I'm building a drawing application that let's users annotate images and diagrams in a freehand style.
Not unlike a glorified MS Paint program, but there is heavy background processing going on.
Have there been studies done to quantify how fast "drawing" style interactions need to update in order to seem "smooth" to users? (It terms of both input lag and update rate)
I'll certainly bring in users for testing, but I'd like to know where to set the initial goal posts.
Update to clarify some points raised below:
Users will care about accuracy as tight as 1-3 pixels, so tight freehand drawing tool control is necessary.
"input lag" and "frame rate" are issues that both need to be addressed, but they are not the same.
Not a touch interface. Users would be using a regular mouse.