StickerFace is an opensource project providing users with the set of scripts and plugins needed to rig, animate, and render cartoon-inspired facial expressions with Maya and VRay.
Built with earlier versions of Autodesk Maya in mind, StickerFace heavily relies on the hardware acceleration made achievable by Maya's Viewport 2.0, and achieves better performances than earlier implementations of Maya's native projection nodes.
StickerFace's core features are its CGFX shaders used to provide animators with previews of the final facial expressions at real-time rates. But besides these GPU-enhanced materials, StickerFace also comes with scripts facilitating their use at all the relevant steps of the production process :
Each aforementioned script or tool is presented to users via an intuitive GUI that can be invoked through Maya shelves for quicker access.
Developed at SUPAMONKS STUDIOS, StickerFace's source code has since been released as an opensource project under the LGPL3 license.
The StickerFace Git repository is available here.
The repository stores the entirety of the source code needed to build and manipulate all the entities required by the facial animation workflow, from auto-rigging scripts to dedicated VRay nodes used during rendering. Its folder structure splits into two distinct hierarchies:
VRAY_DLL_VERSION = 0x32501).
Once cloned or downloaded from the Git repository, StickerFace's Maya tools only requires a few additional installation steps:
MAYA_PLUG_IN_PATH environment variable.
stickerface_install.mel script file onto a running Maya.
Building the VRay plugin is slightly more involving, and in its current state, compiling its source code has a couple of requirements:
path.lua file (by setting the EIGEN_ROOT and VRAY_SDK_ROOT variables). The Visual Studio solution used to compile the VRay plugin is generated by running the following command:
premake5.exe vs2012
Finally, the path to your compiled binary vray_stickerface.dll must appear in the environment variable used by VRay when searching for plugins to load (VRAY_FOR_MAYA2015_PLUGINS_x64 when working with Maya 2015 for instance).
A face created with StickerFace consists in the collection of texture sprites whose layering and projection are executed by a CGFX material. All facial features are then represented by sprites drawn from a common sprite atlas. An atlas is an image file made of the juxtaposition of all possible sprites, aligned in a regular grid layout.
At a given time, the controller of each facial feature supplies the index of the sprite to be displayed. For easier use, it is possible to assign a different validity range and default value to each facial feature.
A face is made up of eleven facial features and three extra sprites that can be used to create richer expressions. It should be noted that, beside layer ordering, some sprites can only appear through others: Pupil and eyelid sprites are expected to lie inside the sprites dedicated to eyeballs and will be cropped otherwise.
Above lies an image showing the controllers associated with the different facial features, as well as the identifiers the StickerFace system uses to refer to them.
Using StickerFace to adorn a shape with a facial rig is a two-fold process:
The autorig wizard is summoned by clicking the 
icon on the Maya shelves. The following dialog shall appear:
This first window gathers all mandatory information for performing automatic facial rigging on a given shape, as well as a couple of optional controls. Here is the meaning behind its icons:
represents the asset and should always be associated with a relevant name.
stands for the shape the facial rig and sprites will be applied to. You initialize it from the selection by clicking the 
icon on the right.
for the spherical projection, 
for the cubic projection, 
for the planar projection. 
icon.
corresponds to the sprite atlas, whose path is specified by clicking the 
icon. The sprite atlas corresponds to a file image storing all sprite disposed in a regular grid layout.
designates the body texture, which is the texture that will appear below the projected sprites. Its mapping onto the surface is dictated by the texture coordinates assigned to the vertices of the geometry. Its path is specified by clicking the icon.
The lower half of the dialog is reserved for optional controls over the generated facial rig:
represents the source object of an optional parent constraint targeting the generated rig's root transform. It can be initialized from the selection by clicking the 
icon on the right. By default, a parent constraint involving the face shape's transform is created.
indicates which external attribute will serve as a dynamic global scaling factor on all of the sprite projections. By default, no such connection is created, but users can specify any scalar attribute from the selection for that purpose by clicking the 
icon and picking one of its eligible attributes.
Once users have provided the required information, clicking the 
icon on the bottom right corner brings the following dialog if a valid sprite atlas has been located:
This step is optional and skippable, but it greatly facilitates the specification of the information required for the sprite atlas to be correctly handled by the StickerFace system. It provides visual support for the specification of the following:
symbol.
Since the previous step is optional, all the information it sets can be subsequently modified if needed, either by editing the values of the attributes attached to the face_anim_root controller (index ranges and default values, as well as scaling factors) or the generated material itself (atlas grid resolution):
Finally, clicking the 
icon on the right bottom corner triggers the generation of the facial rig.
Worth noticing from the DAG object hierarchy output by the autorig procedure are:
face_anim_root, targeted by a parent constraint and storing many extra attributes relevant to riggers,face_anim_null group, inside of which the controller shapes live,The transform hierarchy contains different categories of subgroups, each with its specific purpose:
*_anim transforms are reserved for animating the sprites' projections,*_anim_null groups are used to adjust the sprites' projections onto the face shape prior animation in order to create a proper neutral expression,*_curve_null groups enable the repositioning of the controllers' shapes without altering the sprites' projections,*_connected_null groups are used internally by the system and are not supposed to be edited.
Once the wizard has been successfully run, a dedicated material has been assigned to the face geometry, animation controllers have been generated, connected to its attributes, and placed within a specific hierarchy of transforms (as well as in a separate selection set). The facial rig should be functional, but it is most likely that manual adjustments will be needed for it to be usable at the animation stage.
For better efficiency, editing the facial rig should follow a specific workflow:
Place the overall controller hierarchy at a decent distance to the face geometry by translating the face_anim_null group along the z-axis.
Calibrate the sprites' projections on the face by adjusting the *_anim_null groups' translation and scaling values.
Only after you obtained a proper neutral facial expression, can you adjust the controllers' positions independently of the sprites' projections, by tweaking the *_curve_anim groups' transforms.
*_anim controllers should have a transform value differing from the identity.
Each facial feature is associated with a controller. Its world position dictates where its corresponding sprite projects onto the face geometry, and one of its extra attribute stores the index that determines which sprite from the atlas should be displayed.
While keyframing the controllers' sprite indices could be done via Maya's attribute editor, the animation process can be made much smoother by using the sprite picker that can be invoked by clicking the 
icon from the Maya shelves.
For a given asset, the sprite picker straightforwardly lays out thumbnails corresponding to the sprites each of the asset's facial feature can display.
asset choicer. Asset detection is triggered by clicking the 
icon.
Scripts are also available to speed up some of the most frequent face edits:
brings the asset's face back to its default configuration.
mirrors the asset's facial expression.
and 
symmetrize the asset's facial expression.
Beside the controller hierarchy, running the StickerFace autorig triggers the creation of a proxy object.
This object is used as a bridge between the animation scene and the lighting scene. Each asset is associated with its own proxy object. This proxy object stores the animation curves of all the facial features' controllers as extra attributes, as well as the information mandatory for the later stages of the StickerFace system to work.
All the names of the proxy's attributes start with the smks_ prefix. This prefix is used when baking the animation scene in an Alembic file to filter out irrelevant attributes.
For rendering animated facial expressions from baked scenes, one must make sure the proxy objects of all involved assets, as well as all their extra attributes, have been properly saved in the Alembic file.
After importing their Alembic archives to a new Maya scene, users simply need to run the last wizard from the StickerFace toolbox that is accessible by clicking on the 
icon on the shelf. Upon invocation, it will attempt to locate as many proxy objects as possible in the scene, and interpret all the available information related to them. The wizard will display its findings via proxy cards as follows:
Among the recognized pieces of information are:
, , or
Users can manually trigger the proxy object detection by clicking the icon.
Applying gamma correction to input textures is usually necessary prior rendering. The wizard proposes to facilitate this process by automatically adding a gammaCorrect Maya node inside the shading network it generates. Its initial value can be directly set via the wizard in the text field next to the 
icon.
gammaCorrect Maya node generated by the wizard.
When using different sets of textures between the animation and rendering stages (e.g. different resolutions), the rendering wizard allows users to change paths for both the sprite atlas and the body texture. This can be done on an individual basis by clicking the icons beside all paths, or by globally remapping resource path hierarchies by clicking the 
icon.
Clicking the icon brings the following dialog that users can use to globally swap between file hierarchy roots:
represents the source folder whose path will be replaced in all texture filepaths. It is set by clicking the icon.
stands for the destination folder whose path will replace instances where the source folder's path appears in the texture files. It is set by clicking the icon.
icon.
Once all proxy objects have been detected, their gamma correction values set, and the paths of their resource textures possibly updated, users can click the 
icon to generate the shading network needed to render the StickerFace expressions with VRay.
vrayformaya plugin, along with all the VRay plugins the system can find in the process. For that reason, first executions can appear suspiciously slow.
Below is an example of a character rendered with StickerFace expressions using the VRay renderer:
face_anim_root group at the top of the controller hierarchy,
