# Projector module question

Hi,
thanks for the updated “how to project on 3D geometry”-wiki, I wish I could have had the chance to be at the workshop!

I have a few questions related to the parameters of the projector module:

According to the wiki I should be able to calculate the lens shift based on info from the manual.
So far I have only done this by trial and error, but it would be great to understand the logic of this. It is probably very simple, but I suspect my brain isn´t wired up for this…

my sanyo manual has a chart similar to that in the wiki, so I know the height of the image at a certain distance, for instance at distance D=2400 the height H=1524. The perpendicular from the projector to the screen divides H into A and B, A:B=9:1.
So from this information I am able to calculate the different angles, but I don´t see how to turn this into something useful for the shift y parameter in the projector module?
By trial and error I have set the shift-Y value to .3844, but I am confused about what type of unit this refers to. First I thought it was a angle value, but that gives an angle of 138.38, which doesn´t make sense.

So, if someone could explain how I can turn the data from the manual into the magic shift-y value I would be very happy!

How do I determine the lens depth?
Do I just leave it at the default of -.0200?

The position of the projector is calculated from the center. Am I right in assuming that the module calculates the position of the cone based on the dimension of the projector?
Also, when measuring the position of the projector related to (0,0,0), should I always measure to the centre (both in depth and height) of the projector, or to the front (since the module already knows the dimension of the projector)?

thanks,
hc