In the previous movie, we completed Andrew's texture set by painting his hard hat and combining it with his tools.
Let's now jump ahead and focus on giving Andrew different facial expressions.
To create believable expressions, you need to deform the face in a way that simulates the facial muscles underneath the skin.
You can accomplish this by various means, such as skinning the head mesh to animated bones or motion capture markers.
In this case, you'll use Mudbox to sculpt variations of Andrew's head with different facial expressions,
and then bring them back to Maya to use as blend shape targets.
Select Andrew's head, hair, and other facial features.
Choose Send to Mudbox > Send as New Scene.
This creates an active link between Maya and Mudbox.
Notice that all the head's textures are pre-loaded in their respective channels.
Lock the eyes, tongue, and teeth to avoid selecting them by accident.
Now before you start sculpting, let's examine the basic concepts behind human expressions.
Any facial movement, from a subtle smirk to a dramatic exclamation, is the result of muscle contractions under the skin.
These muscles pull the skin in different directions, which creates a given expression.
Let's take a simple smile for example.
When you smile, the zygomatic major muscle pulls the mouth back towards the ear and underneath the cheek, which bulges as a result.
At the same time, the orbicularis oculi muscle contracts, causing the lower eyelid to rise up slightly over the eye.
So for Andrew's smile to look natural, you must match these elements.
Subdivide the head until you have enough faces to work with.
Create a new sculpt layer and rename it Smile.
Select the Grab tool and make sure Mirror is set to X.
Start dragging the corners of the mouth towards the ear,
then gradually adjust the rest of the mouth so the lips stretch naturally.
Turn on wireframe mode to help you visualize the distortion of the mesh as you sculpt.
You'll find that organic sculpting is a trial and error process.
Try different combinations of brush sizes, strengths, and falloff values to achieve varying results.
As a general rule though, you'll want to configure your brush so that each stroke blends into the next.
If the skin ever becomes too distorted, hold SHIFT to temporarily switch to the Smooth tool.
As its name implies, this lets you smooth out some rough edges as you sculpt.
Drag the sculpt layer's strength slider for a preview of Andrew's smile in action.
Now let's take care of the cheeks and lower eyelids.
Select the Bulge tool and set its strength to a value between 0 and 1.
Drag over the eyelid and cheek to add volume in these areas.
The more pronounced you make these deformations, the more intense the expression will be.
You will need to find the right balance between intensity and subtlety.
Keep in mind that while the smile primarily impacts the eye and mouth regions,
its effects also spread to surrounding areas like the nostrils and chin.
Use the Grab tool to pull these areas slightly, simulating natural skin stretch.
Using these techniques, continue sculpting new expressions, each on their own layer.
The more expressions you store on layers, the more combinations you can create by blending them together.
For example, here's an "evil grin".
As you've seen so far, it's important to maintain proper topology within your mesh to ensure that any expression you sculpt flows naturally.
If you need to modify the base head's topology, such as adding new edge loops or polygons,
you can use the active link between Maya and Mudbox to update your current work and avoid data loss.
First, turn off all expression sculpt layers. You'll see why soon.
Switch back to Maya and add some new edge loops around the eyes, mouth, and across the bridge of the nose.
First go to Edge mode and select the Insert Edge Loop tool.
Click and drag on an edge to position the new edge loop,
and release to insert it.
Repeat these steps to insert the other edge loops.
Go back to Object mode and delete history on the head.
Update the current Mudbox scene with the modified head.
When Mudbox detects two meshes with matching names, it automatically opens a Transfer Details window.
This feature scans for differences in the new head, and then applies them to your current one.
The Search Distance value determines how far from the target surface Mudbox should look for differences between the two meshes.
Since both heads occupy the same space, there's no need to look very far, so set Search Distance to 0.1.
If you had left any of the expression sculpt layers on, the geometry differences between the two meshes would have been greater.
and thus, a higher Search Distance value would have been needed.
In cases where transferring details becomes tricky, such as small crevices,
the Select Missed Regions option will identify these problem areas so you can clean them up afterwards.
Leave the remaining options at their default value and click Import.
Andrew's head is now updated with its new topology definition.
Let's send Andrew's new expressions back to Maya.
Turn on an expression sculpt layers to send over,
then select Send to Maya > Add Selected to Current Scene.
This sends the head as a new mesh, instead of overwriting the current one in Maya.
Mudbox asks if we want to send our head as is, or to send the base level.
Since we want Andrew's head to match the resolution of his body, click "Send base meshes instead".
Repeat these steps with each expression you want to send over.
Back in Maya, the new heads occupy the same space as Andrew's base head.
Move them aside to get a better look.
Rename each mesh to match their expression.
You can now use these heads as blend shape targets.
Select all the heads, making sure you select the base head last.
Select Create Deformers > Blend Shape [Option].
Name this BlendShape node "Andrew_facialExpression".
Make sure Origin is set to Local so that each head's offset position is not calculated in the blend shape node.
Click Create.
A blend shape node now connects all the heads together.
Select Window > Animation Editors > Blend Shape.
The Blend Shape editor displays all loaded blend shape targets and provides easy-to-use keying controls to animate their blending.
Go ahead and let Andrew express himself!