"Warp" <war### [at] tagpovrayorg> schreef in bericht 
news:458072c4@news.povray.org...
> Thomas de Groot <t.d### [at] internldotnet> wrote:
>> >  Does trace() always return a normalized vector?
>
>> Yes, if you define also the fourth trace parameter (a vector), Norm in 
>> this
>> case (see documentation 3.2.1.4.5).
>
>  There's no such section number in the current documentation
> (http://povray.org/documentation/view/3.6.1/570/)
>
>  As for the documentation on the trace() function (2.2.1.4.5), it does not
> mention returning a normalized vector.
>

Strange....
My documentation for version 3.6 is headed:   3.2.1.4.5  Functions
This is what it says about trace():
quote
trace(OBJECT_IDENTIFIER, A, B, [VECTOR_IDENTIFIER]). trace helps you finding 
the exact location of a ray intersecting with an object's surface. It traces 
a ray beginning at the point A in the direction specified by the vector B. 
If the ray hits the specified object, this function returns the coordinate 
where the ray intersected the object. If not, it returns <0,0,0>. If a 
fourth parameter in the form of a vector identifier is provided, the normal 
of the object at the intersection point (not including any normal 
perturbations due to textures) is stored into that vector. If no 
intersection was found, the normal vector is reset to <0,0,0>.
Note: Checking the normal vector for <0,0,0> is the only reliable way to 
determine whether an intersection has actually occurred, intersections can 
and do occur anywhere, including at <0,0,0>.

unquote

so.... what do you think?

Thomas

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