[PD] GEM position parameters

Mathieu Bouchard matju at artengine.ca
Tue Feb 14 13:41:32 CET 2006


On Tue, 14 Feb 2006, Michael Mihocic wrote:

> What units do the point parameters, e.g. first three parameters of view
> (<view_x> <view_y> <view_z>) have? I am asking because I want to use a
> head mounted display and I want to present a steroe figure in a defined
> distance.

Whatever the units are in the 3-D space, they cancel out with the
flattening: meters/meter, cubits/cubit, inches/inch, all those are
non-units. This is because a point in 3-D space (x,y,z) becomes
(k*x/z,k*y/z). The constant "k" can be imagined to be in whichever units
you want, but in GEM it tends to be some fraction of the window's size in
pixels.

PS: The formula I just gave assumes the simplest point of view of being at 
the origin looking at a screen that cuts the positive z axis at a right 
angle. There are other points of view but the units still cancel out.

 _ _ __ ___ _____ ________ _____________ _____________________ ...
| Mathieu Bouchard - tél:+1.514.383.3801 - http://artengine.ca/matju
| Freelance Digital Arts Engineer, Montréal QC Canada




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