use of your glowline shader in my app, it looks and works great. Is that okay? I will add you in the credits if it ever goes further than my ipad.
Did you succeed to make a circle glowline shader? if so, I would be interested to play with it, even if it is slow.
@piinthesky sure, I have another one where the glow comes from the middle outwards, I forget if I edited the OP with that version or not, I made a few circle glow line shaders, some a bit faster than others but never the speed I’m looking for, I’d be happy to put it on they’re all free for use
Cool. I forgot to put you in the credits. Whoops!
You’re bad, I still haven’t managed to see what it looks like because of the errors on start up
A little late, but that looks really awesome! Thanks for sharing it…