Dre <and### [at] gmailcom> wrote:
> "Warp" <war### [at] tagpovrayorg> wrote in message 
> news:4bbda1be@news.povray.org...
> > Dre <and### [at] gmailcom> wrote:
> >> Yet this does:
> >
> >> #declare norm = <0, 0, 0>;
> >> #declare startPoint =<xPos, 10, zPos>;
> >> #declare endPoint = <xPos, -10, zPos>;
> >> trace(object, startPoint, endPoint, norm)
> >
> >  I don't think it does (well, not in the way you want). The third 
> > parameter
> > of trace() specifies a direction, not an endpoint.
> >
> >  Probably you want the third parameter to be <0, -1, 0> because that's
> > the direction you are shooting the rays towards.
> >
> > -- 
> >                                                          - Warp

> Well it does to what I want now that I changed the way I coded it to the 
> example above.  I then modified the norm as you stated but it didn't make 
> any difference at all.  Both my norm and yours are below my start point so 
> they are essentially shooting the rays in the same direction.

  The normal is the *fourth* parameter. I was talking about the *third*
parameter, which is the direction. That should be <0, -1, 0>.

-- 
                                                          - Warp

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