Open the scene
You will find a polygonal head object with a neutral facial expression
head) and three other heads with a “mouth open” (
AU12) and “purse lips” (
Open the BCS user interface by executing the MEL statement:
If you have a shelf button with this statement and don’t want to type MEL
commands, you can press it instead.
AU27 and then
In the bcsUI, use “New BCS->Create BCS” to create the BCS
deformer node with
AU27 as first target.
The term “target” is not really applicable for BCS setups. It is just
used for easier understanding since these simple weight/dataPoint
relations behave like Blend Shape targets.
You can now select the
head object and click on
DPK_bcs1 in the
Channel Box in order to see the weight attribute for
Instead of selecting just
head, you could have selected
all three targets and
head before creating the BCS node. The result
would have been that all three targets were already added to the setup.
But now, we will use the remaining two objects to show how to add targets to
an existing BCS setup.
Select the objects
In the bcsUI, use “Data Points->Add Selected Objects” to create
two more weights for these shapes.
Delete the three (dataPoint) objects
AU27 from the scene. You can always bring them back by
double-clicking their dataPoint in the dataPoint list.
If you want, you can bring the weights into a different order. For more
information, see Reordering Weights.
When you set the weights
AU27 to 1, you’ll see that
they don’t mix very well.
The mix of
AU27 is very important for “Ohh” and
“Uhh” sound shapes, so let’s create a combination for correcting this mix.
In the bcsUI, select the weights
AU27 and do a
“right-click->Create Data Point”.
A new dataPoint will appear in the dataPoint list and a new object will be
in the scene.
Move the new object
AU18_AU27 to the side so that you can see it
You can now start moving vertices of
AU18_AU27 until you’re
satisfied with the result. Be sure to constantly check how the head
deforms when going from just
AU18 to the
As it is more efficient to work on just one side, you can use Mirror
Geometry to copy your edits on one side over to the other side. It has a
short section in this Getting Started chapter in 3.3 Using Mirror Geometry.
You might also want to look into the other helper tools, such as
Paint Deform and Toggle View for optimizing your
In case you don’t want to model yourself now, simply follow these steps:
Import the scene
Select the imported object
In the dataPoint list of the bcsUI, select the dataPoint
Choose “Data Points->Connect Object->Absolute”.
Delete the object
AU18x27 from the scene.
The result should now look similar to this:
For the combination
AU12*AU27, you can proceed just like explained
above. The finished combination shape can be imported from the file
This combination is particularly suitable for demonstrating “Tweak Mixing”.
For an even more advanced and powerful setup technique, see
4.6 Making Use of the ACS.
Create the combination dataPoint of
Delete the created object
AU12_AU18 from the scene.
With the dataPoint
AU12*AU18 selected in the list, choose
“Extras->TweakMix…”. A new window will appear where you can
“remix” the dataPoint.
Set the slider for
AU12 to about 0.75 and the slider for
AU18 to about 0.666.
Delete the object
AU12_18 from the scene.
Not all combinations of weights that don’t look good have to be accounted for
in a BCS setup. Which combinations should be created depends on the facial
expressions the character needs for his performance, the personality of the
character and not least on the budget (setup time) of the project.
You can therefore decide for yourself whether this three-weight-combination is
necessary or whether you can get away with letting the animators be careful
how they animate your setup.
In any case, the scene
bcsSteps_AU12x18x27.ma contains this
combination shape, so that you can use the workflow described above to create
this combination dataPoint.
You can let the BCS create separate left and right versions of your modeled
target shapes. We will now demonstrate this with
If you want to skip the above steps, open the scene
Open the bcsUI (press the shelf button or execute the MEL statement
AU12 in the weight list and do a
Select the BCS node to see that there are now two values for
If you use one of them, you can see that the left-right separation is
You can tweak the falloff that is used to separate the two halves. To do
this, select the—now bilateral—dataPoint
AU12 and open the
There is a list of falloffs that is independent from the list of
dataPoints. Each bilateral dataPoint can use one of these falloffs.
When several dataPoints use the same falloff, editing this falloff
will affect all these dataPoints. This can lead to unexpected results
if you’re not aware of this fact.
Choose the falloff that seems best suited for separating this dataPoint.
For example, choose falloff “mid”.
In order to avoid any unexpected side-effects when editing the falloff,
you should copy this falloff so that only the dataPoint
it. To do this, simply click the Copy… button beneath the
falloff controls and enter a name, e.g. “AU12”.
With this independent falloff, you can safely try editing the actual
falloff curve to enhance the separation.
Note that the result of editing the falloff is subtle here since the
“mid” falloff wasn’t that bad in this case.
The last step is to assign this falloff to the remaining bilateral
dataPoints. Select the four combination dataPoints and choose “AU12”
from the falloff drop-down list.
A shows what happens when the tweaked “AU12” falloff is
assigned to the dataPoint
AU12 and the combination dataPoints still
have the “mid” falloff. In image
B, the bilateral dataPoints use
the “AU12” falloff too.
For manual vertex-level control over the left-right separation and/or to
create differing left and right versions, see 3.4 Tweaking the Left-Right Separation.
The result of following this tutorial can be found in the scene
You’ve now learned how to use the most important features of the BCS. On the
next pages, some of the other functions are presented with basic information
and little tutorials, which build upon the knowledge you’ve acquired here.