¶AdnRibbonMuscle

AdnRibbonMuscle is a Maya deformer for fast, robust and easy-to-configure tissue muscle simulation for digital assets. Thanks to the combination of internal (structural) and external (attachment and slide) constraints, this deformer can produce dynamics that allow the mesh to acquire the simulated characteristics of a ribbon with fibers activations to modulate the rigidity, and attachments to external objects to follow the global kinematics of the character.

The influence these constraints have on the simulated mesh can be freely modified by painting them via the AdonisFX Paint Tool or by uniformly regulating their influence via multipliers in the Attribute Editor. Besides the maps and multipliers there are many other parameters to regulate the muscle's dynamics and behavior to a wide array of options.

¶How To Use

The AdnRibbonMuscle deformer is of great simplicity to set up and apply to a mesh within a Maya scene. The way this deformer works is by applying simulation on top a mesh emulating a ribbon muscle which follows the dynamics of attachment points set as anchors. Those attachments mark the anchor points for the muscle, prepared to act as tendons, and will introduce a great part of the dynamics to the deformer.

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

• Targets (T): List of objects with which the simulated muscle will interact. The targets can be either transform nodes (e.g. rig joints, locators, etc) or geometries (e.g. bones). Providing a list of targets is optional on create. However, they are required to add attachment and sliding behaviors to the muscle. One or multiple targets are supported.
• Muscle Geometry (M): Mesh that the AdnRibbonMuscle deformer will be applied to.

Follow this steps to create an AndRibbonMuscle deformer:

1. Select the Targets (if any) and the Muscle Geometry in that order.
2. Press the button in the AdonisFX shelf or press Ribbon Muscle in the Solvers submenu from the AdonisFX menu. 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. AdnRibbonMuscle is ready to simulate with default settings. Check the next section to customize their configuration.

¶Attributes

¶Solver Attributes

¶Time Attributes

¶Scale Attributes

¶Gravity

¶Advanced Settings

Initialization Settings

Stiffness Settings

Override Constraint Stiffness

Mass Properties

Dynamic Properties

¶Debug Attributes

¶Deformer Attributes

¶Connectable Attributes

¶Attribute Editor Template

¶Paintable Weights

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

¶Debugger

In order 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 AdnRibbonMuscle deformer are:

• Attachments To Geometry: For each vertex with a geometry attachment constraint weight greater than 0.0, a line will be drawn from the mesh vertex to its respective geometry target closest point at rest.
• Attachments To Transform: For each vertex with a transform attachment constraint weight greater than 0.0, a line will be drawn from the mesh vertex to its respective transform target.
• Fiber Constraints: For each pair of vertices forming a constraint a line will be drawn. If the Triangulate Mesh option is disabled the debugged lines will align with the edges of the mesh polygons. If the Triangulate Mesh option is enabled the debugged lines will align with the edges of the underlying triangulation of the mesh.
• Muscle Fibers: For each vertex, a line will be drawn showing the direction of the muscle fibers. In addition, the colors of the fibers will be modulated given the Activation value by interpolating the Fibers Color and the Activation Color. This will allow debugging the activation of the muscle more precisely.
• Shape Preservation: For each vertex with a shape preservation weight greater than 0.0, a line will be drawn from each adjacent vertex to the opposite adjacent vertex.
• Slide On Geometry: If the Max Sliding Distance value is greater than 0.0, for each vertex with a slide on geometry weight greater than 0.0, a line will be drawn from the mesh vertex to the closest point on its respective geometry target.
• Slide On Segment: For each vertex with a slide on segment weight greater than 0.0, a line will be drawn from the mesh vertex to the closest point to its respective segment.

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

¶Targets

Once the AdnRibbonMuscle deformer is created, it is possible to add and remove new targets to the system. Targets that are transform based like joints and locators will be treated as transform targets. Targets that are mesh based will be considered as geometry targets.

• Add targets:
  1. Select the transform or mesh nodes (one or more) to be assigned as targets to the AdnRibbonMuscle.
  2. Select the mesh that has the AdnRibbonMuscle deformer applied.
  3. Press the button in the AdonisFX shelf or press Add Targets in the AdonisFX menu from the Edit Muscle submenu.
• Remove targets:
  1. Select one or more transform or mesh nodes that are assigned as targets to the AdnRibbonMuscle.
  2. Select the mesh that has the AdnRibbonMuscle deformer applied.
  3. Press the button in the AdonisFX shelf or press Remove Targets in the AdonisFX menu from the Edit Muscle submenu.
  4. Alternatively, if only the mesh with the AdnRibbonMuscle deformer is selected, when pressing the button, all targets will get removed (transform and mesh targets).

Targets can be any transformation nodes or meshes. On one hand, transformation nodes such as joints or locators are used to create attachments to their world transformation matrices. On the other hand, meshes are used to create attachments to geometry and slide on geometry constraints. Check A Simple Setup for more information on how to paint the influence maps for the mentioned constraints.

¶Slide On Segment Constraint

Additionally to all previously mentioned constraints, ribbon muscles can have an additional, optional constraint that can define a segment over which the muscle will slide.

• Add Segment:
  1. Select the transform nodes from which a segment would be created for the muscle to slide on.
  2. Select the mesh that has the AdnRibbonMuscle deformer applied.
  3. Press Add Slide On Segment Constraint in the AdonisFX menu from the Edit Muscle submenu.

• Remove Segment:
  1. Select one or more transform nodes that are assigned as segment anchors to the AdnRibbonMuscle.
  2. Select the mesh that has the AdnRibbonMuscle deformer applied.
  3. Press Remove Slide On Segment Constraint in the AdonisFX menu from the Edit Muscle submenu.
  4. Alternatively, if only the mesh with the AdnRibbonMuscle deformer is selected, when pressing Remove Slide On Segment Constraint in the AdonisFX menu, all segments will be removed.