sunpos.inc

### 7.21.6 sunpos.inc

This file only contains the sunpos() macro

`sunpos(Year, Month, Day, Hour, Minute, Lstm, LAT, LONG)`. The macro returns the position of the sun, for a given date, time, and location on earth. The suns position is also globally declared as the vector `SolarPosition`. Two other declared vectors are the `Az` (Azimuth) and `Al` (Altitude), these can be usefull for aligning an object (media container) with the sunlight.
Assumption: in the scene north is in the +Z direction, south is -Z.
Parameters:

- `Year`= The year in four digits.
- `Month`= The month number (1-12).
- `Day`= The day number (1-31).
- `Hour`= The hour of day in 24 hour format (0-23).
- `Minute`= The minutes (0-59).
- `Lstm`= Meridian of your local timezone in degrees (+1 hour = +15 deg, east = positive, west = negative)
- `LAT`= Lattitude in degrees.decimal, northern hemisphere = positive, southern = negative
- `LONG`= Longitude in degrees.decimal, east = positive, west is negative

Use :

       #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 {...}
       }