Question: Inbetweening "the Bluth Way"

[C. Siemens]

I recently came across this youtube video (http://www.youtube.com/watch?v=rK9QLruqrC8) and it reminded me of my animation training.

As I'm sure I have mentioned before, my clean-up & inbetween teacher at animation school used to work for Sullivan Bluth and one of the first advanced techniques he taught us was just that method: drawing connecting arcs between similar points on two different frames, measuring the required distance for the inbetween on those arcs and then registering the sheets using those marks to move the parts to be inbetweened closer together.

I've used the technique to good results.
Some time later, however, a Canadian TV animator taught me a similar technique - instead of drawing arcs and marking the inbetween position of certain points on them, he would trace three or four identical marks onto the keys and inbetween. He'd then place the key frames on top of each other so that the parts to be inbetweened were as closely as possible together. Then he'd use the marks on all three drawings to register the inbetween sheet to the keys, moving the volumes together in a way similar to the first technique.
I've also used that technique for TV animation and found it to be a little quicker than drawing arcs and measuring points on them.

(Wow, this sounds complicated without being able to show it, my apologies ...)

My question to to others who may have used both techniques is, is there a definite disadvantage to the latter method? I realise it requires a little more visual judgement but at least for TV it has brought me similarly good results ...

[Rodney]

Then he'd use the marks on all three drawings to register the inbetween sheet to the keys, moving the volumes together in a way similar to the first technique.

It sounds to me as if the technique being used here is a straight Triangulization which would help in placing the precise location of a new point. This also sounds similar to Don's technique of taking the drawings off the pegs and rotating them to find the correct point via the edges of the animation paper.


Here are the basic steps of Inbetweening from the Don Bluth Academy (http://www.donbluth.com/acdmy/PrcssALL.html#cleanup) write-up about clean up:
TEN SIMPLE STEPS TO A GOOD INBETWEEN
1.Look at the timing charts.
2.Roll the extremes and plot the arcs of the action.
3.Turn on the backlight and put the drawings in flipping order.
4.Now following the arcs and charts, build your foundation by drawing the shapes and the shapes between the lines.
5.Turn off the backlight.
6.Flip the drawings and build a solid 3 dimensional drawing on your foundation.
7.Put the drawings in rolling order and recheck the inbetween.
8.Turn on the backlight.
9.Shift the drawings off the pegs to check volumes and inbetween details.
10.Fix the final problems, using both the backlight and flipping.

In Step 9 this appears to be primarily a method of validating that everything is in the right place. So... analysis... to determine what and where to draw versus actually putting the lines in place. The first stage you mention (with flipping) would seem to be preferred for inbetweening for its spontaneity and speed?

All this is my very novice understanding of the process. I look forward to a correct interpretation. :)

[C. Siemens]

Yeah, that's basically the technique. However, I was specifically advised NOT to use the edges of the paper because if the sheets aren't all cut to exactly the same measurements your positioning will be off by milimeters. If instead you trace your own marks on the sheets by which you align them you're on the safe side.

[GdeSouza]

Yes. I know the technique as "shift & trace". It works best when the artist understands drawings, drag , volumes and arcs. There is a danger with this technique for the neophyte to just put lines between lines and forget they are inbetweening masses. Just a caveat. TV smaller screen especially at the old rez was more forgiving. Features? maybe they are more wary about this.

[C. Siemens]

Yes, they're both shift & trace but especially for doing even inbetweens I find the second method quicker. The guy who taught us shift & trace was head of cleanup at Bluth Ireland for a time so the method seems to have served him well back in those days. I'd still always do difficult thirds drawing arcs rather than eyeballing distances between tick marks. And of course there are many, many inbetween positions that need to be constructed thinking three-dimensionally rather than just tracing lines.

Actually, inbetweens is where my boss and I have different views - he says he doesn't care how beautiful or awkward the individual drawings look as long as the animation as a whole works.
I basically agree but I also feel that too many awkward drawings can and will affect a scene negatively. As Richard Williams put it, in the end keys and inbetweens share equal time on the screen, being exposed for either 1/24th or 1/12th of a second - so why not try and make ALL drawings look good?

[Rodney]

Interesting discussion.
I think I'm understanding.

I take it this 'shift and trace' methodology is completely different from 'trace back'? The first used to keep correct volumes (shapes that are still moving) while the second to maintain more exact, static (mostly unmoving) shapes?

[C. Siemens]

Well, yes and no. When you're doing tracebacks you trace a standstill motif instead of constructing it. Shift & trace is used to trace an image moving between keys.
You shift the keys so that what you trace as the inbetween is actually the parts on the keys moved closer together. What makes it tricky is that you still have to make the traced image work within the motion arc. Also, as GdeSouza pointed out, just mechanically tracing something can leave you with awkward-looking inbetweens. It works best for keeping volumes consistent in slow, subtle movements where there isn't much change between keys and where mistakes would show more clearly.

[GdeSouza]

Trace back is when like when a character is standing but his feet aren't moving so you trace back the same feet every drawing for the duration. The thing to do here is to trace back to the first drawing when the feet stop moving, for example. If you trace successively (each successive last feet drawn, for example) it can distort, grow or shrink.

But that seems to have been more practice in the camera days. Nowadays with infinite levels of animation, there is a tendency just to add those feet as a held cel. But I hate the way it freezes....even though the element is not supposed to be moving. But that's just it; we never really stop moving unless we are dead, so trace backs can keep the animation alive even when an element is to be virtually stopped.

Sometimes when you look at animation drawings you can sometimes see a note from the Key animator like "T.B. to H12".

I have not done traditional animation professionally for about 10 years btw, just to qualify where I am coming from.

@C. Siemens: I hear ya.

[C. Siemens]

I'd say held cels have their advantages but only if parts of a character stay still for, let's say, two seconds or more. If it's only about ten frames or so, yeah, do tracebacks even if it seems a bit of a chore. What I don't like about held cels is how they sometimes disrupt the animation flow - 'OK, I've animated up to the held pose but now I can't go on, I've got to take the ruff key first and separate the body parts. Also, later I need to put all the held cels on top of each other to be able to properly inbetween into the pose'. Plus, sometimes it won't become apparent until compositing that some held parts haven't been separated right.
But yeah, always traceback from the original drawing is very important. My first professional animation assignment required me to do one traceback of my characters' still poses all the time. It was because the animation was so limited they wanted the still poses to wriggle a little. Otherwise not much would've gone on on the screen for too long. And draw as accurately as I could, the tracebacks would always wriggle - I suspect it was because our compositing software didn't register scanned drawings to each other perfectly. I refuse to believe my hand was that unsteady. :o