Sky Interface¶

class simul::sky::SiderealSkyInterface¶

An abstract interface class for a sky that is calculated using sidereal data.

Subclassed by simul::sky::SiderealSky

Public Functions

virtual const float *SiderealToEarthMatrix(double epoch_time, float latitude, float longitude) const = 0¶: Get a 4x4 transformation matrix to transform sidereal coordinates into azimuth and elevation.

class simul::sky::OpticalLengthInterface¶

An abstract interface class for skies that can calculate optical lengths.

Subclassed by simul::sky::Sky

Public Functions

virtual float GetOpticalLength(float Elevation, float h_km) const = 0¶: Get the effective optical length (equivalent length at sea level density) of a ray cast from altitude h_km at angle Elevation above the horizon.

virtual float GetHazeFactorOpticalLength(float Elevation, float h_km, HazeStruct hazeStruct) const = 0¶: Get the effective optical length of haze of a ray cast from altitude h_km at angle Elevation above the horizon.

virtual float GetOzoneOpticalLength(float Elevation, float h_km) const = 0¶: Get the effective optical length of ozone of a ray cast from altitude h_km at angle Elevation above the horizon.

class simul::sky::BaseSkyInterface¶

An abstract interface class for skies.

Subclassed by simul::sky::SkyKeyframer

Public Functions

Wavelengths in blue These values are used to calculate the Mie coefficients is MieWavelengthExponent is non and the Rayleigh coefficients if CalcAutomaticRayleighCoefficients is called VIRTUAL_Get (float, MieEccentricity,"Eccentricity of Mie (haze) scattering in the sky.") virtual vec3 GetDirectionToLight(double t: Get the direction to the current strongest light source - could be the sun or the moon.

virtual vec3 GetDirectionToLight(float altitude_km) const = 0¶: Get the direction to the current strongest light source - could be the sun or the moon.

virtual vec3 GetDirectionToSun() const = 0¶: Get the current direction to the sun.

virtual vec3 GetDirectionToSun(double t) const = 0¶: Get the direction to the Sun at the given time.

virtual vec3 GetDirectionToMoon(sky::uid = 0) const = 0¶: Get the current direction to the Moon.

virtual vec3 GetDirectionToMoon(sky::uid, double t) const = 0¶: Get the direction to the Moon at the given time.

virtual vec3 GetLocalSunIrradiance(double t, float altitude_km) const = 0¶: Get the sunlight that reaches the altitude altitude_km.

virtual float4 GetLocalIrradiance(float altitude_km) const = 0¶: Get the sunlight that reaches the altitude altitude_km.

virtual float4 GetMieRayleighRatio() const = 0¶: Get the ratio of Mie to Rayleigh scattering at unit air and haze density. A useful helper function as some shaders use this ratio.

virtual vec3 GetSunlightTableTransformKm() const = 0¶: Get the transform vector to convert an altitude in km into a 1D texture coordinate for the sunlight table. x = multiplier, y=offset, so texcoord u=t.x*zkm+t.y;.

virtual float GetHorizonElevation(float h_km) const = 0¶: Get the horizon elevation from a given altitude.

virtual EarthShadow GetEarthShadow(float h_km, const vec3 &lightDir) const = 0¶: The Earth’s shadow, as seen from the given altitude.

virtual float4 GetInscatterAngularMultiplier(float cosine, float mie_factor, float alt_km) const = 0¶: Get the multiplier for an inscatter factor that gives the total inscatter, where cosine is the cosine between the angle to the sun and the ray direction, mie_factor is the proportional haze factor (stored int the w element of the inscatter factor) and alt_km is the viewing altitude in km.

virtual float GetVisibilityDistance(float view_alt_km) = 0¶: From the altitude specified, the distance in km to 10% visibility (mainly a factor of fog/haze).

virtual float GetHazeForVisibilityDistance(float view_alt_km, float horiz_dist_km) = 0¶: Get the haze that will produce the required visibility distance in the horizontal direction.

virtual float GetTemperatureKelvins(float h_km) const = 0¶: Return the temperature at the stated altitude in kelvins (subtract 273.15 to get celsius).

virtual unsigned GetSubdivisionChecksum() const = 0¶: When this checksum changes, the atmosphere has been modified sufficiently to warrant regeneration of tables.

class simul::sky::AtmosphericScatteringInterface¶

An abstract interface class for skies.

Subclassed by simul::sky::Sky

General <br>

virtual float GetMoonIrradianceFactor(const Moon &m, const vec3 &dir_to_moon, const vec3 &dir_to_sun) const = 0¶: Get the moonlight irradiance in space.

virtual vec3 GetLocalMoonIrradianceFactor(const Moon &m, float altitude_km, const vec3 &dir_to_moon, const vec3 &dir_to_sun, HazeStruct hazeStruct) const = 0¶: Get the moonlight that reaches the altitude altitude_km.

virtual vec3 GetLocalSunIrradiance(float altitude_km, const vec3 &sun_irradiance, const vec3 &dir_to_sun, HazeStruct hazeStruct) const = 0¶: Get the sunlight that reaches the altitude altitude_km.

virtual float4 GetColourLossFactor(const vec3 &view_pos_km, const vec3 &pos_km, HazeStruct hazeStruct, bool earth_test = false, int steps = 0) const = 0¶

Get the loss factor of an object at position pos_km seen from view_pos_km.

When an object has initial colour c, multiply each member of c by the corresponding member of the loss factor to get the colour as seen by the viewer.

virtual EarthShadow GetEarthShadow(float h_km, const vec3 &lightDir) const = 0¶: The Earth’s shadow, as seen from the given altitude.

virtual float4 GetIsotropicColourLossFactor(float alt_km, float elevation, float min_dist_km, float max_dist_km, HazeStruct hazeStruct, bool earth_test = false, int steps = 0, bool blackbody = false, float emissivity = 0.f) const = 0¶: Get the loss factor of an object at position pos_km seen from view_pos_km. When an object has initial colour c, multiply each member of c by the corresponding member of the loss factor to get the colour as seen by the viewer.

virtual float4 GetAnisotropicInscatterFactor(bool include_sunlight, float alt_km, float elevation, float min_dist_km, float max_dist_km, const vec3 &sun_irradiance, vec3 moon_albedo, const float4 &starlight, const vec3 &dir_to_sun, const std::map<uid, vec3> &moonDirections, HazeStruct hazeStruct, float4 wavelengthsNm, const OvercastStruct &overcast, bool earth_test, int steps) const = 0¶: Get the inscatter factor in the xyz - the 3-element factor which is multiplied by the 3-element factor Beta to get the inscattered colour. In the w element is the haze factor. This excludes skylight and starlight, which are not considered to be strongly anisotropic. See GetIsotropicInscatter().

virtual float4 GetIsotropicInscatter(float alt_km, float elevation, float min_dist_km, float max_dist_km, const vec3 &sun_irradiance, vec3 moon_albedo, const float4 &starlight, const vec3 &dir_to_sun, const std::map<uid, vec3> &moonDirections, HazeStruct hazeStruct, float4 wavelengthsNm, const OvercastStruct &overcast, bool earth_test = false, int steps = 0) const = 0¶: Get the approximate isotropic inscatter, i.e. the inscatter without a dependence on the angle to the strongest light source. In particular, this includes skylight and starlight.

virtual float4 GetBlackbodyInscatter(float alt_km, float elevation, float min_dist_km, float max_dist_km, const vec3 &sun_irradiance, vec3 moon_albedo, const float4 &starlight, const vec3 &dir_to_sun, const std::map<uid, vec3> &moonDirections, HazeStruct hazeStruct, float4 wavelengthsNm, bool earth_test = false, int steps = 0, float emissivity = 0.f) const = 0¶: Get the radiance due to blackbody radiation.

virtual float4 GetInscatterAngularMultiplier(float cosine, float mie_factor, HazeStruct hazeStruct) const = 0¶: Get the multiplier for an inscatter factor that gives the total inscatter, where cosine is the cosine between the angle to the sun and the ray direction, mie_factor is the proportional haze factor (stored int the w element of the inscatter factor) and alt_km is the viewing altitude in km.

virtual float GetVisibilityDistance(float view_alt_km, HazeStruct hazeStruct) = 0¶: From the altitude specified, the distance in km to 10% visibility (mainly a factor of fog/haze).

virtual float GetHazeForVisibilityDistance(float view_alt_km, float horiz_dist_km, HazeStruct hazeStruct) = 0¶: Get the haze that will produce the required visibility distance in the horizontal direction.

virtual float GetOzoneAtAltitude(float alt_km) const = 0¶: Get the amount of ozone present at altitude alt_km. This is a dimensionless number.

virtual float GetHazeFactorAtAltitude(float alt_km, HazeStruct hazeStruct) const = 0¶: Get the amount of haze present at altitude alt_km compared to the amount at sea level. This value is independent of the overall Haze multiplier ( see GetHaze() ).

virtual float GetOvercastAtAltitude(const OvercastStruct &overcast, float alt_km) const = 0¶: Get the strength of the overcast effect at a given altitude, determined by Overcast, OvercastBaseKm, and OvercastRangeKm.

virtual float4 GetSunlightFactor(float alt_km, const vec3 &DirectionToLight, HazeStruct hazeStruct) const = 0¶: Return the colour of sunlight passing through the stated altitude as a multiplier of the sun radiance in space.

virtual float GetDistanceToSpace(float Elevation, float h_km) const = 0¶: Considering the atmosphere as a shell of thickness GetAtmosphereThickness(), from altitude h_km, this function returns how far a ray cast at angle Elevation above the horizon would travel to reach the outer radius of the shell.

virtual float GetDistanceToEarth(float Elevation, float h_km) const = 0¶: From the specified altitude h_km, and in the direction of Elevation, how far is it in Km to the surface?

Public Functions

VIRTUAL_GetAndSet (float, PlanetRadius,"Radius of the planet, default 6378 km (Earth)") VIRTUAL_GetAndSet(float: Calculate Rayleigh coefficients for air using colour wavelengths ColourWavelengthsNm.

struct HazeStruct¶: A data structure to contain haze properties in the atmosphere at any given moment.

struct OvercastStruct¶

struct LightingState¶

struct simul::sky::EarthShadow¶

Properties of the Earth’s shadow on the atmosphere and other objects.

Public Members

bool enable¶: If true, the Earth’s shadow should be visible above the horizon.

vec3 normal¶: normal is the direction normal to the sunlight direction

float radius_on_cylinder¶: radius_on_cylinder is the distance from the Earth’s centre to the viewpoint on the plane of the cylinder

float illumination_altitude¶: What altitude (in km) is the lowest that sunlight reaches, directly above/below the viewer.

float planet_radius¶: In km.

float terminator_distance_km¶: The shortest distance from the viewer TO the terminator, which will be in the direction TO the sun.

struct Orbit¶

struct Moon¶