Table of Contents

This page includes details about the Sky texture used for the environment with V-Ray Sun.


Overview


The VRaySky texture map is typically used as an environment map to help simulate outdoor lighting. The texture changes its appearance based on the position of the V-Ray Sun, which it is normally used in conjunction with. 

When using the VRaySky texture in combination with the V-Ray Sun, it is recommended to use directly the V-Ray Sun and Sky system, which is automatically set when created.


UI PathTexture > V-Ray > VRaySky


 



General


Intensity Multiplier – Determines the intensity value when overwriting the Sun settings.

Turbidity – Determines the amount of dust in the air and affects the color of the Sun and Sky. Smaller values produce a clear and blue sky and sun as you get in the country, while larger values make them yellow and orange as, for example, in a big city.

Ozone – Affects the color of the sun light. Available in the range between 0.0 and 1.0. Smaller values make the sunlight more yellow, larger values make it blue.

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

Sky Model – Determines the procedural model that will be used to generate the VRaySky texture:

Hosek et al – When selected, the VRaySky procedural texture is generated based on the Hosek et al. method and uses a different ground and sky gradient.
Preetham et al. – When selected, the  VRaySky procedural texture is generated based on the Preetham et al. method.
CIE Clear
 
– When selected, the VRaySky procedural texture is generated based on the CIE method for clear sky.
CIE Overcast – When selected, the VRaySky procedural texture is generated based on the CIE method for cloudy sky.
PRG Clear Sky – This procedural texture is generated using the PRG Clear Sky method. The updated PRG Clear Sky method allows for rendering the sky at various observer altitudes, up to several kilometers. It also supports rendering nautical twilight effects with sun positions up to 12 degrees below the horizon. Additionally, it features enhanced turbidity control, enabling the rendering of sky conditions with turbidity values ranging from 1.81 to 4.89. See the PRG Clear Sky New examples below.


The PRG Clear Sky model in scenes created with V-Ray 7 cannot be rendered using previous V-Ray versions.


Horiz Illum – Specifies the intensity (in lx) of the illumination on horizontal surfaces coming from the sky.
Note: Only available when CIE Overcast or CIE Clear are selected as the Sky model.

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

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

FilterShifts the V-Ray sun's hue according to the Filter Color parameter. 
DirectSets 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. 
OverrideSets 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.

Filter ColorShifts the hue of the V-Ray Sun and Sky system towards the color specified in the field.

Ground Albedo – Sets the color of the V-Ray Sun and Sky system's ground.

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.

Water Vapour – Controls the amount of water vapor which affect the sky control.


Options


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 extremely bright sun disk. This option is currently not compatible with the PRG Clear Sky model.

Sun – Specifies the Sun object, to which the Sky is attached.

Sun Direction Only – When enabled, the sky texture does not attach to the Sun. Instead, it only considers the Sun object's direction.




Example: Sky Models


The examples below show the different Sky Model types, in these examples default values for VRaySky have been used.


Preetham et al.

CIE Clear

CIE Overcast

Hosek et al.

PRG Clear Sky







Example: PRG Clear Sky - Turbidity

In this example, you can see how the amount of dust in the air affects the color of the sun and sky. Smaller values produce a clear image, while higher values dim the sun and sky. 

Example: PRG Clear Sky - Nautical twilight effect

This example shows how the sun's position affects the sky, creating a twilight effect. Changing the sun's position could also require adjusting the Exposure of the V-Ray Physical Camera. In this example, Exposure Value is used for easier reading, but you can opt for Physical Exposure to be more physically accurate.



01_PRGNew_Turbidity-2

Turbidity = 2

02_PRGNew_Turbidity-2x6

Turbidity = 2.6

03_PRGNew_Turbidity-3

Turbidity = 3

04_PRGNew_Turbidity-4

Turbidity = 4

05_PRGNew_Turbidity-5

Turbidity = 5

01_PRGNew_EV10_0deg

Exposure Value = 10; Sun below the horizon = 0°

02_PRGNew_EV10_-2deg

Exposure Value = 10; Sun below the horizon = -2°

03_PRGNew_EV10_-4deg

Exposure Value = 10; Sun below the horizon = -4°




Example: PRG Clear Sky New - Altitude

This example shows how the Altitude values affect the visualization of the sky. Higher Altitude values result in better sky clarity and a less defined horizon line.


01_PRGNew_Altitude-0

Altitude = 0

02_PRGNew_Altitude-1000

Altitude = 1000

03_PRGNew_Altitude-2000

Altitude = 2000

04_PRGNew_Altitude-10000

Altitude = 10000

05_PRGNew_Altitude-15000

Altitude = 15000


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