I've been outrageously startled today by how AE works. I've been using AE for over 7 years and feel I have a good grasp of how the application works. My previous understanding concerning time remapping pre comps is that if you were to stretch the time-remapping keyframes to lengthen it that the duplicate frames would in fact be duplicate frames. This is the same thing that would happen to video without frame blending or pixel motion blur turned on. I had the concept in my mind that when precomposing a bunch of layers, that they would be rasterized unless collapse transformation was enabled.
Yet today I needed to lengthen a pre comp with hundreds of keyframes and other pre comps in it by about 2x to get a feel for it being a lot slower. After Ram previewing I expected a very choppy slower render with many duplicate frames but in fact viewed a completely smooth render without and duplicate frames. Why did I not know this before? Googling how time-remapping affects a precomposition doesn't turn up very much helpful information.
Did perhaps some default setting change since CS6 to CC? I can swear I've witnessed duplicate frames from a pre comp with non-video animation before, thus leading to my understanding of how AE works.
Nope, nothing new. AE works on exact "fluid" time, hence any temporal operation based on a native feature will result in sampling the values with sub-frame precision with regards to everything that happens inbetween. Has been forever this way. If you need to quantize the motion you can of course always use the Posterize Time effect or the matching expression function.
or you could in the advanced tab in your precomp setting click on the check mark "Preserve frame rate when nested"
what it means it will preserve the frame rate of your precomp and separate it from your main composition so when you use time remapping
you will have the behaviour you were expecting.
this could be a true life saver feature in situations where you use time remapping on a precomp with footage or 3D sequence mixed with AE graphics (solids, shapes, text etc.)
and unless it is turned on, when you start shifting time - layers may not synchronize in time anymore :/