Interpolation types
When defining an animation curve, generally, it follows one of three interpolation methods—constant, linear, or cubic. Cubic curves can be expressed using any cubic equation, such as Bézier curves (which is what Blender uses) or Hermite splines (which is what Maya uses). This book uses Hermite splines to represent cubic curves.
A constant curve keeps its value the same until the next keyframe. Sometimes, this type of curve is called a step curve. Visually, a constant curve looks as follows:
A linear curve interpolates between two frames in a linear fashion (that is, in a straight line). As you saw with the sampled curve approximation example earlier, if the samples of a linear track are close enough, it can start to approximate other types of curves as well. A linear curve looks as follows: