Hi,
If you want to offset the viewpoint from the tracker, then you cannot use automatic head tracking with Vizard 2.5. If you are willing to use Vizard 3.0, it comes with built-in features to do just this. With 2.5 you will have to manually compute the tracker matrix and apply the LED/Camera offset yourself. The code would be something like this:
Code:
m = computeTrackerTransform() #You must implement this
LED_CAMERA_OFFSET = [0,-0.01,0.01] #Position offset of camera relative to LED
m.preTrans(LED_CAMERA_OFFSET)
print m.getTrans() #Camera position