Enabling rough keyframes

Hello again,

I’m animating some things and I’ve noticed that the keyframes are very smooth (an object moving will start slow and get faster and then slow down again). How can I make the keyframes stay a constant speed?

In graph editor select the keyframes and press T to select the interpolation mode https://www.blender.org/manual/animation/editors/graph/fcurves.html
You can set the default interpolation mode in the User Preferences / Editing options

FYI . . . A key to understanding what’s going on here is to actually “look at the f-curves / IPO-curves.” These are the things that are actually driving Blender’s animation system, more-or-less behind the scenes.

You’ll see that they are Bezier curves which pass through certain “points.” (You see that there are several curves, one per channel in very-obvious groups, and that all of them pass through sets of points that are always vertically aligned.) Those “sets of points” are your keyframes: the curves will always pass exactly through each point, thereby “hitting the mark.”

The Y-value of each curve, along the X-axis that is time, defines the value of each animation parameter (X, Y, Z, or what-have-you) at that particular point in time … whether “precisely at a point” or, more importantly, “in-between.”

In-between those keyframes, the curves normally bend smoothly upward or downward after passing through a point, then bend again as they approach the next one. This is what automagically produces the “ease-in / ease-out” effect.

If you don’t want the curves to bend like that … if you want them to instead trace a direct line between points, thereby producing direct movement that doesn’t ease in or out … that’s what the change of interpolation-mode actually achieves. The curve still performs its stated function, but it is no longer “curved.” So, the motion no longer “glides to a start, then glides to a stop.”