The blend shape tool is a tool that will take exact duplicates of the original geometry that have been sculpted into a new shape and make a seamless transition between the two, I.E. blend. This has many different uses including muscle bulges but the most common is for facial expressions. It is a very simple tool and extremely powerful.
To begin create a new layer named facial expressions in you layer panel (Fig. 1).
Now you need to figure out how many expressions you need and make that number of duplicates of the head. If you have a character that is a single piece of geometry then you need to duplicate the entire character (Fig. 2).
NOTE: You can create extra duplicates that you can use later if needed so always plan for more than you figure.
Add the duplicates to the facial expressions layer.
Without adding any new points or spans, sculpt each head to a different expression and rename it (Fig. 3).
For my character I have 20 different blend shapes. I have full expressions like happy, sad, angry, excited, smile, frown, etc…. and even individual sculpts for each eye blink and mouth shapes for lip synching. It is up to you how many you will want to use. I also have a few non sculpted heads I can use for a blend shape now and sculpt later if I need.
NOTE: It is extremely important to name ALL blend shapes for easier animation later.
To create the blend shapes simply select all the duplicates, then shift click the original head.
Then go to Create Deformers > Blend Shape > option box (Fig. 4).
When the option box opens simply name the blend shape facial_expressions and hit create (Fig. 5).
You have now created your facial expressions blend shapes. We will test them and shortly go back to our rigging to create a controller for these.
Turn your facial expressions layer invisible so they are hidden. DO NOT DELETE THEM.
Go to Window > Animation Editors > Blend Shape and expand the window and you will see all your blend shapes with slide bars (Fig. 6).
Drag one slide bar or another to test your blend shape or you can even combine multiple sliders to create combinations.
Creating a Controller For Blend Shape Facial Expressions
This part will vary based on what blend shapes you created, if any, for your character. If you have no blend shapes skip this step. If you do have blend shapes I will cover how to create a controller for one then all you need to do is repeat the steps for the rest of yours.
Select the face_ctrl and go to Modify > Add Attribute and enter the following (Fig. 12).
Name: (name of your expression or facial movement)
Minimum Type: -10
Maximum Type: 10
Repeat this step for all of your facial expressions so when the face_ctrl is selected the will show in the channel box (Fig. 13).
We will now use set driven key, like earlier, to control our facial expressions. I am working with a happy face so I will be using that as an example.
Go to Animate > Set Driven Key > Set
With that window open, also open the blend shape editor by going to Window > Animation Editors > Blend Shape.
Select the face ctrl and press load driver in the set driven key window since this will control our expressions.
In the right side of the window select the first expression you will work with (happy).
In the blend shape window press the select button under your blend shapes then press load driven in the set driven key window.
On the right side of the window select the blend shape you will be working with (happy).
See figure 14 below for a full overview of this.
Press key in the set driven key window to set the default.
Select the face_ctrl in the set driven key window and in the channel box change the attribute (happy) to 10
Then in the blend shape window move the slide bar up for the expression (happy) to 1 and you should see your face change too.
Press key in the set driven key window.
See figure 15 below for an overview of the window.
You have just added that facial expression to our control.
Repeat these steps for the rest of your expressions.
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Author:poorhousefx Submitted: 2005-11-30 09:52:56 UTC Tags: Software: Maya Views: 116,976