LlGetSunDirection

De DigiWiki.

Phase	PST	PDT	GMT
Sunset	2:30 AM	3:30 AM	10:30
Midnight	3:00 AM	4:00 AM	11:00
Sunrise	3:30 AM	4:30 AM	11:30
Sunset	6:30 AM	7:30 AM	14:30
Midnight	7:00 AM	8:00 AM	15:00
Sunrise	7:30 AM	8:30 AM	15:30
Sunset	10:30 AM	11:30 AM	18:30
Midnight	11:00 AM	12:00 PM	19:00
Sunrise	11:30 AM	12:30 PM	19:30
Sunset	2:30 PM	3:30 PM	22:30
Midnight	3:00 PM	4:00 PM	23:00
Sunrise	3:30 PM	4:30 PM	23:30
Sunset	6:30 PM	7:30 PM	2:30
Midnight	7:00 PM	8:00 PM	3:00
Sunrise	7:30 PM	8:30 PM	3:30
Sunset	10:30 PM	11:30 PM	6:30
Midnight	11:00 PM	12:00 AM	7:00
Sunrise	11:30 PM	12:30 AM	7:30

One possible application for this function is to determine whether it's day- or nighttime. The following script simply uses the z-axis of the sun's vector to find out if the sun is above or below the horizon:

integer night=0; // 0 = daytime, 1 = nighttime
 
default
{
    state_entry()
    {
        llSetTimerEvent(300); // Check every 5 minutes
    }
    timer()
    {
        vector sun = llGetSunDirection();
        if (sun.z <= 0) night = 1; // Sun is below the horizon
        else if (sun.z > 0) night = 0; // Sun is above the horizon
    }
    touch_start(integer total_number)
    {
        if (night == 1) llSay(0, "It's nighttime.");
        else if (night == 0) llSay(0, "It's daytime.");
    }
}

If the complete script is to behave different at night, an additional script state may be a better solution than checking a variable:

default // daytime state
{
    state_entry()
    {
        llSetTimerEvent(180); // Check every 3 minutes
    }
    timer() 
    { 
        vector sun = llGetSunDirection(); 
        if (sun.z < 0) state night; 
    }
    touch_start(integer total_number)
    {
        llSay(0, "It's daytime.");
    }    
}
 
state night
{ 
    state_entry() 
    { 
        llSetTimerEvent(180); // Check every 3 minutes
    } 
    timer() 
    { 
        vector sun = llGetSunDirection(); 
        if (sun.z > 0) state default; // Change back to daytime state
    } 
    touch_start(integer total_number)
    {
        llSay(0, "It's nighttime.");
    }
}

Rotating the object to follow the path of the sun during day time and return to a default position at night:

vector sun;
 
default
{
    state_entry()
    {
        llSetTimerEvent(300); // Check every 5 minutes
    }
    timer()
    {
        vector sun = llGetSunDirection();
 
        if (sun.z <= 0) { // If it is night, return to default position
            llSetRot( <0, 0, 0, 0> );
        } else if (sun.z > 0) {
            rotation sunRot = ZERO_ROTATION; // Set the rotation to NULL 
 
            if (sun.z >= 0.0) { // If it is day, set rotation towards the sun
                sunRot = llAxes2Rot(<sun.x, sun.y, 0.0>, <-sun.y, sun.x, 0.0>, <0.0, 0.0, 1.0>);
            }
            llSetRot(sunRot);
        }        
    }
}

This can be used to quickly determine whether it is day or night (in shortened SL days) as the script runs: if the returned vector's Z element is positive, then the sun is above the horizon.

integer lightsOn = -1;//not TRUE or FALSE
 
CheckSun()
{
    vector sun = llGetSunDirection();
    integer turnLightsOn = (sun.z < 0);
    if(turnLightsOn != lightsOn)
    {
        lightsOn = turnLightsOn;
        llSetPrimitiveParams([ PRIM_FULLBRIGHT, ALL_SIDES, lightsOn ]);
    }
}