"Tom Melly" <pov### [at] tomandlucouk> wrote:
> That latter I suspect. Re-read "3.3.1.2.2  Orthographic projection" and see
> if at least verifies that the orthographic camera is very confusing, even if
> it doesn't help you understand it (I never have).

I read it several times before posting. :-)

Actually, after sleeping on it for a while I figured out what the problem
wsa.

> That said, specifying a "look_at" point might help....

You're right. The problem was that because I was translating the camera, the
look_at point was always <0,0,1> away from the camera position. Since the
camera effectively creates its "window" at the look_at point, this means
that once I moved more than a certain distance, the spheres were behind the
"window."

In short, with a perspective camera, you can see anything in front of the
camera. With an orthographic camera, you can only see things beyond the
look_at point. Except that you seem to be able to see a whole object if any
part of it is beyond the look_at point. (That's why I had the camera so
close in the first place - part of a height_map was obscuring the shot I
wanted.)

Since the distance between the camera location and the look_at point makes
no difference to the view you get with an orthographic camera, the trick is
just to move the look_at point really close to the camera to make sure that
everything is past it.

Thanks for the reply!

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