Certain parameters are only available as node inputs for the Sun Light. For optimal editing, open the light in the V-Ray Node Editor. Follow these steps to see all the parameter locations for this node:

Click on the GIF to view it in full-size

This section describes the input sockets of the node. Some sockets have dedicated parameters, which are further described below, and some sockets are just inputs.

Transform – Allows a V-Ray Matrix node to be connected to determine the Sun Light's rotation and scale.

Ground albedo color (input socket) – Allows a color node to determine the Ground Albedo.

Shadow color (input socket) – Allows a color node to determine the Shadow Color.

Enabled – Turns the sun light on and off.

Intensity – Specifies the brightness of the sun. Since the sun is very bright by default, you can use this parameter to reduce its effect. This option is not available with V-Ray GPU.

Size – 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.

Color Mode – This mode affects the way V-Ray hues the sun and sky light.

Filter – Shifts the V-Ray Sun and Sky hue towards the color specified by either the Filter Color or the Temperature, depending on the Color Temp Mode.
Direct – Determines the V-Ray Sun light color either through the Filter Color or the Temperature, depending on the Color Temp Mode. In this case, the light intensity is controlled by the Intensity multiplier and it does not depend on the Sun's position in the sky.
Override – Determines the color of the Sun light through either the Filter Color or the Temperature, depending on the Color Temp Mode. However the intensity is controlled by the position of the V-Ray Sun in the sky. 

Color Temp Mode – Determines how the color of the light is controlled, either Color or Temperature.

Filter Color – When the Color Temp Mode is set to Color, shifts the hue of the V-Ray Sun and Sky system towards the specified color. This option is not available with V-Ray GPU.

Temperature – When the Color Temp Mode is set to Temperature, this parameter controls the color of the light by degrees Kelvin.

Sky Model – Determines the procedural model used to generate the V-Ray Sky texture:

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

Ground Albedo – Sets the color of the V-Ray Sun and Sky system's ground. A node can be connected to the input socket of this parameter. This option is not available with V-Ray GPU.

Horiz Illum – Specifies the intensity (in lx) of the illumination on horizontal surfaces coming from the sky. This parameter is enabled when one of the CIE Sky Models is selected. This option is not available with V-Ray GPU.

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. This option is not available with V-Ray GPU.

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

Turbidity – Determines the amount of dust in the air, which in turn affects the color of the sun and sky. Smaller values produce a clear, blue sky and sun similar to what is seen in rural areas, while larger values make the sun and sky more yellow and orange as seen in a big city. This option is not available with V-Ray GPU.

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, while larger values make it bluer. This option is not available with V-Ray GPU. This option is unavailable for the PRG Clear Sky model.

Altitude – Controls the observer's altitude in meters. As the altitude increases, sky clarity improves, and the horizon line becomes less defined. This option is only available for the PRG Clear Sky model.

Clouds On – Enables the cloud system.

Ground Shadows – When enabled, casts shadows from the clouds. See the Clouds Ground Shadows example for more information.

Density – Controls the density of the cumulus and stratus types of clouds. A value of 1 fills up the sky with clouds. See the Clouds Density example for more information.

Density Multiplier – A multiplier to the Density parameter. The larger the value, the darker the sky becomes at the horizon. Setting a value of 0 results in no clouds, regardless of the Density value.

Variety – Controls the variety of the cumulus and stratus types of clouds. See the Clouds Variety example for more information.

Seed – Generates a random value, based on the given number, to change the pattern of the clouds and the Contrails.

Cirrus Amount – The maximum value of 1 fills the sky with cirrus clouds. Decreasing the value, lowers the presence of such clouds. When set to 0, the cirrus clouds are completely gone. See the Clouds Cirrus Amount example for more information.

Height (m) – Determines the Clouds position in height. See the Clouds Height example for more information.

Thickness (m) – Lower values make the cumulus and stratus types of clouds thin and sheer/lucent, while higher values make them full and heavy. See the Clouds Thickness example for more information.

Longitude Offset (m) – Moves the cloud system by the X axis. See the Clouds Offset example for more information.

Latitude Offset (m) – Moves the cloud system by the Y axis. See the Clouds Offset example for more information.

Longitude Phase (%) – Controls the phase by the X axis, can be used to fine-tweak the cumulus and stratus clouds appearance. The appearance of the clouds loops at 0, 100, 200, etc. This parameter can be animated to resemble natural clouds appearance.

Latitude Phase (%) – Controls the phase by the Y axis. Can be used to fine-tweak the cumulus and stratus clouds appearance. The appearance of the clouds loops at 0, 100, 200, etc. This parameter can be animated to resemble natural clouds appearance.

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

Number of Contrails – Determines the number of contrails generated. See the Number of Contrails example for more information.

Contrails Strength – Determines the opacity of the contrails. Lower values create less opaque trails, which look older. See the Contrails Strength example for more information.

Contrails Distortion – Determines the amount of distortion in the contrails. See the Contrails Distortion example for more details.

Contrails Offset Longitude/Latitude (m) – Offsets the contrails by a given value, according to the X or Y axis. See the Contrails Offset example for more information.

Contrails Time – Determines how long along their way the planes are. See the Contrails Time animation for more details.

Example: Density

The Density parameter controls the number of clouds in the sky. The higher the value, the more clouds appear in the render. 

Move the slider to see the example renders.

Example: Variety

This example shows the effect of the Variety parameter on the clouds' distribution and look.

Move the slider to see the example renders.

Example: Cirrus Amount

This example shows how increasing the Cirrus Amount increases the appearance of the cirrus clouds in the render.

Move the slider to see the example renders.

Example: Height (m)

This example shows how the clouds change their position in the sky by increasing the Height (m) value.

Move the slider to see the example renders.

Example: Thickness (m)

The Thickness (m) parameter specifies how full the clouds are. Lower values make them thinner and sheerer, while higher values make them look heavy. 

Move the slider to see the example renders.

Example: Offset

The following example demonstrates how changing the Longitude Offset (m) and the Latitude Offset (m) parameters affects the appearance of the clouds.

Move the slider to see the example renders.

Example: Number of Contrails

Note that the contrails are spread randomly across the sky. In most cases, the camera does not capture all of the contrails.

Move the slider to see the example renders.

Example: Contrails Strength

This example shows how the Contrails Strength parameter makes the contrails more visible and prominent in the sky.

Move the slider to see the example renders.

Example: Contrails Distortion

The Contrails Distortion parameter is used to achieve some variety in the trace line. Move the slider to see the example renders.

Example: Contrails Offset

The Contrails Offset Longitude (m) and the Contrails Offset Latitude (m) options introduce an offset along the X or Y direction in the sky. Move the slider to see the example renders.

Invisible – When enabled, 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.

Affect Diffuse – Determines whether the Sun affects the diffuse properties of the materials.

Affect Specular – Determines whether the Sun affects the specular of the materials. The multiplier controls the sun's contribution to specular reflections.

Affect Atmospherics – When enabled, the light influences the atmospheric effects in the scene. This option is not available with V-Ray GPU.

Diffuse Contribution – Controls the Sun's contribution to the diffuse illumination.

Specular Contribution – Controls the Sun's contribution to the specular reflection.

Atmospherics Contribution – Determines the amount of influence the light has on the atmospheric effects.

LPE Label – Allows a label to be assigned, which can be used to reference the light in a Light Path Expression. This is especially useful when working with the Light Select render element to evaluate custom light contribution in the scene.

Shadows – When enabled, the objects in the scene cast shadows.

Shadow Color– Specifies a color or a texture map for the shadows. A node can also be connected to this parameter socket. This option is not available with V-Ray GPU.

Shadow Bias – Moves the shadow toward or away from the shadow-casting object. Higher values move the shadow toward the object, while lower values move it away. If this value is too extreme, shadows can "leak" through places they shouldn't or "detach" from an object. Other effects from extreme values include moire patterns, out-of-place dark areas on surfaces, and shadows not appearing at all in the rendering.

Atmos Shadows – When enabled, the atmospheric effects in the scene cast shadows. This option is not available with V-Ray GPU.

Photon Radius – Determines the radius of the area in which photons are shot. This area is represented by the cylinder around the Sun's ray vector. This parameter has an effect when photons are used in caustics.

Caustic Subdivs – Used by V-Ray when calculating Caustics. Lower values mean more noisy results but render faster. Higher values produce smoother results but take more time. This option is not available with V-Ray GPU.

Caustic Multiplier – Used by V-Ray when calculating Caustics. This multiplier controls the brightness of the caustics. This option is not available with V-Ray GPU.

The Include/Exclude rollout is used to create a list of objects that can be excluded (or included) from the light's effects, such as illumination or shadow casting. You can Exclude or Include objects by selecting the corresponding mode, or leave it at None to affect all objects in the scene.

From: – Determines the light effect that the objects are included/excluded from. You can apply this list to both Illumination/Shadow, or apply it only to Illumination or Shadow Casting.

You can add objects and collections by dragging and dropping them in this rollout or using the eyedropper tool . The selected items are displayed in the Objects List.