The section of the help you have quoted explains it quite well in technical 
terms, but you might be looking for a description which is a bit easier to 
understand, is that right?


The Filter option on this node can have two uses; setting it to NEAREST will 
give you similar speed results at lower quality, it will playback a hell of a 
lot faster than it will on BOX. I usually use this option for comping / testing 
and then switch it to box once I am either happy with the retime, or want to 
render.  the result will not be exactly the same but it will be very similar - 
great for previewing.

BOX will do something similar to an average or blend of frames. It's worth 
noting that it's not clever or adaptive like an optical flow based retime. 
Using this will give you double edges in some cases. If you're familiar with 
the dissolve node - imagine doing a 50/50 mix dissolve between 2 frames; that's 
kind of what the box filer is doing. 

NEAREST will literally pick the nearest frame to the one it needs. When you 
stretch a clip 10 frames can become 30 frames, and that means you have 
generated empty frames [which you don't have content for] BETWEEN  real frames 
[that you do have content for] these gaps are filled by making / fabricating 
frames by using frames either side of it as a hint. Nearest is dumb - this will 
literally say ' well the frame I need to make is closest to that one - I'll 
just use that one instead of trying to make one myself' This makes for a very 
fast but very choppy result.

Box has a bit more tact about it, that will try and blend between the frames 
either side by averaging them. If it is trying to invent one fabricated frame 
between 2 real ones (say you half the speed) it will take the two real frames 
eitherside of it and average them. 

NONE is a funny one, I've never used it unless by accident. It's looking for 
information upstream which can do the frame interpolation (where it invents 
frames it didn't have before) for it. I'd imagine you could use this for 
something generated in nuke, like a roto or a transform or other nodes which 
can concatenate translations etc. it will definitely not work on footage / 
plates or any other type of movie or image sequence, I'd imagine it would just 
give you the same result as 'nearest' would give when it can't get data from 
upstream to do the interpolation. Like I've said I have never used it in 
context so I don't know what kind of inputs it needs. 


It has to be said though, the retime node is not really that good for slowing 
down footage. In most cases an optical flow based method will give much better 
results, but this is an art in it's self. Artists mostly use the retime node 
not for changing the speed of a clip, but changing where the clip starts by 
using the input / output ranges and looping clips using the before and after 
attributes. If I ever find a retime in a comp I usually find that it's been 
used for this purpose.  


RickyDooodles



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