Evaluation of Virtual Grabbing/Manipulation Techniques

One of the defining features of immersive virtual reality is the ability to interact with objects in the virtual world in a natural manner. Usually this is achieved by using a real-world metaphor: the user simply reaches out his/her hand, grabs the object, and moves it around using body, arm, and hand motions.

However, this metahpor is lacking. Users can only manipulate objects within the arm's reach. To grab other objects, some travel technique must be used. Positioning large objects is difficult with this metaphor, since the user must be so close to them.

Therefore, other techniques are needed. We are researching techniques which allow grabbing/manipulation of local and remote objects, which provide complete control over object position and orientation, and which are efficient and easy-to-use. There are two main categories of techniques.

Arm-Extension Techniques

In this metaphor, the user's virtual arm can be extended or retracted to grab or position virtual objects. We have implemented and tested the following techniques:

Ray-Casting Techniques

In ray-casting, the arm remains at a constant length, and a virtual light ray extending from the hand is used to pick up and manipulate objects. When reeling is added, the object's distance from the user can be controlled by pressing joystick buttons, as in the indirect stretching technique.

The HOMER Techniques

After testing the above techniques, none proved completely satisfactory. Ray-Casting techniques made it easy to grab virtual objects, but manipulation was difficult. Arm-Extension techniques provided natural and efficient manipulation, but getting the hand in the correct position to grab objects was hard.

Therefore, we have created new techniques which combine the best features of the others to produce an easy-to-use, efficient technique for both grabbing and manipulating remote objects. These are called the HOMER (Hand-Centered Object Manipulation Extending Ray-Casting) Techniques.

Here, the user can grab an object using ray-casting, and manipulate it using natural hand motions. When an object is grabbed, the virtual hand immediately moves to the object and the object becomes attached to the hand. To move the object closer or farther away, either joystick buttons (Indirect HOMER) or a linear mapping of arm motion (Direct HOMER) may be used. These techniques are easy-to-use, extremely efficient, and provide complete control over objects' position and orientation.

NEW! Taxonomy of Selection and Manipulation Techniques

This taxonomy attempts to understand the range of possible techniques by first breaking down the task into subtasks using a task analysis method. The main subtask branches are selection, manipulation, and release. Possible techniques for subtasks are also listed. This taxonomy helps us to think systematically about the tasks involved and also to see how new techniques might be designed.

Large JPEG image of the taxonomy


  • Bowman, D. and Hodges, L., "An Evaluation of Techniques for Grabbing and Manipulating Remote Objects in Immersive Virtual Environments," in the Proceedings of the 1997 Symposium on Interactive 3D Graphics, 1997.
    Download as a Postscript file

  • Project Participant:

    Doug Bowman

    Contact Information:

    Doug A. Bowman - Graduate Student
    Georgia Institute of Technology
    College of Computing
    Atlanta GA 30332-0280
    (404) 894-5104 (Phone)

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