LightWorld Class

// creating a world light source and setting its color to white (1.0f, 1.0f, 1.0f, 1.0f)
LightWorld thesun = new LightWorld(vec4(1.0f, 1.0f, 1.0f, 1.0f));

// setting the name of the world light
thesun.setName("Sun");
	
// setting disable angle of the world light
thesun.setDisableAngle(90.0f);

// setting light intensity
thesun.setIntensity(1.0f);
	
// setting scattering type to sun scattering
thesun.setScattering(LIGHT_WORLD_SCATTERING_SUN);

/// function calculating azimuth and elevation for the specified date, time (GMT) and geo-coordinates (https://stackoverflow.com/questions/8708048/position-of-the-sun-given-time-of-day-latitude-and-longitude)
void sunPosition(double & elevation, double & azimuth, double lat, double lon, int year=2019, int month=12, int day=31, double hour=23, int min=59,int sec=59) {
    double pi = 3.141592650f;
    double twopi = 2 * pi;
    double deg2rad = pi / 180.0f;

    // get a day of the year, e.g. Feb 1 = 32, Mar 1 = 61 on leap years
    int month_days[13] = ( 0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30 );
    for (int i=0; i<month; i++)
        day += month_days[i];
    int leapdays = (year % 4) == 0 && ((year % 400) == 0 || (year % 100) != 0) && day >= 60 && !(month==2 && day==60);
	if (leapdays > 0) day++;
	
    // Get Julian date - 2400000
    hour += min / 60.0f + sec / 3600.0f; // hour plus fraction
    double delta = year - 1949.0f;
    double leap = int(delta / 4.0f); // former leapyears
    double jd = 32916.5f + delta * 365 + leap + day + hour / 24.0f;

    // calculating input for the Astronomer's almanach as the difference between
    // the Julian date and JD 2451545.0 (noon, 1 January 2000)
    double time = jd - 51545.0f;

    // calculating mean longitude and mean anomaly
	double mnlong = 280.460f + 0.9856474f * time;
    mnlong = mnlong % 360;
    if (mnlong < 0) mnlong += 360;
    double mnanom = 357.528f + 0.9856003f * time;
    mnanom = mnanom %360;
    if (mnanom < 0) mnanom += 360;
    mnanom *= deg2rad;

    // calculating ecliptic longitude and obliquity of ecliptic
    double eclong = mnlong + 1.915f * sin(mnanom) + 0.020f * sin(2 * mnanom);
    eclong = eclong % 360;
    if (eclong < 0) eclong+= 360;
    double oblqec = 23.439f - 0.0000004f * time;
    eclong *= deg2rad;
    oblqec *= deg2rad;

    // calculating celestial coordinates: right ascension and declination
    double num = cos(oblqec) * sin(eclong);
    double den = cos(eclong);
    double ra = atan(num / den);
    if (den < 0) ra += pi;
    if (den >= 0 && num < 0) ra += twopi;
    double dec = asin(sin(oblqec) * sin(eclong));

    // calculating local coordinates Greenwich mean sidereal time
    double gmst = 6.697375f + 0.0657098242f * time + hour;
    gmst = gmst % 24;
    if (gmst < 0) gmst+= 24.0f;

    // calculating local mean sidereal time
    double lmst = gmst + lon / 15.0f;
    lmst = lmst %24;
    if (lmst < 0) lmst += 24.0f;
    lmst = lmst * 15.0f * deg2rad;

    // calculating hour angle
    double ha = lmst - ra;
    if (ha < -pi) ha += twopi;
    if (ha > pi) ha -= twopi;

    // converting latitude to radians
    lat = lat * deg2rad;

    // calculating azimuth and elevation
    elevation = asin(sin(dec) * sin(lat) + cos(dec) * cos(lat) * cos(ha));
    azimuth = asin(-cos(dec) * sin(ha) / cos(elevation));

    // for logic and names, see Spencer, J.W. 1989. Solar Energy. 42(4):353
    int cosAzPos = (0 <= sin(dec) - sin(elevation) * sin(lat));
    int sinAzNeg = (sin(azimuth) < 0);
    if (cosAzPos && sinAzNeg) azimuth +=twopi;
    if (!cosAzPos) azimuth=  pi - azimuth;

    // return elevation and azimuth
    elevation = elevation / deg2rad;
    azimuth = azimuth / deg2rad;
}

int init() {
	/* ... */
	
	// geo-coordinates of a point (latitude and longitude)
	double lat = 56.49771;
	double lon = 84.97437;

	// elevation and azimuth to store calculated values
	double elevation, azimuth;
	
	// getting the default world light source named "sun"
	LightWorld sun = node_cast(engine.world.getNodeByName("sun"));
	if (sun!=NULL) {
		// calculating azimuth and elevation
		// for the specified date,
		// GMT time and geo-coordinates
		sunPosition(elevation,azimuth, lat, lon, 
					2019, 2, 5, 				// February 5, 2019
					4, 0, 0);					// 04:00:00 (GMT)
		
		// setting real Sun position for the calculated azimuth and elevation values 
		sun.setRotation( quat(90,270,270) * quat(azimuth,0,0) * quat(0,90,0) * quat(elevation,0,0) * quat(90,0,0) );
	}

	return 1;
}

LightWorld Class

Members

---

static LightWorld ( vec4 color ) #

Constructor. Creates a new world light source with a given color.

Arguments

• vec4 color - Color of the new light source.

void setMode ( int mode ) #

Sets rendering mode for the light source. This option determines whether the light is to be rendered as a dynamic or static one.

Arguments

• int mode - Light mode, one of the LIGHT_MODE_* variables.

int getMode ( ) #

Returns the current rendering mode for the light source. This option determines whether the light is to be rendered as a dynamic or static one.

Return value

Light mode, one of the LIGHT_MODE_* variables.

void setDisableAngle ( float angle ) #

Sets an angle at which the light source is disabled (shadows and the diffuse component is disabled). However, the light source still affects scattering.

Arguments

• float angle - Angle at which the light source is disabled.

float getDisableAngle ( ) #

Returns an angle at which the light source is disabled (shadows and the diffuse component is disabled). However, the light source still affects scattering.

Return value

Angle at at which the light source is disabled.

void setNumShadowCascades ( int cascades ) #

Sets the number of shadow cascades with different shadow maps. All the shadow maps have the same resolution, but are applied to different cascades. Thus, close-range shadows are of higher quality and distant ones of lower.

Arguments

• int cascades - Number of shadow cascades. Accepted values are from 1 to 4. The default is 4.

int getNumShadowCascades ( ) #

Returns the number of shadow cascades with different shadow maps. All the shadow maps have the same resolution, but are applied to different cascades. Thus, close-range shadows are of higher quality and distant ones of lower.

Return value

The number of shadow cascades. The minimum number of cascades is 1, the maximum is 4.

void setScattering ( int scattering ) #

Sets a lighting type for the world light.

Arguments

• int scattering - One of the LIGHT_WORLD_SCATTERING_* variables.

int getScattering ( ) #

Returns a lighting type set for the world light.

Return value

One of the LIGHT_WORLD_SCATTERING_* variables.

void setShadowCascadeMode ( int mode ) #

Sets the shadow cascade generation mode for the world light source. There are two modes available:

• Dynamic - shadow cascades are built dynamically relative to the camera's position.
• Static - shadow cascades are built relative to the world light's position and baked. This mode is suitable for archviz projects.

Arguments

• int mode - Shadow cascade mode, one of the LIGHT_SHADOW_CASCADE_MODE_* variables.

int getShadowCascadeMode ( ) #

Returns the current shadow cascade generation mode for the world light source. There are two modes available:

• Dynamic - shadow cascades are built dynamically relative to the camera's position.
• Static - shadow cascades are built relative to the world light's position and baked. This mode is suitable for archviz projects.

Return value

Shadow cascade mode, one of the LIGHT_SHADOW_CASCADE_MODE_* variables.

void setShadowCascadeBorder ( int num, float r ) #

Sets the multiplier for the distance to the border of the specified shadow cascade at which the corresponding shadows are rendered.

Arguments

• int num - Number of the cascade in range [0;num_cascades-1].
• float r - Distance multiplier to be set, in range [0; 1].

float getShadowCascadeBorder ( int num ) #

Returns the multiplier for the distance to the border of the specified shadow cascade at which the corresponding shadows are rendered.

Arguments

• int num - Number of the cascade in range [0;num_cascades-1].

Return value

Current distance multiplier, in range [0;1].

void setShadowHeight ( float height ) #

Sets the view height of the orthographic projection used for generation of static shadow cascades. Static cascades are generated relative to the world light's position.

Arguments

• float height - View height of the orthographic projection used for shadow cascade generation, in units.

float getShadowHeight ( ) #

Returns the current view height of the orthographic projection used for generation of static shadow cascades. Static cascades are generated relative to the world light's position.

Return value

Current view height of the orthographic projection used for shadow cascade generation, in units.

void setShadowWidth ( float width ) #

Sets the view width of the orthographic projection used for generation of static shadow cascades. Static cascades are generated relative to the world light's position.

Arguments

• float width - View width of the orthographic projection used for shadow cascade generation, in units.

float getShadowWidth ( ) #

Returns the current view width of the orthographic projection used for generation of static shadow cascades. Static cascades are generated relative to the world light's position.

Return value

Current view width of the orthographic projection used for shadow cascade generation, in units.

void setShadowZFar ( float zfar ) #

Sets the distance to the far clipping plane to be used for generation of static shadow cascades. Static cascades are generated relative to the world light's position.

Arguments

• float zfar - Distance to the far clipping plane to be used, in units.

float getShadowZFar ( ) #

Returns the current distance to the far clipping plane used for generation of static shadow cascades. Static cascades are generated relative to the world light's position.

Return value

Distance to the far clipping plane currently used, in units.

static int type ( ) #

Returns the type of the node.

Return value

Light type identifier.

vec2 getRenderShadowDepthRange ( ) #

Returns shadow depth range for the light source.

Return value

Shadow depth range for the light source as a two-component vector (min, max).

Mat4 getRenderShadowCascadeModelview ( int num ) #

Returns the model-view matrix for the specified shadow cascade.

Arguments

• int num - Shadow cascade number in the [0;num_cascades-1] range.

Return value

Shadow cascade model-view matrix matrix.

mat4 getRenderShadowCascadeProjection ( int num ) #

Returns the shadow cascade projection matrix for the specified cascade number.

Arguments

• int num - Shadow cascade number in the [0;num_cascades-1] range.

Return value

Shadow cascade projection matrix.

void updateRenderShadowCascadeMatrices ( Vec3 camera_position, float zfar ) #

Updates projection matrices for the shadow cascades of the light source in accordance with the specified camera position and distance to the far clipping plane.

Arguments

• Vec3 camera_position - Position of the camera in world coordinates.
• float zfar - Distance to the far z-clipping plane, in units.