Table of Contents
Start Page » DEMoCap: Drag[en]gine Motion Capture » Object Behavior Properties: Grab Attach
Properties related to grabbing objects behavior. See GrabObject Object Class. Objects with this behavior define a spot where the actor can grab physics simulated bones of the parent object. GrabAttach does not work on parent objects without physics simulated bones. GrabAttach also does not work if the object is not parented to another object.
Objects grabbed using GrabAttach are attached using a temporary constraint with all linear degrees of freedom locked and all angular degrees of freedom unrestrained. This has the effect of pushing and pulling objects at the origin of the GrabAttach object disregarding actor hand orientation.
While grabbing the object the actor hand is modified using Inverse Kinematics to ensure it is located at the grab location even if the actor pulls further away or pushes closed than the physical constraints of the grabbed object allow. For example if the GrabAttach object is attached to a drawer and the rig bone of the drawer is constraint to the case of the drawer then the drawer can only move a certain distance outwards and inwards and not turn. If the actor grabs this object he can easily move his hand further away than he could if he pulled on a real drawer. The drawer would be restraint to not move further outwards but the actor hand would move away from the drawer which looks wrong and breaks the motion capture result. Using Inverse Kinematics the actor hand is pulled back to the grab spot on the drawer which ensures the virtual hand does not move away.
Bone
Defines the bone to grab in the parent object.
If bone is empty string the entire object is grabbed using a temporary constraint with all degrees of freedom locked and the above mentioned behaviors do not apply.
If a bone is selected a temporary ball point type constraint is used and the above mentioned behaviors apply.
The combo box shows the list of bones in the parent object or an empty list of the GrabAttach is not attached to a parent object. The list of bones can be incorrect at times. Click the Update button to update the list of bones.
Grab
Defines aspects of grabbing.
If the Immobile check box is checked the grabbed object does not move nor turn. This can be used for example for locked doors or drawers. The actor hand is subject to Inverse Kinematics and other grab parameters but the actor can not move the object.
If the Lock IK Rotation check box is checked the rotation of the actor hand is locked to the rotation it had at the time of grabbing the object. If unchecked the actor hand pivots across the grab spot (the origin of the GrabAttach object). In some situations this is undesirable, for example when grabbing a handle of a door or similar object. In this case it is better to keep the hand at the same orientation relative to the grabbed object.