Unigine::LightWorld Class

Example#

The following code illustrates how to create a world light source and set its parameters (intensity scattering, etc.).

Source code (C++)

#include <UnigineLights.h>

using namespace Unigine;

	/* .. */

// creating a world light source and setting its color to white (1.0f, 1.0f, 1.0f, 1.0f)
	LightWorldPtr thesun = LightWorld::create(Math::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(LightWorld::SCATTERING_SUN);

Setting Position#

A world light is an infinitely distant light source, so its physical position is not important, only the direction matters, as it defines orientation of shadows. You can change the light's direction via the setRotation() method.

Let's illustrate that by setting the correct position of the Sun for a certain geographic location (latitude, longitude), date and time. To calculate elevation and azimuth values let's use the following sunPosition() function:

sunPosition() function:

Source code (C++)

#include <UnigineWorld.h>

using namespace Unigine;

/// 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 = 2012, int month = 12, int day = 22, double hour = 12, int min = 00, int sec = 00) {
	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 Atronomer'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 = remainder(mnlong, 360);
	if (mnlong < 0) mnlong += 360;
	double mnanom = 357.528f + 0.9856003f * time;
	mnanom = remainder(mnanom, 360);
	if (mnanom < 0) mnanom += 360;
	mnanom *= deg2rad;

	// calculating ecliptic longitude and obliquity of ecliptic
	double eclong = mnlong + 1.915f * Math::sin(mnanom) + 0.020f * Math::sin(2 * mnanom);
	eclong = remainder(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 = Math::cos(oblqec) * Math::sin(eclong);
	double den = Math::cos(eclong);
	double ra = Math::atan(num / den);
	if (den < 0) ra += pi;
	if (den >= 0 && num < 0) ra += twopi;
	double dec = Math::asin(Math::sin(oblqec) * Math::sin(eclong));

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

	// calculating local mean sidereal time
	double lmst = gmst + lon / 15.0f;
	lmst = remainder(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 = Math::asin(Math::sin(dec) * Math::sin(lat) + Math::cos(dec) * Math::cos(lat) * Math::cos(ha));
	azimuth = Math::asin(-Math::cos(dec) * Math::sin(ha) / Math::cos(elevation));

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

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

Thus, we can simply set the position of the Sun as follows:

Source code (C++)

#include <UnigineWorld.h>

int AppWorldLogic::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"
	LightWorldPtr sun = checked_ptr_cast<LightWorld>(World::getNodeByName("sun"));
	if (sun)
	{
		// 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(Math::quat(90, 270, 270) * Math::quat((float)azimuth, 0, 0) * Math::quat(0, 90, 0) * Math::quat((float)elevation, 0, 0) * Math::quat(90, 0, 0));
	}

	return 1;
}

Methods:

Name	Description View: Sort by:
*create*	Constructor.
setMode	Sets rendering mode for the light source.
getMode	Returns the current rendering mode for the light source.
setDisableAngle	Sets an angle at which the light source is disabled (shadows and the diffuse component is disabled).
getDisableAngle	Returns an angle at which the light source is disabled (shadows and the diffuse component is disabled).
setNumShadowCascades	Sets the number of shadow cascades with different shadow maps.
getNumShadowCascades	Returns the number of shadow cascades with different shadow maps.
setScattering	Sets a lighting type for the world light.
getScattering	Returns a lighting type set for the world light.
setShadowCascadeMode	Sets the shadow cascade generation mode for the world light source.
getShadowCascadeMode	Returns the current shadow cascade generation mode for the world light source.
setShadowHeight	Sets the view height of the orthographic projection used for generation of static shadow cascades.
getShadowHeight	Returns the current view height of the orthographic projection used for generation of static shadow cascades.
setShadowWidth	Sets the view width of the orthographic projection used for generation of static shadow cascades.
getShadowWidth	Returns the current view width of the orthographic projection used for generation of static shadow cascades.
setShadowZFar	Sets the distance to the far clipping plane to be used for generation of static shadow cascades.
getShadowZFar	Returns the current distance to the far clipping plane used for generation of static shadow cascades.
getRenderShadowDepthRange	Returns shadow depth range for the light source.
setOneCascadePerFrame	Sets the value indicating if the One Cascade Per Frame mode is enabled.
isOneCascadePerFrame	Returns the value indicating if the One Cascade Per Frame mode is enabled.
setShadowCascadeBorder	Sets the multiplier for the distance to the border of the specified shadow cascade at which the corresponding shadows are rendered.
getShadowCascadeBorder	Returns the multiplier for the distance to the border of the specified shadow cascade at which the corresponding shadows are rendered.
type	Returns the type of the node.
getRenderShadowCascadeModelview	Returns the model-view matrix for the specified shadow cascade.
getRenderShadowCascadeProjection	Returns the shadow cascade projection matrix for the specified cascade number.
updateRenderShadowCascadeMatrices	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.

LightWorld Class

Enums

SCATTERING#

Name	Description
SCATTERING_NONE = 0	Render the atmosphere with no influence of the global lights (sun and moon), i.e. the light gradient won't be changed in any direction.
SCATTERING_SUN = 1	Render the atmosphere in accordance with the Sun's lighting.
SCATTERING_MOON = 2	Render the atmosphere in accordance with the Moon's lighting.

SHADOW_CASCADE_MODE#

Name	Description
SHADOW_CASCADE_MODE_DYNAMIC = 0	Dynamic shadow cascade generation mode. In this mode shadow cascades are built dynamically relative to the camera's position. All shadows are calculated dynamically making it possible to change the time of day (day-night cycle).
SHADOW_CASCADE_MODE_STATIC = 1	Static shadow cascade generation mode. In this mode shadow cascades are built and baked relative to the light source's position. This mode is suitable as a performance optimization technique for small-area ArchViz projects where shadow cascades can be divided into 2 sections: walkable area with high-resolution shadows (as they're observed closely) and non-walkable area with low-resolution shadows (as they're observed from a distance). Notice Changing the time of day is not available in this mode, as shadow cascades are baked.

Name

Description

SHADOW_CASCADE_MODE_DYNAMIC = 0

Dynamic shadow cascade generation mode. In this mode shadow cascades are built dynamically relative to the camera's position. All shadows are calculated dynamically making it possible to change the time of day (day-night cycle).

SHADOW_CASCADE_MODE_STATIC = 1

Static shadow cascade generation mode. In this mode shadow cascades are built and baked relative to the light source's position. This mode is suitable as a performance optimization technique for small-area ArchViz projects where shadow cascades can be divided into 2 sections: walkable area with high-resolution shadows (as they're observed closely) and non-walkable area with low-resolution shadows (as they're observed from a distance).

NoticeChanging the time of day is not available in this mode, as shadow cascades are baked.

Members

static LightWorldPtr create ( const Math::vec4 & color ) #

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

Arguments

const Math::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 MODE_* variables.

int getMode ( ) const#

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 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 ( ) const#

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 ( ) const#

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 ( LightWorld::SCATTERING scattering ) #

Sets a lighting type for the world light.

Arguments

LightWorld::SCATTERING scattering - One of the SCATTERING_* variables.

LightWorld::SCATTERING getScattering ( ) const#

Returns a lighting type set for the world light.

Return value

One of the SCATTERING_* variables.

void setShadowCascadeMode ( LightWorld::SHADOW_CASCADE_MODE 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

LightWorld::SHADOW_CASCADE_MODE mode - Shadow cascade mode, one of the SHADOW_CASCADE_MODE_* variables.

LightWorld::SHADOW_CASCADE_MODE getShadowCascadeMode ( ) const#

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 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 ) const#

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.

Notice