Skeleton Tab Overview

Golaem Crowd uses a dedicated animation engine, which can automatically retarget, blend and mix motions on any kind of morphology. To perform these features, the animation engine uses its own representation of characters and motions. The morphology of a character is stored in the Golaem Character File (*.gcha), which is used in Entity Type nodes during a crowd simulation. The Skeleton Tab allows to convert a Maya skeleton (joint hierarchy) into the Golaem Crowd skeleton format.

The Skeleton Tab is also the place where you can edit the character's physical properties, as well as more advanced features like bones excluded from the inverse kinematics computation (IK). For more information on these features, see the Character Maker Main Concepts page. Note that bones excluded from IK can also be defined for each Skeleton Mapping Node in the Main Workspace, along with roll bones


Golaem Character Maker - Skeleton Tab

The information shown in this tab is relative to the Character File displayed in the active tab of the Main Workspace. To start using the Skeleton Tab you have to either load a character file or load a skeleton from a Maya joint hierarchy (see below).

Loading a Skeleton (Maya Joint hierarchy)

You can access this feature through:

  • Skeleton Tab: Load Selected Skeleton button 

This command only works if a joint node is selected in Maya, otherwise a warning message will be displayed in Maya's Script Editor. Keep in mind that the joint hierarchy must comply with Golaem Crowd's Character Prerequisites.

The skeleton is built starting from the joint that is selected in Maya as root of the skeleton. In most cases, it's the top most joint in the hierarchy that you need to select. 

Once the skeleton is loaded according to the Detection Mode (see below), the skeleton bone hierarchy is displayed in the Skeleton view (see below) and in Maya's viewport through the Character Maker Locator node, allowing you to check that it was properly detected.

Reloading a Skeleton

The skeleton of an existing Skeleton Mapping can be reloaded without breaking the mapping. This is especially useful when creating Skeleton Mappings for different morphologies that have a similar structure. To access this feature, press the Load Selected Skeleton button when a Skeleton Mapping already exists. Three options are available (see image below):

  • Remap by name: the bones of the new skeleton are remapped by name. If there are any missing bones, a warning message that lists the missing bones will be displayed, allowing to either continue or create a new mapping
  • Remap by bone id: the bones of the new skeleton are remapped by id. If the skeleton hierarchies are different, a warning message will be displayed, allowing to either continue or create a new mapping
  • Create New Mapping: creates a new empty Skeleton Mapping from the selected Maya skeleton


Reloading a skeleton on an existing Skeleton Mapping

Once the remapping is done, it's also possible to change the Skeleton Options (see below).

Skeleton Options

The skeleton options allow to configure the general properties of the skeleton.

Skeleton Options
Skeleton Options

Detection mode

This parameter determines how to detect the skeleton pose from the joint hierarchy. Three modes are available:

Joint Orient

The skeleton detection process will only consider the joint orient values of each joint, but the transform values won't be used. For more information, see Maya's documentation: User Guide / Rigging / Character Setup / Character Setup Menus / Skeleton  / Orient Joint.

Bind Pose The skeleton detection process uses the bind pose (more exactly, it uses the maya skin clusters nodes). It is the pose used in the skinning process.
For more information about the bind pose, see Maya's documentation: User Guide / Rigging / Character Setup / Skinning / Bind pose
Current Values  The skeleton detection process uses the local values of the joints at the current time, as a combination of the "Transform Attributes" and the "Joint Orient"

The Detection Mode is taken into account when loading the skeleton from Maya, but can be changed afterwards as long as no Skeleton Mapping is done. The detected skeleton is considered valid if the skeleton pose displayed by the Character Maker Locator node closely matches Maya's joint display.

Character Axes

Up Axis

The character's up axis. It should be the character's vertical direction, usually from its feet to its head. In most cases this is Maya's Y axis. 

Front Axis

The character's front axis. It should match the character's front facing direction. In most cases this is Maya's Z, X, -Z or -X axis.

Use the Character Maker Locator node to check that the character axes were correctly set.

Warning: it is crucial to set the Character Axes correctly, otherwise Motions cannot be extracted and replayed correctly.

Character Axes
Character Axes

Ground Height

This is the height of the ground of the character in Maya world coordinates. The ground is represented by the Character Maker Locator node as a grey plane. It should be adjusted so that it touches the bottom of the character's feet geometry (which can be different from the bottom of the skeleton). The Ground Height is used by the animation engine to correctly adapt the feet to the ground.

Adjusting Ground Height
Example of a correct value for Ground Height

Automatic skeleton mapping

This command analyzes the skeleton morphology and detects the structure of the skeleton. It creates the matching nodal representation of the skeleton in the Main Workspace and maps it to the skeleton. The accuracy of the Skeleton Mapping depends on the skeleton morphology, some adjustments might be needed.

Due to the human morphology specificity (Two legs, two arms and one head), the automatic skeleton mapping process is especially accurate on biped skeletons.

You can access this feature through:

  • Skeleton Mapping Tab: Auto Compute Skeleton Mapping button
  • Character Maker Menu: Auto Compute Skeleton Mapping action in the Skeleton Mapping menu

This feature only becomes available once a skeleton is loaded. If a Skeleton Mapping is present, it will be replaced by the one computed automatically.

The Automatic Skeleton Mapping has the following parameters:

Auxiliary Detection Factor

This factor is only used on grasper Limbs, to detect the difference between auxiliary and extension bones in the case where additional bones (usually bones excluded from IK or roll bones) could prevent a correct detection. On the bone chain of a Limb or Effector node, if there is a bend with an angle greater than the mean bone chain bend angle increased by the Auxiliary Detection Factor (Bend Angle > Mean Bend Angle + Mean Bend Angle * Auxiliary Detection Factor), then the bones before this bend are detected as auxiliary bones, and the rest of the bones in the chain as extension bones (see image below).

Roll Max Angle

Bones in the middle of a bone chain that bend less than this angle are considered as bones excluded from IK, and thus they can be used as roll bones (see Character Main Concepts page).


Auxiliary Detection Factor: bone bend angle is great enough to detect an Auxiliary bone chain

Check skeleton mapping

This option allows to check the conversion of bones from the Golaem Crowd internal representation to the source skeleton.


Check Skeleton Mapping

To preview the conversion of the skeleton mapping, click on the Check Skeleton Mapping button. A slider changing the Limb Length Ratio appears and is

played to try different sizes for all your limbs. The result is exposed on the  Character Maker Locator.

Physics Properties

See the Bone Physics Properties section.

Skeleton view

This view displays the bone hierarchy of the character skeleton, as detected from the Maya joint hierarchy. Each bone matches a Maya Joint and has a Bone Id, which may be used in several behaviors: Look At Behavior, IK Behavior, Constraint Behavior. When selecting a bone in this view, it's also highlighted on the the Character Maker Locator node, and the Character Maker Node to which it is mapped (if any) is selected in the Main Workspace.

Sheleton View
Skeleton View

An icon displays the mapping status of each bone:

Unmapped Bone

The bone is not mapped

Bone mapped to Pelvis

The bone is mapped to the Pelvis

Bone mapped to Spine The bone is mapped to a Spine
Bone mapped to Limb auxiliary The bone is mapped to a Limb as an auxiliary
Bone mapped to Limb extension The bone is mapped to a Limb as an extension
Bone mapped to Effector auxiliary The bone is mapped to an Effector as an auxiliary
Bone mapped to Effector extension The bone is mapped to an Effector as an extension

Skeleton Mapping Nodes View

This view provides access to the nodes that are used to define the Skeleton Mapping. To use a node, drag and drop it into the Main Workspace

Skeleton Mapping Nodes view
Skeleton Mapping Nodes View

Pelvis Node Icon Pelvis

Defines the pelvis of the character. A valid Skeleton Mapping must have one and only one Pelvis node

Spine Node Spine Defines a spine of the character. A Spine must be connected to another Spine or to the Pelvis. The Skeleton Mapping can contain any number of Spine nodes
Limb Node Limb

Defines a limb of the character. A Limb must be connected to a Spine or to the Pelvis. The Skeleton Mapping can contain any number of Limb nodes

Effector Node Icon Effector Defines an effector of the character. An Effector must be connected to a Limb. The Skeleton Mapping can contain any number of Effector nodes

For more information on each node type, see the Main Workspace page.

Template Skeleton Mappings View

This view provides a list of available predefined Skeleton Mappings. To use a template, drag en drop it into the Main Workspace. This will create the node structure, and the nodes will then have to be mapped manually.

Template Skeleton Mappings View
Template Skeleton Mappings View

A template can only be used if the Main Workspace is empty (i.e. usually after loading a skeleton from Maya).

Biped Template

This template fits most biped humanoid characters. It uses two Limbs for the legs, each with one Effector for the toes, two Limbs for the hands, each with five Effectors for the fingers, and one Limb for the head. Once the Skeleton Mapping is created from the template, the node structure can be modified to fit specific character morphologies.

Biped Template Skeleton Mapping
Biped Template Skeleton Mapping

Quadruped Template

This template fits most quadruped characters. It uses four Limbs for the legs (two front legs and two back legs), each with an Effector, a Limb for the head and a Limb with an Effector for the tail. Once the Skeleton Mapping is created from the template, the node structure can be modified to fit specific character morphologies.

Quadruped Template Skeleton Mapping
Quadruped Template Skeleton Mapping

Roll Bone Parameters view

This view allows to define which bones are excluded from IK (see the Character Main Concepts page for more information on bones excluded from IK).

Advanced Skeleton View
Roll Bones Parameters View

The Skeleton Mapping should be finished before using this view, as the list of available bones depends on it. To exclude a bone from IK, select it in the combo box and click on the + button. The bone will be added to the list below. To remove bones from this list, select them and click on the - button. The pose displayed by Character Maker Locator may update if a motion is loaded. 

Squash And Stretch Parameters view

This view allows to define how the Squash'n Stretch ratios are applied to the scale of their related bone at rendering, and also in Render Previz display mode (see the Character Main Concepts page for more information on Squash'n Stretch).

Advanced Skeleton View
Squash And Stretch Parameters View

By default, a Squash'n Stretch ratio is applied uniformly on all axis of the related bone. To specify a particular distribution on a given bone, select it in the combo box and click on the + button. The bone will be added to the list below, with the value UNIFORM set for each axis. These specified axis are the axis of the bone local coordinate system, and the one displayed in bold is the axis closest to the bone direction (e.g. the vector from this bone to its child bone). Each axis must be applied any of these value (by double-clicking on it):

  • UNIFORM: Apply scale on this axis with value equal to the bone Squash'n Stretch ratio
  • INVERSE: Apply scale on this axis with value equal to the square root inverse of the bone Squash'n Stretch ratio
  • NO SCALE:  Do not apply scale on this axis (scale with a value of 1.0 in fact)

Example of Squash'n Strech axis distributions for a streched right arm animation

To remove a bone from this list, select it and click on the -  button. Default setup is then used for this bone, e.g. UNIFORM parameter for each axis.

Bone Physics Properties

The Skeleton Mapping Tab also allows to edit the physical properties of the skeleton, by clicking on the Edit Physics Properties... button . This opens the Physics Properties dialog. These properties impact the way characters react when using the Physicalize and Force behaviors.

It is advised to use the Ragdoll Maya Primitives to fine configure the physics properties of a character, as explained here.

Physics properties can be automatically computed by clicking on the 'Reset Physics Properties' button. This will reset both the physics shapes (disble physics shapes on extensions, configure size on other bones) and angular limits of the ragdoll (computed according to the IK plane configuration).

To reset the angular limits only, you can use the 'Reset Angular Limits' button instead.

Physics Properties Dialog

The Physics Properties Dialog allows to edit all physical properties of the Skeleton in a table view. To edit a physical property of a bone, double click the wanted value in the row matching the bone, change its value and then hit the Enter key or select another cell.

To edit multiple properties at the same time (usually the same property for multiple bones):

  • select the wanted cells by left click-dragging the mouse over them or by clicking on a column or by clicking on multiple cells using the Ctrl key to add or remove a single cell to the selection or the Shift key to add or remove a range of cells to the selection
  • double click on one enabled cell in the selection while holding the Ctrl key to avoid deselecting the other cells, change its value and hit the Enter key or select another cell to apply the same value to all the selected cells

Physics Properties Dialog
Physics Properties Dialog

Hide the unphysicalized bones by clicking on the Hide Unphyscalized Bones button.

Notice that the Physics Properties Dialog allows to sort columns value by clicking on a column header.

Parameters

Id Displays the id of the bone in the Skeleton. All the properties on the same row belong to this bone.
Bone Name Displays the name of the bone in the Skeleton. All the properties on the same row belong to this bone.
Physicalize

When enabled, the bone has a physical representation defined by all the other parameters, and takes part in collisions as a rigid body attached to the rest of the bone hierarchy. When disabled, the bone has no physical representation, thus it doesn't take part in the physical simulation. No property applies in this case. Physicalized bones have an impact on crowd simulation performance when using the Physicalize and Force behaviors, thus to increase performance you can disable this property for unneeded bones.

Auto Size When enabled, the size of the physical shape is computed automatically based on the bone length, otherwise you can enter the size of the shape manually
Half extents L/W/H

Defines the size of the physical shape using distances from the center of the shape to its borders, or half extents, on each axis - Length (L), Width (W) and Height (H). This means that the total size on an axis is twice the half extent. To see the changes in Maya's viewport, on the Character Maker Locator node, click the Apply button.

Shape

Shape of the physical representation. There are 4 possible shapes:

  • Cylinder / Box / Capsule / Sphere
    Cylinder Shape Shape Box
    Capsule Shape Shape Sphere
Use Mass Edit the Mass of the physical shape instead of the Density. You can only edit either the Mass or the Density of the shape, the other one is deduced using the volume of the shape.
Mass Mass of the physical shape, in kg. You can only edit either the Mass or the Density of the shape, the other one is deduced using the volume of the shape.
Density Density of the physical shape, in kg/m³. You can only edit either the Mass or the Density of the shape, the other one is deduced using the volume of the shape.
Restitution Ratio of energy restituted when colliding (between 0 and 1)
Friction Ratio of energy lost when sliding (between 0 and 1)
Linear Damping Ratio of linear velocity lost per second (between 0 and 1).
Angular Damping Ratio of angular velocity lost per second (between 0 and 1)
Joint Lower Limit X/Y/Z Lower bound of joint rotation around each axis in the joint's local coordinate system, relative to the skeleton pose (between -360° and +360°)
Joint Upper Limit X/Y/Z Upper bound of joint rotation around each axis in the joint's local coordinate system, relative to the skeleton pose (between -360° and +360°)
Color Color of the bone, can be used in Collision Triggers. The standard color to avoid collision is grey (128,128,128).

Blend Shapes

This view lists all the blend shapes that are connected to the joint hierarchy of the character. 


Blend Shapes view

Each blend shape line in the Character Maker represents a weight of a Maya blend shape node (see image below).

Blend Blend Shapes in the Skeleton Tab and its matching Maya blend shape node in the Attribute Editor

Blend Shapes are automatically detected when loading a Skeleton from a Maya joint hierarchy. To reset the Blend Shapes, use the Load Selected Skeleton button (see Loading A Skeleton).

To add one or more blend shape groups manually, select one or more blend shape nodes in Maya and click on the "+" button. They cannot be added twice. To remove a blend shape group, select it in the Blend Shapes view and click on the "-" button. 

Notice that during simulation (either in Behaviors, Channels...), Blend Shapes will be considered as Blind Data (see below).

Blind Data

This view lists all the float Maya attributes that will be stored along a Character.

It's important to notice that those attribute values will be stored as *blind* data. It means that, even if they will be handled, blended and exported by Golaem, they will not be automatically used at rendering time. It's the user responsability to make use of those (either connecting them to a Shader Attribute or using the Plug Output of the Simulation Cache Proxy).


Blind Data View

Blind Data needs to be manually added to the Blind Data text field in the form "mayaNodeName.mayaNodeAttribute" separated with "," (see image below):


Blind Data in the Skeleton Tab and the matching Maya attributes in the Attribute Editor

Advanced Parameters View

Conversion Preview View
Advanced Parameters

The conversion from the Golaem Crowd internal representation to the source skeleton internally uses an IK system for each limb. As an IK system is slow at runtime, the results of the IK system for different values are stored in a cache that is then used in real time instead of the IK system. The Use IK Cache checkbox and the Cache Configurations Count allows to change the configuration for this cache.

Note that the cache configuration is used only for visualization purpose: changing these values does not change the values that are used during the simulation.