Hi,

I've post my problem in here long time ago. But my problem haven't 
solved yet. Here is the revision of my problem.

I'm doing position tracking with some marker base system (using computer 
vision technique). This system is finished and I'm going to use it as a 
base of an application which I'm going to develop. (It is about 
augmented reality)

What I've done so far is the simulation tracking and the real world 
tracking. The result of real world tracking is very accurate, with about 
+/-3cm deviation. But for the simulation, though the planar position (x 
and y) is very accurate, but the distance (z) is very inaccurate, with 
the average deviation of about 40cm. Which is very unacceptable.

For now, I'm going to vary the focal length of the camera to see if it 
is related, but seems it is not the source of error. I've read from this 
newsgroup that the pov-ray unit is not related to the real world unit 
(centimeter or meter). Would it be the source of the error?

And also, reply from the previous post suggest that I've distorded the 
output image. I've double check it and I'm not distorting it.

So anyone has any clue on it?

Here is my camera definition, which is simulating the real camera in the 
real world tracking:

camera
{
    location <61.5, 74.55, -200>
    direction <0, 0, 1.7526>
    look_at <61.5, 74.55, 0>
}

As this is a square pixel camera, and with normal 4/3 aspect ratio, so 
the image is rendered with the dimension 384x288 (both resolution are 
the same).

P.S.: markers are texture mapped into the virtual scene.


cheers
Colin

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