From: owner-3dui@hitl.washington.edu on behalf of Jian Chen [jchen3@Bayou.UH.EDU] Sent: Thursday, September 27, 2001 4:03 AM To: Doug Bowman Cc: 3dui List Subject: RE: Comparison of HMD and Dome Dr. Bowman, I am sorry for my poor English. And thank you for your patience. On Wed, 26 Sep 2001, Doug Bowman wrote: > [Just a note to everyone; please remember to reply to the list, > not just to the person who sent the original message] > > Jian, > > I think this area (comparison of VE displays) is quite crucial. > It's obvious that not all VE displays are created equal, and it's > equally obvious that there is not one "best" display for all > VE applications. > > I think that's why Chad was asking about what types of tasks and > applications you would be focusing on. > > Let me just clarify what you're asking. I think you're asking > how to compare the two displays in a generic way so that you > can make a purchasing decision. Is that right? > Yes and no. We have both displays devices. The dome (at JSC-NASA) has been set up for about 5 years. It is a 3.7m diameter spherical dome. The inner surface is painted white and serves as a projection surface for two Triuniplex video projectors with custom wide angle optics (180x110 degree). The base rides on a 92 cm diameter bearing, and is gear driven to allow computer-controlled rotation of the trainee and the projectors about a vertical axis, with angular velocities up to 120degree/sec and accelerations up to 200 degree/sqr(sec). The trainee can be positioned (1) sitting upright, (2) lying on either the left or right side or (3) lying supine. It has different structure with those domes presented in your SIGGRAPH cource notes. We did buy a new Elumence projector due to the brightness and contrast problem with these two old projectors. I think what we are going to compare is a VR4 and the Elumence projector projected on our Dome screen. (I will post the Dome pictures on my webpage soon). The main task is for ground-based crew trainning applications at JSC, NASA. Currently, both VR4 and Dome are used, so they want to decide which one is better. > If so, then I think you have to try to generalize the tasks that > users will be performing, similar to my "testbed evaluation" (see > Presence 10(1)). The complex interaction tasks such as 3D selection > and manipulation are likely to show the widest differences between > the displays. Another way to approach the problem is to think about > what outcomes are most important for the users of your system. Is > it task performance time, comfort, level of presence, or something > else? > Generalizing the tasks performed in VE is exactly what I am doing. Your "testbed evaluation" paper is really useful. There is one point I got confused. I noticed that the model of the testbed (also other previous research) was created based on tasks. For instance, for selection and manipulation, a boxes scene was created; for travel , a town type scene was created. But in our model, we did all test by using only one model. The VE is a room with a set of 15 colored balls, cubes, torus, cylinders, and paramids (5 of each type, 3 of each color) along one wall and 15 matching platforms along the opposite wall. The task requires subjects to move the 15 balls on the left side the room over to the matching 15 platforms on the right side of the room. The subject has to go through a maze type walls, while avoiding the walls. We measure 6-DOF manipulation performance, task finishing time, sickness, and so on. Notice that subjects have to navigation to the object, pick up and then navigation, then drop. Two constant speeds are allowed. Does it matter we measure them together? My program did record all points (in each loop) subject traveled to. Should I seperate the task performace and discuss them? > Some fairly obvious observations: > -The dome requires the user to be seated. This might limit the amount > of natural head/body motion. The HMD can be used standing or seated. > > -The dome has a physical screen in space. This might be a problem in > certain 3D selection tasks if the virtual object is behind the screen > and the user is trying to reach for it. > > -The dome probably has a much wider field of view. > > -The HMD is more portable. > > -Setting orientation: the dome lends itself to a vehicle metaphor, where the > user stays stationary and rotates the world, while the HMD lends itself > to a natural/physical turning of the body to orient the viewpoint. > > Those are my initial thoughts. > Thank you so much. These are very good points. We tried to minimize the difference of the system setup. So we suppose that subject is sitting on a chair. I saw that the previous study by Pausch ( "a user study comparing head-mounted and stationary displays", IEEE Symposium on Research Frontier in Virtual Reality, 1993) has similar assumption. > --Doug > > -- > Doug A. Bowman, Ph.D. (540) 231-2058 > Assistant Professor (540) 231-6075 (fax) > Computer Science bowman@vt.edu > Virginia Tech www.cs.vt.edu/~bowman/ > > > thanks again, Jian ----------------------- University of Houston