ios - Multisampling for drawing app -

i'm creating drawing ios application, , in need of smoothing lines being drawn user. i'm using multisampling normal.

for each time user moves finger, code :

1. create points make line , draw these points sampling buffer.
2. resolve sampling buffer.
3. the result buffer drawn canvas.

the problem when user have big canvas (e.g: 2048x2048), resolve process takes quite time it's causing drawing lag/choppy. resolve process resolve pixels in buffer, regardless whether pixels needs resolved or not.

i saw drawing app procreate, , draws smoothly no lag big canvas.

so, possible, don't know how that.

does have idea solution?

thanks.

just in case has same problem me, found decent solution :

1. create smaller sampling fbo purpose of drawing lines last point current point. use 256x256 buffer.
2. when drawing last point current point, use sampling buffer , resolve.
3. draw sampling buffer current layer.

the result not bad, no more lag. problem setting appropriate transform, matrix, etc quite hard.