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Old 08-24-2009, 12:45 PM
Arandia Arandia is offline
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Join Date: Aug 2009
Posts: 2
Head tracking, Flock of Birds and vizcave; how do I connect them?

Hello,

I've been struggling with this problem for a while now. I have an Ascension Flock of Birds (FoB), which I am using to collect the position of the user's head when they're wearing it. I've got it up and running inside Vizard; on that, no problems.

My problem is related to how to use the FoB data to create an illusion of 3D space via headtracking - somewhat similar to what Johnny Lee did here (Youtube link).

I've tried using the vizcave module to interpret this data, so as to avoid having to shift object positions manually, etc, etc. My first problem appears to be that I am initializing the cave wall wrong - I have captured the positions in FoB space of the corners of my monitor, and fed them into vizcave.Wall().
Code:
self.__cave = vizcave.Cave()
wall = vizcave.Wall(upperLeft  = (-.1585, .3409, .1739+.05),
                    upperRight = ( .1959, .3339, .1852+.05),
                    lowerLeft  = (-.2029, .0795, .1459+.05),
                    lowerRight = ( .2169, .0782, .1593+.05))
self.__cave.addWall(wall)
The '+.05' is because I measured to 5 cm away from my screen, to avoid magnetic irregularities. However, when I run this by itself, I get a slanted view out. However, it seems to me that it should start out looking straight ahead - I've done nothing else to rotate or change the field of view. I've corrected the FoB coordinate system to match with Vizard, but I'm guessing the little differences in the measurements were enough to torque the view? Is there any way around this, or am I feeding vizcave.Wall() all the wrong data?


I have a function that is registered to be called on every viz.UPDATE_EVENT, that eventually runs "self.__cave.update(pos=aPos)", where aPos is a vector specifying how far the user's head has moved since the simulation began. This gives me my second problem - while moving the FoB sensor left and right causes my display to sway left and right, it doesn't do it appropriately for a 3D illusion. In other words, what I'm trying to achieve is to have the display look as though it is a window into the vizard world, so that as you move your head left and right elements on the screen shift appropriately, with ones farther from the screen shifting more. Vizcave seems to just shift all elements uniformly, regardless of their position. Is it even supposed to do what I'm looking for, or am I simply doing something wrong? Again, I'm pretty sure I've already accounted for the differing coordinate systems, so I don't think it's the data I'm feeding it.

My last (and probably biggest) problem is that the ultimate goal of my project is to get this headtracking simulation running on an Elumens curved display dish. I can get the display to be correctly distorted with the 'spi' module, but rather unfortunately I found that running the spi and vizcave modules simultaneously seems to cause the vizcave module to stop working completely. I'm using the latest version of Vizard (3.14.0004). Is there any way around this problem, or am I really wasting my time with the vizcave module? The only other solution to this problem I can see involves manually modifying the positions of all the world elements every frame update, but this would certainly be a slow and labourious process. Is there any other way to screw with the display frustum?

Thanks for any help on these matters.
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