Object and Animation Basics - Blender Foundations: The Essential Guide to Learning Blender 2.6 - page 45

settings, rotate the view, change the frame range, etc. The animation will loop and loop in the 3D view
until you press the Esc key or Alt-A again to stop it.
Let your own animation cycle several times, or watch the one from the Web Bucket if you're not actually
working in Blender at the moment. Analyze what's happening. As Suzanne descends in the first 20 frames,
she's rotating the whole time. This may not be what you would have expected. (If you did expect it,
good for you!) Ideally, we'd like to have Suzanne descend, then turn at the bottom and set off in a new
direction. Obviously that's not what is happening.
How would you go about something like this? First, you need to understand that the reason Suzanne
rotates while descending is because that is exactly what we told her to do. Animation isn't intelligent. Just
like any other aspect of computers, it will only do exactly what you ask of it. In this case, you told it to
use a certain rotation on frame 1, then another on frame 21, and to blend between those values in the
interim. Okay, you don't realize that you asked her to do that last bit, but you did. If a frame contains a
key, the value at the frame is obvious. However, between keyframes, Blender (and all other animation
systems) interpolates a value, based on the relative location between the keyframes and a number of other
factors.
Let's examine this interpolation in a very visual way. In Chapter 2 we talked about using different screens
for different types of work. Use the hotkey Ctrl-→ or Ctrl-← to switch to our next screen: Animation.
This screen, shown in Figure 3.19 , is mostly split between a 3D view on the right and a different screen,
called the Graph Editor , on the left. The curves on the left are a graphical representation of the way that
Blender interpolates between keyframes.
Tour time. Check Figure 3.20 for an expanded view of the Graph Editor. Each of the six curves in the
Graph Editor represents one of the axes and types of transformation of Suzanne. You can see the names
of these in the panel to the left of the curves: X Location, Y Location, Z Location, X Euler Rotation, Y
Euler Rotation, and Z Euler Rotation. If you had also keyframed Suzanne's scale, you would have three
more curves to deal with. Curves can be hidden and shown to clean up the view by enabling and disabling
the checkbox beside the curve's name. All of these animation channels can be collapsed on the left by
clicking the triangle icon to the left of the object's name. In Figure 3.20 , Suzanne's object name is “Mesh.”
The workspace of the Graph Editor is its own timeline. LMB drag in it, and you will see Suzanne go
back and forth throughout the steps you've animated. To get the hang of looking at a curve and actually
understanding what you see, examine Figure 3.21 . It shows an F-curve for an object that is animated
along the x axis—that is, moving left to right.
You read an F-curve from left to right, like a Western language, as it represents time. A flat portion of
an F-curve (B) means that the value is not changing over time. In this case, it means that between frames
30 and 50, the object is not moving along the x axis. A portion of the curve that slopes upward (C) means
that the value is increasing. An increase of the x axis value indicates motion toward the right. A downward
slope (A) indicates a decrease, or leftward motion along the x axis. The steeper the slope, the faster the
change. Curves (D) mean gentle transitions in motion, like a leaf soaring gently on the wind. Points (E)
mean abrupt changes, like running into a brick wall.