Sky

V-Ray Sky is a special feature provided by the V-Ray renderer to work with the V-Ray Sun. 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 the V-Ray Sun.

When the V-Ray Sun and Sky systems are connected together, they share a number of parameters. For example, changes made to the Sun section of the Sky Texture directly affect the V-Ray Sun. See the SunLight page.

Sun – Specifies the V-Ray Sun node that is used for the Sky texture creation. The Sun orientation (position) affects the Sky gradient. The following parameters affect this specific Sun light.

Custom Orientation

Enable – Enables custom orientation.

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

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

Color and Intensity

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

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

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

Intensity Multiplier – Determines the brightness of the sun and can be used to reduce the default brightness. 

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

Sky

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

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

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

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 a big city's atmosphere.

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.

Ground Albedo

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

Clouds () – Enables the clouds.

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

Variety – Controls the cloud variety in space and shape.

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

Height (m) – Controls the clouds height.

Thickness (m) – Controls the clouds thickness.

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 cloud shadows. Note that it is recommended to use a Dome light with a Sky texture for high quality shadows.

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 reflections. This is useful to prevent bright speckles on glossy surfaces where a ray with low probability hits the extremely bright sun disk.

Shadows – When enabled, the Sun produces shadows. 

Affect Diffuse – When enabled, the V-Ray Sun affects the diffuse properties of the materials. The slider sets the multiplier that controls the V-Ray Sun's contribution to the diffuse illumination.

Affect Specular – When enabled, the V-Ray Sun affects the specular of the materials. The slider sets the multiplier that controls the V-Ray Sun's contribution to the specular reflection.

Caustic Photons

Caustic Subdivisions – Determines the number of caustic photons emitted from the light source. Lower values produce noisy results, but render faster. 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.