This is a good question, since tangents have several meanings in the world of animation, and particularly in computer animation. Tangents typically refer to an aspect of a key frame, in that they define how the computer should ‘in-between’ the frames that are not specifically defined by keys (known as “key frames”). Since computer animators do not draw each frame, tangents help keep animation control of the frames in between these special key frames. If something needs to ‘ease in’ to a key (imaging the height of a bouncing ball at the top of it’s arc), then the tangent may be flat. If the motion does an abrupt ‘about face’ (such as the height of the same ball when it strikes the ground and is sent back upward), then the tangent might be much sharper.
Tangents in this sense are absolutely critical... so I’m guessing that the question at hand doesn’t actually pertain to this sort of tangent.
What I think the question is referring to is something having to do with the arcs of motion. Arcs are a very important principle of animation, since many natural or organic movements are defined in terms of an arc. Very rarely do we move from point A to point B in a direct, straight line – it’s just not natural. Robots may move this way, but humans, or dogs, or blades of grass actually are much more likely to move in a fluid, arcing sort of way.
The term “tangents” in this area may be referring to an invisible line that something moving sort of ‘bumps’ into. Sometimes called “walls,” these imaginary boundaries can be seen in animation that may need with it’s arcs. I recall a shot I was working on in which a character swung his hands up over his head. Other animators pointed out that half way up the arc, the hand seemed to ‘bounce’ off a wall that wasn’t there. It turned out that my arc was actually move like a sideways “V” and once I noticed it, it was quite obvious, and quite distracting. Fixing it wasn’t exactly simple (sometimes the successive breaking of joints means that tracking down the source of the problem is tricky) but in the end I was able to clean up the arc, which improved the shot immensely.
Cleaning up arcs is a very important step of the final polish pass when animating, and it’s one of the things that can distinguish really really excellent animation from animation that is just ‘really good.’
Animation Mentor Staff