Section 9: Nulls and Null Hierarchy:
Now you know the basics of bones and bone hierarchy.
Let’s take a look at what we can consider a close relative of the bone…
In addition to regular bones there is another type of bone called a Null.
Nulls look a little different than a regular bone in a Model window and in the PWS (as you can see in the image on the left.)
They also have slightly different characteristics…
The primary difference between a Null and a regular bone is that a Null can’t have any model geometry assigned to it like a bone can.
A secondary difference between Nulls and bones is that Null is much easier to translate once it is selected in an Action window. That is because the selectable area of an active null is much larger than that of a regular bone.
A Null can be created within a model (And will be found in the same “Bones” folder as a regular bone).
A Null can also be created while in an Action file or Choreography window separately. In this case the Null will not be associated with any models bone hierarchy (so it won’t be found in the model’s “Bones” folder).
You can also see lines intersecting the base of the Null. These represent the Null’s local axis.
Aside from those differences bones and nulls behave the same way.
So why use Nulls for some things instead of bone?
You don’t have to if you don’t want to but I find that nulls have certain advantages over bones when setting up a rig
- Nulls are easily identifiable in an Action window and PWS.
- Nulls are often used strictly as targets for constraints.
- Nulls are easily manipulated in an Action window (bones are as well but in a different way). Depending on the rigger’s preference, this makes the null a suitable option as a Parent to bones and, or branches of bones.
- They are useful in setting up your bone hierarchy in the PWS.
- They can be created and used in an Action or Choreography (for example: as targets for constraints that don’t need to be saved with a model).
Nulls can be created within a model and be placed in a model’s bone hierarchy just like a bone.
Nulls can be parents to other nulls and bones.
Nulls can be children to other nulls and bones.
Everything that we have learned about bones and bone hierarchy also applies to nulls in a model.
We’ll use nulls a little later in this series so don’t worry if the practical uses for them are not quite evident to you at the moment.