ingo <ing### [at] tagpovrayorg> wrote:

> from a stereo cam:
> #local D2_X_Fn = function(u,v){
>   select(
>     (u<=0),   //u<0????
>     -1,
>     D1R_X_Fn((u/AspectU*image_width)-0.25,v),
>     D1L_X_Fn((u/AspectU*image_width)+0.25,v)
>   )
> };
>
> the alternative is select only smaller or bigger resulting in a pixel wide
> black line.
>
> So, what to do with the pixel in the middle? Another select with u=0?




Well, that's a pretty interestingly constructed select() function.

I would have done away with the Boolean operator and the semicolon.
I don't think the one you're using ever results in a <0 value for select() to
operate on, since the boolean operator only returns 0 or 1.
So just to keep myself sane during debugging, I'd write it like:

#local D2_X_Fn = function(u,v){
     select (u,
          D1L_X_Fn ((u/AspectU*image_width)+0.25,v))  // u <  0
          D1R_X_Fn ((u/AspectU*image_width)-0.25,v))  // u >= 0
     )
}

I guess if you wanted that one-pixel wide strip at the center to use the other
function, then you'd use the 4-argument version and repeat the first function
for the u = 0 case.



Hopefully at some point you can share some of your understanding of the
user-defined camera with a few simple explanatory examples / tutorials.

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