Straight Ahead and Pose to Pose

Straight Ahead and Pose to Pose are work methods for animators. They are possible answers for the “how do I animate?” question.

Straight Ahead

This is the oldest one. It means animating sequentially, creating pose after pose, frame after frame, "straight ahead", from the first to the last in a sequence.
Its main characteristic is that while animating one has considerable creative freedom to choose how and where each pose will be.

Pose to Pose

Following this workflow, the artist starts 1st blocking out (planning, sketching) a sequence, by defining the key poses in it and roughly estimating in which frame each of them should be. These poses, which are known as extremes, are created first.
The remaining, "transition" ones -- called inbetweens -- can be done automatically by software interpolation, but for acceptable results, in particular to apply the principles we're studying and to remove the mechanical look of computer animation, further work is needed.

Why

Straight Ahead

Good points:

• very open for creativity during the keyframing work;
• can result in more fluid and natural looking animation;
• done for all frames in a sequence it totally eliminates the use of computer interpolation;
• a talented artist in a good day can achieve very spontaneous and elaborate results;
• specially good for fast, wild actions;
• only after finishing the animator will know how the scene ended up.

Bad points:

• it's easy to come to dead ends, where work may have to be discarded and redone;
• hard to make the character respect "marks": be somewhere or grab something at a definite frame;
• hard to create strong poses, well staged, solid and appealing;
• the resulting set of keyframes will probably be complex and disorganized, hard to work with;
• only after finishing the animator will know how the scene ended up.

Some might also add: more work while animating.

Pose to Pose

Good points:

• more control over the results, easy to respect marks;
• less room for pitfalls;
• more work in less time;
• the created extremes (plus soundtrack) can be used as animatic for critique and corrections;
• with planning, there's a better chance to come up with elaborate poses and moves;
• done every N frames or so, results in a clean layout of keyframes, easy to work with;
• randomness is played down.

Bad points:

• easy to result in “robotic”, dull animation;
• less room for creativity while creating and keyframing poses;
• randomness is played down.