SunLight

V-Ray Sun and V-Ray Sky are special features which are provided by V-Ray renderer. Developed to work together, V-Ray Sun and V-Ray Sky reproduce the real-life Sun and Sky environment of the Earth. Both are coded so that they change their appearance depending on the direction of V-Ray Sun.

The V-Ray Sun and Sky are based largely on SIGGRAPH '99 paper "A Practical Analytic Model for Daylight" by A. J. Preetham, Peter Shirley, Brian Smits. For a complete list of references, please see the References section.

Sun light has some unique qualities:

• Sun light rays that strike the scene objects are treated as parallel to one another regardless of how far the Sun object is placed from the scene objects, producing the parallel shadows that our own sun creates.

• Sun light is designed to be used with global illumination. When the light bounces around the scene, the resulting rendering looks like sunlight in real life.

• If you are using GI, use Sun light with Sky environment background to provide realistic lighting and coloring for the scene. Often, Sun/Sky is the only lighting setup needed in the scene to produce a photoreal rendering.

• The Sun/Sky combination is suitable for an exterior scene or for an interior scene with windows or other openings through which the light comes.

Enabled () – Turns SunLight on and off.

Custom Orientation

Custom Orientation – Enables custom orientation.

Horizontal Angle – Controls the custom sun azimuth angle (horizontal rotation).

Vertical Angle – Controls the custom sun altitude angle (vertical rotation).

Color – Shifts the hue of SunLight system towards the color specified in the field.

Color Mode – Affects the way the color in the Filter color parameter affects the color of the sun.

Filter – Shifts V-Ray sun's hue according to the Filter Color parameter. 
Direct – Sets the color of V-Ray sun to the color in the Filter Color parameter. The intensity of the light no longer depends on the position of V-Ray Sun in the sky. Instead, intensity is controlled through the Intensity Multiplier. 
Override – Sets the color of V-Ray sun to the color in the Filter Color parameter. The intensity of the light still depends on the position of V-Ray Sun in the sky.

Intensity Multiplier – Affects the brightness of the sun and can be used to reduce the default brightness. See Notes for more information. See the Intensity Multiplier example.

Size Multiplier – Affects the visible size of the sun. This includes the appearance of the sun disc as seen by the camera and of the reflections, as well as the blurriness of the sun shadows. See the Size Multiplier example.

Sky Model – Specifies the procedural model that is used to generate V-Ray Sky texture.

Preetham et al. – V-Ray Sky procedural texture is generated based on the Preetham et al. method.
CIE Clear – V-Ray Sky procedural texture is generated based on the CIE method for clear sky. 
CIE Overcast – V-Ray Sky procedural texture is generated based on the CIE method for cloudy sky.
Hosek et al. – V-Ray Sky procedural texture is generated based on the Hosek et al. method.
PRG Clear Sky – V-Ray Sky procedural texture is generated based on the PRG Clear Sky method which has enhanced sunrise and sunset sky. See the PRG Clear Sky example.

Horizon Illum. – Specifies the intensity (in lx) of the illumination on horizontal surfaces coming from the sky.

Altitude – Controls the observer's altitude in meters. As the altitude increases, sky clarity improves, and the horizon line becomes less defined. See the Altitude example.

Turbidity  – Determines the amount of dust in the air and affects the color of the sun and sky. Smaller values produce a clear, blue sky and sun as seen in rural areas, while larger values make them yellow and orange as seen in big cities. This parameter is inactive when the Sky Model is set to PRG. See the Turbidity example.

Ozone – Affects the color of the light. Values closer to 0.0 make the sunlight yellow, and values closer to 1.0 make it blue. This parameter is inactive when the Sky Model is set to PRG. See the Ozone example.

Albedo Color – Sets the ground color of the V-Ray Sun and Sky system.

Blend Angle – Specifies the angle in degrees where blending occurs between the horizon line and sky. Values close to 0.0 produce a sharper horizon line, while larger values produce a softer horizon line.

Horizon Offset – Allows the user to manually lower the horizon line. 

Clouds () – Enables the clouds.

Density – Controls the clouds density. A higher value leads to more clouds. See the Density example.

Variety – Controls the cloud variety in space and shape. See the Variety example.

Cirrus Amount – Controls the amount of high-altitude cirrus clouds. See the Cirrus Amount example.

Height (m) – Controls the clouds height. See the  Height example.

Thickness (m) – Controls the clouds thickness. See the Thickness example.

Offset X (m) – Controls the offset in the X direction measured in meters.

Offset Y (m) – Controls the offset in the Y direction measured in meters.

Phase X (%) – Clouds phase in X direction specified in percentage (%).

Phase Y (%) – Clouds phase in Y direction specified in percentage (%).

Ground Shadows – Enables the clouds shadows, best suited for larger scenes. Note that it is recommended to use a Dome light with a Sky texture for high quality shadows. When disabled, a single shadow is cast over the entire scene depending on whether the sunlight reaching the camera position is blocked by a cloud. Disabling ground shadows is recommended for smaller scenes and may speed up the render process. See the Clouds Shadows example.

Contrails – When enabled, plane contrails are simulated in the sky.

Contrails Number – Determines the number of contrails generated. See the Contrails Number example below.
Contrails Strength – Determines the opacity of the contrails. Lower values create less opaque trails, which look older. See the Contrails Strength example below.
Contrails Distortion – Determines the amount of distortion in the contrails. See the Contrails Distortion example below.
Contrails Offset X (m) – Offsets the contrails by a given value. See the Contrails Offset example below. 
Contrails Offset Y (m) – Offsets the contrails by a given value.
Contrails Pace (%) – Determines how fast airplane contrails progress along the sky. A value of 100% represents an approximate airplane speed of 800km/h. A value of 0% makes the contrails static. Increasing this multiplier value makes contrails appear faster and persist in the sky for a shorter amount of time. See the Contrails Time example below.

Dynamic Clouds – Enables the automatic clouds formation. When enabled, the clouds use unique offset and phase values based on the current time of the day.

Wind Direction (deg) – Specifies the wind direction vector rotation in the horizontal plane. A value of 0 means that the clouds move in the positive X direction. Increasing the wind direction value horizontally rotate this vector clockwise.
Wind Speed (m/s) – Specifies the clouds movement speed measured in meters per seconds.
Phase Velocity (%/s) – Specifies the phase change measured in percent of the cycle per second. A value of 1 means that the phase loops to its initial state every 100 seconds. Smaller values result in slower changes and a longer phase loop.

Invisible – When enabled, the sun becomes invisible to both the camera and the reflections. This is useful to prevent bright speckles on glossy surfaces where a ray with low probability hits the bright Sun disk.

Shadows – When enabled (the default), V-Ray Sun casts shadows. When disabled, the light does not cast shadows.

Affect Diffuse – When enabled, V-Ray Sun affects the diffuse properties of the materials.

Affect Specular – When enabled, V-Ray Sun affects the specular of the materials.

Affect Atmospherics – Specifies whether the light influences the atmospheric effects in the scene. The value determines the amount of involvement.

Atmospheric Shadows – When enabled, the atmospheric effects in the scene cast shadows.

Caustic Photons

Caustic Subdivisions – Determines the number of caustic photons emitted from the light source. Lower values mean more noisy results but faster rendering. Higher values produce smoother results but take more time.

Emit Radius – Defines the area around the V-Ray Sun from where the photons are shot.