Collision spheres are added automatically to the feet nodes when you tag them—see Tagging the Foot Node.
In Behavior, an actor needs to have certain nodes tagged so that the simulation can be calculated properly. For example, Behavior needs to know which is the actor’s COG node, as well as its feet nodes. You need to initialize the character before tagging nodes.
In addition, you can add collision spheres to any node in the character to speed up collision detection in a Behavior simulation.
Sometimes a character’s COG node can have multiple siblings (all directly under the same GlobalSRT node); for example, the valid COG node contains the animating hierarchy, but sibling nodes can include end effectors, envelopes, and other extraneous elements like lights and cameras.
If this is the case, you need to explicitly set which node you want as the COG node for the character. If the COG node is the only child under the GlobalSRT node, you don’t need to explicitly set it as the COG.
To explicitly set the COG node
1. Make sure that the character is initialized (see Initializing the Character).
2. Select the node on the character you want to set as the COG.
This node cannot be more than two levels down in the hierarchy from the Model node; for example, the most likely hierarchy structure is that the GlobalSRT is a node directly under the model, and the COG node is a child of the GlobalSRT node (see Setting Up Your Character’s Hierarchy for Behavior).
3. Choose Node > Set COG from the Behavior toolbar.
COG node information is added to this node, and the COG node that you’ve selected turns red so that it’s easily identifiable.
To unset the COG node
1. Select the node on the character that you’ve set as the COG.
2. Choose Node > Remove COG from the Behavior toolbar.
The COG node description is removed from the node.
Behavior actors that have locomotion require their foot nodes to be tagged so that they can properly follow the terrain in a Behavior simulation. Behavior uses the foot information to modify the stride of an actor so that it tracks the surface upon which it is moving. In this case, the foot note is driven as the end effector of an IK chain during the simulation.
As a rule of thumb, the foot node should be the node that is the closest child of the major bones of the legs. For example, if the thigh and calf make up a two-bone leg, then the ankle bone (the first bone below the foot’s root) should be the foot node. The foot node can be the leg’s end effector or an explicit child of the calf bone.
For Behavior to properly modify the actor’s locomotion over a terrain, it performs collision checks to detect if the feet penetrate a surface or are floating over it at contact points. To speed up the process of collision checking, Behavior uses collision spheres to represent the contact region of the foot with the terrain.
When you tag a node as a foot node, two collision spheres are automatically added to the foot that approximate its shape. The spheres are added to the child node of the foot that is farthest forward and behind the foot node’s origin (for example, the toe and the heel). You can add as many collision spheres as you like to describe the foot contact region, but the more spheres you add, the more computation is required in the simulation.
You can also choose to not add collision spheres by default by pressing Shift when you choose the Set Foot command. You can then add collision spheres to the foot nodes at a later time—see Adding Collision Spheres.
To tag the foot node
1. Make sure that the character is initialized (see Initializing the Character).
2. Set the home (default) pose of the character (see Setting the Character’s Home (Default) Pose).
3. Select the node on the character you want to set as the foot (usually the first bone in the foot chain).
4. Choose Node > Set Foot from the Behavior toolbar to add foot node information and collision spheres to this node.
If you don’t want collision spheres to be added automatically, press Shift when you choose the Set Foot command.
An RTKEffector custom parameter set is created under the node, which marks this node as being a foot. As well, the node you’ve tagged as the foot turns red so that it’s easily identifiable.
To unset the foot node
1. Select the node on the character that you’ve set as the foot.
2. Choose Node > Remove Foot from the Behavior toolbar.
The foot node information is removed from the node. You can also choose to remove the collision spheres from the foot node at the same time.
To speed up the process of collision checking, Behavior uses collision spheres to represent and approximate the contact region of the actor’s nodes with elements in its environment, such as props or other actors.
You can add collision spheres to any body part of an actor to detect collision, such as the feet, the hands, the head, or the chest. For example, you can add a collision sphere to an actor’s hand to detect when the hand hits an obstacle—or another actor!
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Collision spheres are added automatically to the feet nodes when you tag them—see Tagging the Foot Node. |
You can add as many collision spheres as you like to describe a node’s contact region, but the more spheres you add, the more computation is required in the simulation.
To add a collision sphere
1. Make sure that the character is initialized (see Initializing the Character).
2. Set the home (default) pose of the character (see Setting the Character’s Home (Default) Pose).
3. Select the node on the character to which you want to add a collision sphere.
4. Choose Node > Add Col Sphere from the Behavior toolbar.
5. Set its Radius in the dialog box that appears.
After the sphere is created, you can translate it into the desired position and scale it to change its radius.
To remove a collision sphere
• Select it and delete it as you would any object in XSI.
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