Blendshape Fundamentals

Here’s the Create 3d Characters mascot with layered blend shape animation. This demo uses pure blendshapes, no other deformers or controls.
 

Here’s a more finished facial rig by Kent Trammel, the controls are just driving the blendshapes, most probably via driven keys or connections.
 

 
Blends are also super handy on super cartoony characters where regular rigging methods can be problematic. See me work through the belndshape setup of the professor after doing a simple joint rig for the jaw. Here I’m using the brave rabbit SHAPES plugin. Skip to 30mins 20sec.

 

Todays Class

Facial Blendshapes
Corrective Blendshapes for Deformation

 

IMPORTANT NOTE

This is a rather dated tutorial and still a good one for understanding blendshape fundamentals. For anything beyond the basic concepts I now use SHAPES 2 which has a free personal learning edition. This makes it a lot easier for most tasks here. Additionally I no longer use Mudbox for sculpting face shapes, as 2016 has full sculpt functionality. But I’d use much the same principles today, only now in Maya. This page will be updated.

 

BLEND SHAPES (Morph Shapes)

Blend shapes know as morph shapes in other programs are very easy to understand and use. So long as the topology is the same on multiple meshes the computer can tween/morph between shapes. Blend shapes have a variety of uses and are used all the time while rigging soft surface organic characters or shapes.

Blendshapes are most commonly used in facial expressions but we can also use them for corrective deformation as well.

1. Duplicate the same object multiple times to ensure we have the same topology and vertex numbers.
2. Tweak the vertices on the duplicated meshes, do not add extra vertices by cutting/extruding etc.
3. Name the meshes appropriately as their names will be used as sliders. Select the duplicated meshes first and the mesh we wish to deform last.
4. Go to Create Deformers > Blendshape (option box)
5. reset the settings for defaults, type the name of your blend node (or if you leave it blank it will come out as blendshape1) and hit apply.
6. Find the blendshape node in the attribute editor on the object and drag the attributes to morph the object.

*tip
In the channel box select the blend node and go (channel box menu) edit > select node. This will select the blend node itself so the mesh isn’t highlighted anymore.
 

Blend shapes are also additive which means multiple blends can be layered together for different effects.

We can add new blendshapes in the edit deformers menu
Edit Deformers > Blendshape > Add

It’s also good to note that the blendshapes are still directly linked to objects so it’s a good idea not to delete the blends if you like to tweak them later. Simply group all the blends and hide them in your scene with layers or by keying the visibility to off.
 

 

Creating And Animating Blendshapes in Maya

In the following demo we build a simple face duplicate it to make face shapes for the mouth, brow and eyes. Then Create the blend shapes and animate them to create a workflow similar to that of a more complicated face.
 

 

Mirroring Blendshapes

For mirroring blendshapes Left and Right I model symmetrically and split the left and right sides with this Jeff Rosenthals split blendshape script. Download and copy the txt into a shelf icon as a python script…
http://www.jeffrosenthal.org/split-blendshape-script/
 

Absymmesh is also great for mirroring if you’ve only tweaked one side and for tweaking blendshapes. absymmesh

 

Adjusting Combined Blendshapes

Sometimes when two blendshapes blend together they may not react in the correct fashion. We tweak this merged shape with the help of scripts. The one I use is

Corrective Blendshape Creator 2.0.1 (maya script)
 

 

Facial Blendshapes

Creating face shapes requires a good knowledge of the face and how it works. We can sculpt shapes based on muscles, expressions, pheonemes or other. The choice is really up to you and we can modify them later or add new custom shapes too.

I highly recommend reading Gary Faigins book The Artists Guide To Facial Expressions, it’s an excellent and very accessible introduction to understanding anatomy and expressions of the face.

At some stage I’ll try and put up a list of the common shapes I use. Big studios while working on realistic faces will often work off the FACS system by Paul Eckman. You can find more here…

For cartoony faces be creative, here’s a good source of face shapes on pinterest…

Another nice example of facial animation can be found here…
http://cgclay.blogspot.co.uk/2010/10/blog-post_7119.html

 

Notes on Facial Blendshape Creation

There’s a few important things to note about facial animation.

1. Separate the blendshapes for parts of the face, brows, eyes, mouth etc
2. Mudbox is a great program for sculpting blendshapes and is very easy to use with Maya. See below.
3. Separate blendshapes into left and right for asymmetry. We can make symmetrical blendshapes in Maya or Mudbox and then create left and right versions with scripts. See below
4. When two blendshapes mix together we may want to tweak the corresponding shape, we can use scripts to tweak this too.
5. Blend shapes work well in combination with other deformers in particular with joints eg for the jaw. Clusters, sculpt deformers, wrap deformers, lattices etc use what works best.

 

Using Mudbox For Blendshape Sculpting (Sculpt Layers)

Mudbox is a great tool for sculpting blendshapes, simply select your mesh and go File > Send to Mudbox.
 

If Send to Mudbox is giving errors install the latest service packs and for maya if there’s still problems export/import in the old skool method with objs as seen here…
 

 

Basic Sculpting in Mudbox

In Mubox only work on the base mesh level 0. Our main tools for facial shapes are

– sculpt tool
– grab tool
– freeze tool

– Symmetry: while in a sculpting tool, switch symmetry on in the tool settings (usually x)
– brush size (hold b click drag)
– brush pressure (hold m click drag)

– smooth (shift hold)
– invert (ctrl hold)

– unfreeze is shift + U
– invert freeze is shift + I

– Yellow Issues
To turn off the yellow face selection hit the “v” key and click on the grey to deselect, then click on your usual sculpting tool.
 

 

Creating Sculpt layers Demo

Sculpt Layers are the same as blendshapes in Maya.

– Select your object in the object list.
– Go to the Layers Tab and create a new sculpt layer.
– Rename it
– With it highlighted we are sculpting on that sculpt layer or blend shape
 

 

Editing Sculpt Layers

We can edit the sculpt layers to separate the eye from the mouth. we do this with Mask

In Mudbox it’s important to know the difference between mask and erase.

Erase will delete the sculpt layer permanently but with mask we’re non destructively painting out a masked area, much like channels in photoshop.
 

 

Inverting Masks in Mudbox

**Nice pro tip here.

At the end of this tutorial series when we return to Maya you’ll notice the cheeks don’t match nicely when the blendshapes are combined. To get around this we can invert the masked layer -100 and combine it with the original at 100%. That will invert the mask.
 

 

Exporting Back to Maya

To send the sculpt layers as blendshapes back to maya use

(Mudbox) File > Send to Maya > Preferences…
and check on
“Export Sculpt layers on current mesh level as Maya Blendshapes”

*Errors and Bugs
When we send to Maya we *should* have a blend node on our object. I usually like to use add to scene when I’m sending and not replace which is prone to error.

As you can see in the following demo, the blend node wasn’t created automatically as it should be, however all the shapes were sent so it was just an easy mater of manually creating the blend shape. The Send To Maya command also seems to kill my Maya hotkeys.

*If the Send to Maya doesn’t work at all, simply export/import as obj’s for each face shape.
 

 

Joint Based Facial Animation

Sometimes it can be handy to use joint based facial animations. A long time ago I wrote a tutorial for this in the making of the cane-toad video. These days we can mix splines with joints and blendshapes to create a large range of features in our faces.

Whilst joint based systems are great in certain situations, big floppy mouths etc. While starting off I highly recommend just sculpting good blendshapes. They are far simpler and will save a lot of time their often better too!

A simple method of using a joint based system is to use driven keys like blend shapes.

(demo)

And blendshapes can be combined with this system using the corrective blendshapes method too.

 

Corrective Blendshapes

Corrective blendshapes are super handy when our skinning is not perfect. Skinning will never account for flesh squashing and stretching so we can make nice correctives to have this all work properly.

The manual method in Maya is a bit of a pain. Luckily there’s a solution, unluckily we need to install a plugin. First here’s the manual way…

(manual demo)

The downside of manually correcting blendshapes is the sculpting process which is far from intuitive. Extract Deltas is aplugin for maya that allows us to sculpt/model on a regular object rather than the object in the default pose.
http://www.braverabbit.de/playground/?p=443

Beware there are a number of tutorials claiming that this can be done without a plugin using the parallel mode in the blend shape options and by combining two blendshapes with a -1 and +1. This seems to work on the surface but falls down when parent joints are rotated above in the chain.

 

Automating Corrective Blendshapes

We usually setup driven keys based on joint rotations to automate correctives. However in certain situations gimbal will cause this to break.

Some info on correctives…
http://williework.blogspot.com.au/2011/08/follow-up-on-corrective-shapes-for-maya.html

 

Pose Space Deformation

Gimbal being a problem that it is, we can’t reliably map corrective blend-shapes to euler angles of our joint rotations. Enter the Pose Space Deformer. This method uses vectors rather than euler rotations and is far more reliable. The downside is there’s little implementation in maya by default. However there’s some solutions coming online which I’m yet to research fully but look promising. Michael B Comet released a free plugin for Maya but by all reports it hasn’t been maintained well lately. And it seems like you can now do Pose Space Deformations without a plugin which is ideal as all animators will need to have the plugin installed.

Here’s a good overview here and he goes on to recommend the Michael B Comet plugin… not sure how old this post is. But it’s worth a read
http://www.tokeru.com/t/bin/view/Maya/MayaRigging#poseDeformer
http://www.tokeru.com/t/bin/view/Maya/MayaPoseDeformer

Here’s the old Michael B Comet page (tested up to Maya 8)
comet-cartoons.com/maya.html

Nowadays though this is one of the most promising tutes I’ve come across lately claiming on a method to do it without the plugin. I’m yet to research it but if it works I’ll try to do a tutorial in my style as this is a rather major area in deformation. Here’s the video to watch…

(Extra)

Skin weights copy tool.
http://www.braverabbit.de/playground/?p=915