3.1 First Steps

Download the Example Scenes
Creating Your First BCS Node
Adding the Remaining “Targets”
The First Combinations
Automatic Left-Right Separation
Conclusion

Download the Example Scenes

Please download the following example scenes in order to follow this tutorial:
https://www.stargrav.com/bcs/scenes/bcsGettingStartedScenes.zip

Creating Your First BCS Node

Open the scene bcsSteps_start.ma

You will find a polygonal head object with a neutral facial expression (head) and three other heads with a “mouth open” (AU27), “smile” (AU12) and “purse lips” (AU18) shape.
Open the BCS user interface by executing the MEL statement: DPK_bcsUI;

If you have a shelf button with this statement and don’t want to type MEL commands, you can press it instead.
Select AU27 and then head.
In the bcsUI, use “New BCS->Create BCS” to create the BCS deformer node with AU27 as first target.

Note

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 AU27.

Adding the Remaining “Targets”

Instead of selecting just AU27 and 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 AU12 and AU18.
In the bcsUI, use “Data Points->Add Selected Objects” to create two more weights for these shapes.
Delete the three (dataPoint) objects AU12, AU18 and 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.

The First Combinations

AU18 and AU27

When you set the weights AU18 and AU27 to 1, you’ll see that they don’t mix very well.

The mix of AU18 and 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 AU18 and 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 better.
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 AU27 or AU18 to the combination.

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 workflow.

In case you don’t want to model yourself now, simply follow these steps:

Delete the AU18_AU27 object.
Import the scene bcsSteps_AU18x27.ma
Select the imported object AU18x27
In the dataPoint list of the bcsUI, select the dataPoint AU18*AU27.
Choose “Data Points->Connect Object->Absolute”.
Delete the object AU18x27 from the scene.

The result should now look similar to this:

AU12 and AU27

For the combination AU12*AU27, you can proceed just like explained above. The finished combination shape can be imported from the file bcsSteps_AU12x27.ma

AU12 and AU18

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 AU12 and AU18.
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.

AU12AU18AU27

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.

Automatic Left-Right Separation

You can let the BCS create separate left and right versions of your modeled target shapes. We will now demonstrate this with AU12.

If you want to skip the above steps, open the scene bcsSteps_startLeftRight.ma
Open the bcsUI (press the shelf button or execute the MEL statement DPK_bcsUI;).
Select AU12 in the weight list and do a “right-click->Bilateral”.
Select the BCS node to see that there are now two values for AU12. If you use one of them, you can see that the left-right separation is already working.

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 falloff settings.

There is a list of falloffs that is independent from the list of dataPoints. Each bilateral dataPoint can use one of these falloffs.

Note

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 AU12 uses 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.

Image 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.

Conclusion

The result of following this tutorial can be found in the scene bcsSteps_finished.ma

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.