General

The VRaySun and VRaySky are special features which are provided by the V-Ray renderer. Developed to work together, the VRaySun and VRaySky 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 VRaySun.

 

The V-Ray Sun and Sky are based largely on the model presented in [1]. For a more complete list of references, please see the References and links section.

VRaySun parameters

The VRaySun is located in the (Create - Lights - VRay) panel. You can also specify the VRaySun as the sun type inside a 3ds Max Daylight system.

 

Enabled - turns on and off the sun light.

 

Invisible - when on, this option makes the sun invisible, both to the camera and to reflections. This is useful to prevent bright speckles on glossy surfaces where a ray with low probability hits the extremely bright sun disk.

 

Turbidity - this parameter 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. For further info, please see the section.

 

Ozone - this parameter 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. For further info, please see the  section.

 

Intensity multiplier - this is an intensity multiplier for the VRaySun. Since the sun is very bright by default, you can use this parameter to reduce its effect. See the  and  sections for more information.

 

Size multiplier - this parameter 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. For further information, please see the section.

 

Shadow subdivs - this controls the number of samples for the area shadow of the sun. More subdivs produce area shadows with better quality but render slower. For further info, please see the section.

 

Shadow bias - moves the shadow toward or away from the shadow-casting object (or objects). If the bias value is too low, shadows can "leak" through places they shouldn't, produce moire patterns or making out-of-place dark areas on meshes. If bias is too high, shadows can "detach" from an object. If the bias value is too extreme in either direction, shadows might not be rendered at all. For further info, please see the section.

 

Photon emit radius - determines the radius of the area, in where photons would be shot. This area is represented by the green cyllinder around the Sun's ray vector. This parameter has effect when photons are used in the GI solutions or caustics. 

Sky Model - Allows you to specify the procedural model that will be used to generate the VRaySky texture.

 

- Preetham et al. - when this mode is selected the VRaySky procedural texture will be generated based on the Preetham et al. method. 

- CIE Clear - when this mode is selected the VRaySky procedural texture will be generated based on the CIE method for clear sky. 

- CIE Overcast - when this mode is selected the VRaySky procedural texture will be generated based on the CIE method for cloudy sky

 

 

Indirect horiz. illum. - specifies the intensity (in lx) of the illumination on horizontal surfaces coming from the sky

 

Exclude - this button allows you to exclude objects from illumination/shadow casting for the sun light.

VRaySky parameters

The VRaySky texture map is typically used as an environment map, either in the 3dsmaxEnvironment dialog, or in one of the slots of the V-Ray Environment rollout and behaves very much like a HDRI environment map. The VRaySkychanges its appearance based on the position of the VRaySun.

 

Manual sun node - specifies how the VRaySkydetemines its parameters: 

Off - the VRaySky will automatically take its parameters from the first enabled VRaySun in the scene. In this case, none of the other parameters of VRaySky are accessible.

 

On - you can choose a different light source. It is recommended that you choose only direct lights, as the vector for the direction is taken into consideration when computing the appearance of the sky. In that case theVRaySun is no longer controlling the VRaySky and the parameters in the texture map rollout determine the final look of the sky.

 

Sun node - specifies which light source is chosen if Specify sun node is On.

 

Sun turbidity - refer to VRaySun parameters

 

Sun ozone - refer to VRaySun parameters

 

Sun intensity multiplier - refer to VRaySun parameters

 

Sun size multiplier - refer to VRaySun parameters

 

Sun invisible - when this option is on, the sun disk will not be visible on the sky texture.

Sky Model - Allows you to specify the procedural model that will be used to generate the VRaySky texture.

 

- Preetham et al. - when this mode is selected the VRaySky procedural texture will be generated based on the Preetham et al. method. 

- CIE Clear - when this mode is selected the VRaySky procedural texture will be generated based on the CIE method for clear sky. 

- CIE Overcast - when this mode is selected the VRaySky procedural texture will be generated based on the CIE method for cloudy sky

 

 

Indirect horiz. illum. - specifies the intensity (in lx) of the illumination on horizontal surfaces coming from the sky

Notes

• By default, the VRaySun and VRaySky are very bright. In the real world, the average solar irradiance is about 1000 W/m^2 (see the references below). Since the image output in V-Ray is in W/m^2/sr, you will typically find that the average RGB values produces by the sun and the sky are about 200.0-300.0 units. This is quite correct from a physical point of view, but is not enough for a nice image. You can either useColor mapping to bring these values to a smaller range (which is the preferred way) or you can use the Sun intensity multiplier to make the sun and sky less bright. Using the VRayPhysicalCamera with suitable values also produces a correct result without changing the sun and sky parameters.