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"Russell Towle" <rto### [at] inreachcom> wrote:
> Hi,
>
> I believe there is an error in the documentation of sunpos.inc, at 3.7.20.6
> sunpos.inc.
>
> The example given reads
>
> //begin example
> #include "sunpos.inc"
>
> light_source {
> //Greenwich, noon on the longest day of 2000
> SunPos(2000, 6, 21, 12, 2, 0, 51.4667, 0.00)
> rgb 1
> }
>
> cylinder{
> <-2,0,0>,<2,0,0>,0.1
> rotate <0, Az-90, Al> //align cylinder with sun
> texture {...}
> }
> //end example
>
> However, if one experiments with changing the time of day, one will see that the
> cylinder does not align to the sun's direction. Changing to
>
> cylinder{
> <-2,0,0>,<2,0,0>,0.1
> rotate <0, 0, Al>
> rotate <0, Az-90, 0>
> }
>
> fixes the problem.
>
> It may help to use a plane at y=0 and a camera with y=up, a little above the
> plane, to see the cylinder's orientation.
I believe (untested) that changing it to this will also work:
cylinder{
<0,0,-2>,<0,0,2>,0.1
rotate <Al, Az-90, 0>
}
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