¶AdnSimshape

AdnSimshape is a Maya deformer to produce facial simulation in the animation rig of an asset. Given a facial expression, the deformer is able to compute the activation of the vertices in order to emulate the changes in the rigidity of the skin. As result, the dynamics of the simulated skin mimic the behaviour of internal muscles contracting.

During simulation, the solver reduces the inertias of the vertices with higher values of activation, while it computes standard simulation in the vertices that are not activated. One of the key features of AdnSimshape is the ability to extract muscle information directly from the neutral geometry and the set of deformed geometries with the facial expressions using Machine Learning techniques.

¶How To Use

The AdnSimshape deformer is of great simplicity to set up and apply to a mesh within a Maya scene. The combination of a rest mesh, deform mesh and animated mesh allows the system to compute activation values which would drive the behaviour and inertias of the output skin mesh (simulated mesh).

To create an AdnSimshape deformer within a Maya scene, the following inputs must be provided:

• Rest Mesh (R): Mesh with no deformation or animation (optional).
• Deform Mesh (D): Mesh with deformation driven by the facial expressions (optional, only if muscle activations with AdonisFX Muscle Patches is required).
• Animated Mesh (A): Mesh with deformation driven by the facial expressions and animation result of the binding to the animation rig.
• Simulation Mesh (S): Mesh to apply the deformer to. This mesh can be the animation mesh or a separate mesh with no deformation nor animation.

When initially creating an AdnSimshape deformer, it is possible to add both a Simulated Mesh and a Rest Mesh, or only add a Simulated Mesh. The process to create an AdnSimshape deformer is:

1. Select the Rest Mesh (optional), then the Simulated Mesh.
2. Press the in the AdonisFX shelf or press Simshape in AdonisFX menu under the Create section. If the shelf button is double-clicked or the option box in the menu is selected a window will be displayed where a custom name and initial attribute values can be set.
3. A message box will notify that AdnSimshape has been created properly, meaning that it is ready to simulate with default settings. Check the next section to customize their configuration.

In order to add or remove any of the optional meshes, a set of menu items are exposed in AdonisFX menu > Edit Simshape. In that submenu, the options to manage each mesh type can be found. See Figure 1.

To add any of these meshes to AdnSimshape, follow a similar procedure to when first creating the deformer:

1. First, select the Additional Mesh. then the Simulated Mesh.
2. Press the corresponding menu element in AdonisFX menu > Edit Simshape.
3. A message box will notify that the action has been successful.

To remove any of these meshes from AdnSimshape follow this procedure:

1. Select only the mesh with AdnSimshape applied.
2. Press the corresponding menu element in AdonisFX menu > Edit Simshape.
3. A message box will notify that the action has been successful.

¶Attributes

¶Solver Attributes

¶Muscles Activation Settings

¶Time Attributes

¶Scale Attributes

¶Gravity

¶Advanced Settings

Stiffness Settings

Dynamic Properties

Collision Settings

Attraction Settings

Initialization Settings

Activation Remap

¶Debug Attributes

¶Connectable Attributes

¶Attribute Editor Template

¶Paintable Weights

In order to provide more artistic control, some key parameters of the AdnSimshape solver are exposed as paintable attributes in the deformer. The Maya paint tool must be used to paint those parameters to ensure that the values satisfy the solver requirements.

¶Debugger

To better visualize deformer constraints and attributes in the Maya viewport there is the option to enable the debugger, found in the dropdown menu labeled Debug in the Attribute Editor.

To enable the debugger the Debug checkbox must be marked. To select the specific feature to visualize, choose it from the list provided in Features. The features that can be visualized with the debugger in the AdnSimshape deformer are:

• Collision Constraints: For each vertex, a line will be drawn from the mesh to the closest point of a collider. The debug lines will only be displayed in case collisions are enabled and colliders have been set up.
• Muscle Fibers: For each vertex, a line will be drawn showing the direction of the muscle fibers. The debug lines will only be displayed in case muscle activations have been enabled with an AdonisFX Muscle Patches file.

Enabling the debugger and selecting one of these constraints will draw lines from the influenced vertices in the simulated mesh to their corresponding reference vertices.

¶Advanced

¶Muscle Activations

AdnSimshape can emulate the behaviour of facial muscles by computing the muscle activation directly on the vertices of the skin geometry. The activation of the vertices is an advanced and optional feature that can work in two modes: from muscle patches data or from plug values.

Generate Muscle Patches

The data required to generate an AMP file is:

• Neutral mesh: Rest mesh with a neutral facial expression.
• Target meshes: Set of deformed meshes representing facial expressions.
  • The number of vertices in the neutral and the target meshes must match with the number of vertices of the simulated mesh that will be used for the simulation.

The Learn Muscle Patches tool allows the user to generate the AMP file:

1. Open the Learn Muscle Patches UI. Using the shelf button or go to the Edit Simshape submenu from the AdonisFX menu and press Learn Muscle Patches UI.
2. Add the neutral mesh.
3. Add the target meshes. These geometries are the set of facial expressions produced by blendshapes or a facial rig.
4. Select the vertices on the neutral mesh that will be involved in the training for the muscle patches generation. If Add Selected is pressed with no selection, the tool will display a pop-up and inform that all vertices will be used for the learning process. This button has to necessarily be pressed to enable the execution of the learning process.
5. Browse or specify the destination AMP file.
6. Configure custom settings for the learning algorithm.
7. Press Execute.

Additional custom settings for the learning algorithm:

Debug Activations

AdnSimshape integrates a debug mode to visualize the activations during the simulation. If this mode is enabled, then AdnSimshape will display a map of vertex colors from black to red on the simulation mesh where the black color is mapped to no activation and the red color is mapped to maximum activation.

In order to toggle and untoggle the debug mode, follow these steps:

1. Stop the simulation.
2. Move to pre-roll time or start time.
3. Press or go to the Edit Simshape submenu from the AdonisFX menu and press Activations Debugger.

¶Colliders

AdnSimshape supports an internal collider that has to be bound to the rig and combined into a single object in order to mimic the internal structures. Colliders can represent structures like the skull or the teeth.

Add Collider

1. Select the collider object.
2. Select the mesh with the AdnSimshape deformer.
3. Press the AdonisFX Shelf > Add Collider Shelf Button or go to the Edit Simshape submenu from the AdonisFX menu and press Add Collider.

Remove Collider

1. Select the collider object.
2. Select the mesh with the AdnSimshape deformer.
3. Press the AdonisFX Shelf > Remove Collider Shelf Button or go to the Edit Simshape submenu from the AdonisFX menu and press Remove Collider.

Add Rest Collider

The use of rest collider is recommended when the pre-roll simulation is not computed and the initialization to the animated mesh is enabled (see attribute Initialize to Anim Mesh). In order to allow the solver to build consistent collision data in those cases, it is necessary to provide both the rest mesh and the rest collider in the same space.

1. Select the rest collider object.
2. Select the mesh with the AdnSimshape deformer.
3. Go to the Edit Simshape submenu from the AdonisFX menu and press Add Rest Collider.

Remove Rest Collider

1. Select the rest collider object.
2. Select the mesh with the AdnSimshape deformer.
3. Go to the Edit Simshape submenu from the AdonisFX menu and press Remove Rest Collider.