Method for Calculating the longitude and latitude of a direct sun point

In a three-dimensional system, you must determine the sun position based on time and set this position as a specific light source.

To produce real lighting and shadow effects

 

The method for calculating the longitude and latitude of the direct sun point is as follows:

Based on the basic geographic knowledge,

Latitude: the latitude of a place with a height of 90 degrees

Longitude: the longitude of the place at noon.

 

The longitude is relatively good, 24 hours a day, the earth 360 degrees,

Longitude, time difference of 4 minutes

The longitude changes every minute, while the latitude changes every day.

 

Let's take a look at the longitude calculation method.

Export double callback calclongitude (double currlong, double currtime) <br/>{< br/> double res = 0.0; <br/> If (currlong> = 0) <br/> {<br/> res = (12.0-currtime) * 15.0 + currlong; <br/> If (RES> 180.0) <br/>{< br/> res-= 360.0; <br/>}< br/> else <br/> {<br/> res = currlong-(currtime-12.0) * 15.0; <br/> If (RES <-180.0) <br/> res + = 360.0; <br/>}< br/> return res; <br/>} 

 

Latitude calculation method, adapted from Python code on the Internet

The specific parameters are not understood, but the actual test is consistent with the actual situation.

Int calcday (INT year, int month, int day) <br/>{< br/> int leap = 0; <br/> If (Year % 4 = 0 & year % 100! = 0) | year % 400 = 0) <br/>{< br/> leap = 1; <br/>}< br/> else <br/> {<br/> leap = 0; <br/>}< br/> int mm [12] = {120, leap + 59, leap + 90, leap + 151, leap + 181, leap +, leap + 212, leap + 243, leap + 273, leap + 304, leap + 334}; <br/> return mm [month-1] + Day; <br/>}< br/> export double callback calclatitude (INT year, int month, int day) <br/>{< br/> Double tick = calcday (year, month, day)-79.6764-0.2422 * (year-1985) + int (year-1985)/4 ); <br/> double Sita = 2*3.14159265 * tick/365.2422; <br/> Double Delta = 0.3723 + 23.2567 * sin (SITA) <br/> + 0.1149 * sin (2 * SITA)-0.1712 * sin (3 * SITA) <br/>-0.758 * Cos (SITA) + 0.3656 * Cos (2 * SITA) <br/> + 0.0201 * Cos (3 * SITA); <br/> return delta; <br/>} 

 

Reference: http://blog.chinaunix.net/u/21370/showart_390554.html