View source for LlGetSunDirection/ja

{{LSL_Function/ja
|func_id=177|func_sleep=0.0|func_energy=10.0
|func=llGetSunDirection|return_type=vector
|func_footnote=太陽の位置はSimオーナの希望次第で動的あるいは固定にできます。
|func_desc
|return_text=リージョンの太陽の方角
|spec
|caveats
|constants
|examples=これはスクリプトの動作により日中あるいは夜間（SL時間での短いもの）かどうかを素早く決定するのに用いることができます。返されるベクトルのZ要素が正の域の場合、太陽は地平線より上にあります。
<lsl>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 ]);
    }
}</lsl>
|helpers
|also_functions=
{{LSL DefineRow||[[llGetTimeOfDay/ja|llGetTimeOfDay]]|}}
|also_events
|also_tests
|also_articles
|notes=
<pre>AVERAGE_SUN_TILT = -.25 * pi
SEASONAL_SUN_TILT = .03 * pi
SUN_NORMALIZED_OFFSET = .45
</pre>
これはmSunOffsetがどのように計算されているかをあらわしています。
<cpp>F64 daily_phase  = DAILY_OMEGA * U64_to_F64(local_time / USEC_PER_SEC);
F32 sun_phase = (F32)fmod(daily_phase, 2.0*F_PI);
sun_hour -= 6.0f;
mSunOffset = HOURS_TO_RADIANS * sun_hour - (0.25f * F_PI) * cosf(HOURS_TO_RADIANS * sun_hour) - sun_phase;

//And here's how sun direction is calculated:

void LLRegion::calculateSunInfo(
       U64 current_time,
       LLVector3& directionp,
       LLVector3& ang_velocityp,
       F32& sun_phase)
{
   U64 local_time = current_time;
   if(getSunFixed())
   {
       local_time = 0;
   }
     // Sun moves (once a day) about a circle that lies on a tilted plane.
     // The angle of the plane cycles (once a year) a few radians about
     // some average.
     // These are F64's, otherwise we get rounding errors over time
   F64 daily_phase  = DAILY_OMEGA * U64_to_F64(local_time / USEC_PER_SEC) + mSunOffset;
   F64 yearly_phase = YEARLY_OMEGA * U64_to_F64(local_time / USEC_PER_SEC);
   F32 tilt = AVERAGE_SUN_TILT + SEASONAL_SUN_TILT_AMPLITUDE * (F32)sin(yearly_phase);

   sun_phase = (F32)fmod(daily_phase, 2.0*F_PI);
     // move sun around a circle
   directionp.setVec((F32)cos(-daily_phase), (F32)sin(-daily_phase), 0.0f);
     //tilt the circle about X-axis (due east)  
   directionp.rotVec(tilt, 1.0f, 0.0f, 0.0f);

     // calculate angular velocity (radians per second)
   ang_velocityp.setVec(0.0f, 0.0f, (F32)DAILY_OMEGA);
   ang_velocityp.rotVec((F32)tilt, 1.0f, 0.0f, 0.0f);

     // James wanted the night to be shorter than the day.
     // We can do this by offsetting the center of the sun's orbit in the positive
     // z-direction and normalizing the new vector.
   directionp.mV[VZ] += SUN_NORMALIZED_OFFSET;
   F32 R = directionp.normVec();

     // We also need to correct the angular velocity
     //
     // V = W % R
     // V has constant magnitude
     // As R goes up, W must go down
     // W and R are always perpendicular
     // ===>
     // W *= 1 / |R|
   ang_velocityp *= 1.0f / R;
}</cpp>
ソース：[https://lists.secondlife.com/pipermail/secondlifescripters/2007-July/001288.html Zyzzy Zarf]
|permission
|negative_index
|source
|sort=GetSunDirection
|cat1=Region
|cat2=Time
|cat3=Light
|cat4
|cat5
|cat6
}}