Am 18.08.2013 22:39, schrieb Alain:

>  From the documentations:
> "The look_at vector tells POV-Ray to pan and tilt the camera until it is
> looking at the specified x, y, z coordinates."
>
> Whenever the y position of the camera and look_at are different, the
> camera will tilt up or down,
> Depending on the x and z coordinates, and the order of the pan and tilt,
> it can look as if the camera did rotate around the z axis as well as the
> x axis.
>
> This can cause unexpected result if it cause the camera to look straight
> up or down.
> When looking straight up or down, you need to provide the up vector.
> Another way is to create the camera at the origin, looking toward +z
> (the default), and use rotate -90*x to look up and rotate 90*x to look
> down.

You know what? This sucks. The issue of trying to figure out the camera 
parameters crops up so frequently that I think it really needs to be 
addressed in the form of an inbuilt feature at the next possible 
opportunity.

I'm thinking along the lines of (1) a function (or set of functions) to 
retrieve the effective up, right and direction vectors, and (2) a 
function (or pair of functions) to return the effective camera position 
and direction vector corresponding to any given position in the output 
image (x,y ranging from 0.0 to 1.0 each). Also nice to have would be (3) 
a function to retrieve the effective camera angle (if applicable for the 
selected camera).

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