Graphics Reference
In-Depth Information
You can use the control on the 3D view header to tell the manipulator which space to use. How is this
useful? Well, let's say that you have a model of a car and are using the manipulator to animate it. The car
slides around a turn, then takes off in a new direction. You would like to use the manipulator, but the
car isn't going to be moving along any of the global axes ( x or y ). It just needs to move straight ahead,
relative to the car. Setting the widget to Local mode then displays it so that the y axis always points
forward. No matter how the car is oriented, you know that LMB dragging on the widget's y axis will
move the car in the direction it is facing. There are other instances in which this becomes useful, and
we'll discuss them as we encounter them throughout the topic.
3D Cursor
When you're working in a word processor, you
have a nice, blinky cursor that tells you where new
letters will appear when you type them. Blender's
3D cursor is a cursor—in 3D! You can see what it
looks like in Figure 3.14 . When you add new
objects, they appear at this location.
The 3D cursor is positioned in 3D space by clicking
with the LMB. One click positions it relative to
your view. In other words, if you are in a front
view and click the LMB to set the cursor location,
it will change the cursor's x and z values. Its y value,
which in a front view is “into” and “out of” the
screen, remains the same. To change its y value, you
have to go into a side view. So, a precise positioning
of the 3D cursor requires two LMB clicks, one each
in a different view.
Figure 3.14   The  3D  cursor.
While it's nice to know where new objects will sprout in your scene, the cursor has a more important
use. It can act as a pivot point for scaling and rotation transformations. Examine Figure 3.15 , a simian
orrery. To achieve this positioning, you could of course use the G key and simply move the orbiting
monkey. If you wanted precision, though, it would be nice to be able to use the rotate command, but
with something other than the monkey's center point as the pivot. Enter: the 3D cursor.
Notice the pop-up menu that's expanded on the 3D view header in Figure 3.15 . It allows you to use
different ways of determining the scale and rotation pivot point. The two most commonly used are Bound-
ing Box (the default, comma key) and 3D cursor (period key). When the 3D cursor is set as the pivot
point, any rotations that are done (R key, transformation widget) use it's location as the center of rotation.
Likewise, scaling will be done toward or away from the cursor, depending on how you move the mouse
while transforming. The hotkeys for switching the pivot point are useful, but I wouldn't call them essential
for memorization. If you're eating this up, go ahead and add them to the list of things to try to remember.
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