Understanding Updating World Coordinate 

Hi, 

I'm fairly new to ARCore and OpenGL. 
This app is great and similar to what i'm trying to do. 

I don't understand how the coordinates are updated for each stroke in this app after you move around. I know `LineUtils.GetWorldCoords` gets you world coordinate from screen touch, but how do we keep track of that and keep updating them?

Any help would be very appreciated. 

Thanks, 

