In article <1flp1lf.b3ye8bmkt22oN%kaveh@delete_this.focalimage.com>,
 kav### [at] delete_thisfocalimagecom (Kaveh) wrote:

> Is this really the reason? So has everyone else got it wrong, e.g.
> maths, physics, etc?

In screen coordinates, x is usually from left to right, and y from 
bottom to top. The left handed coordinate system is simply an extension 
of this: z going into the screen. It is not something unique to POV, it 
is used in many other places as well.
Even in right handed coordinate systems, the y axis is often "up" 
(OpenGL for example). The difference is that the z axis points out of 
the monitor instead of into it. A depth buffer is often called a 
"z-buffer", but never a "y-buffer". I think the main source of the "z is 
up" system is actually architectural drawings, it makes sense when x and 
y are already used for a horizontal plane on paper. In math, I often see 
the z coordinate visualized as depth into a graph instead of height.

Neither way is "wrong", they are just different conventions. An analogy 
would be row-major vs. column-major matrices.

-- 
Christopher James Huff <cja### [at] earthlinknet>
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG: chr### [at] tagpovrayorg
http://tag.povray.org/

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