Using <window>.screenToWorld within vizcave powerwall

[VizMars]

How can one use the <window>.screenToWorld command within a vizcave powerwall?
Specifically, how can one get the length of the line passing through the given screen coordinates (in pixel units) with the begin point of the line being the users head position (center of the eyes)?

Unfortunately, the following code seems to be incorrect:

line = viz.MainWindow.screenToWorld([pixel_x,pixel_y], eye = viz.BOTH_EYE, mode = viz.WINDOW_PIXELS)
print line.length

[Jeff]

Is the line length you want to calculate the distance from the user's head to a specific point on the physical wall?

[VizMars]

I want to calculate depth information for each screen pixel in a way that for given 2d screen coordinates (x,y) I get the distance from the user's head to the point in the 3d scene that corresponds to the given 2d screen coordinates. Ultimately, the goal is to construct a "depth map" for a scene given the user's head position and gaze direction.

[Rennschu]

I would like to use this function, too. Is it possible to create a depth map in Vizard this way?

[Jeff]

You can render the scene to a depth map or use viz.window.screenCapture with a depth texture to capture the current scene depth info.

[VizMars]

Thank you for providing this link. Afaiu d and z (in the example you linked) are two variables that hold standardized depth values, and z is used to construct the color for the depth texture.
I have a two questions regarding this example:
1. Can you explain what exactly d and z correspond to? And if they are standardized, is it also possible to get the unstandardized distance/depth information?
2. How can I get these values (d and z) for each pixel?
viz.window.screenCapture() allows me to save the screen image to a file where I can extract the r, g and b values from (not sure how they correspond to d and z) - but I think it would be better to get the depth information within Vizard. Is this possible?