"Kenneth" <kdw### [at] earthlinknet> wrote in message 
news:web.43cc5cf4e3732dd0484f30@news.povray.org...
> I'm not sure, but the slope pattern may not be working correctly(?).
> I went back through the postings in several newsgroups, but didn't see
> anything about it.
>
> Using slope {0,-1,0} and without choosing Lo_slope and Hi_slope values, 
> the
> pattern does what is expected....covering the object "fully" with a
> color_map or texture from top to bottom (that is, assigning the color_map
> to the full 0-to-1 "slope"...all the object's normals.)
>
> But sticking in Lo_slope and Hi_slope values ...like 0, .5
> respectively...doesn't *seem* to do what the docs say:
>
> "By specifying Lo_slope and Hi_slope you get more control:
>  slope { <Direction>, Lo_slope, Hi_slope }
> Lo_slope and Hi_slope specifies which range of slopes are used, so you can
> control which slope values return which pattern values. Lo_slope is the
> slope value that returns 0.0 and Hi_slope is the slope value that returns
> 1.0."
>
> The way I read it, if I choose Lo_slope and Hi_slope to be 0 and .5, then
> the function should completely ignore any object normals outside that 
> range
> and should map the full color_map only to the specified normals, nowhere
> else. But the color map repeats at slope .5 and continues down to slope
> 1.0. ...in other words, it's re-applied to the object's
> normals that are outside the range.
> If I make Hi_slope something like .2, then the visual result is
> exactly the same as if I had used the frequency keyword on a typical
> pattern: the color map repeats five times.
>
> Is it meant to work this way? It would be much more useful (to me) if the
> colors were mapped ONLY to the object's specified normals range. For
> example, for "partially" texturing an object that already has another,
> earlier texture applied to it. Using <altitude> along with Lo-alt and 
> Hi_alt
> is a cumbersome way to go about that, with a somewhat different result 
> (and
> the color_map still repeats.)
>
> Ken Walker
>

You seem to be misinterpreting the way lo_slope and hi_slope work.  In the 
POV 3D world slopes between 0 and 1 are possible, with 0 being horizontal 
down, 0.5 being 90 deg vertical and 1 being horizontal up (relative to the 
direction vector).  The indexes in the slope map that the slope pattern uses 
will correspond to these (according to their waveform).  However, certain 
objects in POV like heightfields only have slopes from 0.5 to 1.0 with a 
direction vector of <0,1,0> (the docs use direction <0,-1,0> which makes it 
confusing if you don't catch that), so anything in the slope map outside 
that range is useles, so to give more control (read: finer control) the 
lo_slope and hi_slope can be redifined as 0.5 and 1.0, so that in the slope 
map, items with index 0.0 corespond to a slope of 0.5, and items with an 
index of 1.0 correspond to slopes of 1.0.  However, outside the hi and lo 
slope values, the pattern repeats as would any pattern type according to its 
waveform.  If, as I understand it, you want a texture only on the top half, 
you wouldn't use the hi_slope and lo_slope, instead, in the slope map, you 
would have no texture from index 0 to 0.5, and texture from 0.5 to 1.0.

hope this helps clear it up for you

-tgq

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