In article <3a604230@news.povray.org>, "Marc-Hendrik Bremer" 
<Mar### [at] t-onlinede> wrote:

> I want to texture the part of an object that is  under an "overhang"
> differently from the rest. I.e. I would like to use a slope y (or was
> it -y?) and when it is negative, I want to give the part in -y-direction a
> different pigment even if the slope is positive again.

I'm not sure what you mean..."when it is negative...", "...even if the 
slope is positive again."
The slope is either negative or positive (actually, it goes from 0 to 
1). Do you want a texture that covers the downward facing area as well 
as part of the upward-facing area? That should be easy to do simply by 
making your blend map partially solid. For example:
slope y
*_map {
    [0 Bottom]
    [0.5 Bottom]
    [0.6 Top]
    [1 Top]
}

Just remember that slope varies "between (and including) 0.0 and 1.0, 
where 0.0 is most negative slope (surface normal points in negative 
vector direction), 0.5 corresponds to a vertical slope (surface normal 
and slope vector form 90 degree angle) and 1.0 is horizontal with 
respect to the slope vector (surface normal parallel to slope vector)".

-- 
Christopher James Huff
Personal: chr### [at] maccom, http://homepage.mac.com/chrishuff/
TAG: chr### [at] tagpovrayorg, http://tag.povray.org/

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