Dome Light

A Dome light shines inward at the scene as if from a spherical or hemispherical light source outside the scene extents. This light is frequently used for Image-Based lighting (IBL) using panoramic High Dynamic Range Images (HDRIs) as environments. HDRIs with a Dome light can create realistic lighting and environmental reflections.

A Dome light's illumination comes from a hemispherical dome above the y-axis of the light or as a full sphere.

Certain parameters are only available as node inputs for the Light Dome. 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 rotation and scale of the light.

Pivot Offset – Allows a vector-outputting node to be connected to control the pivot of the light. Alternatively, they can be set manually.

Dome Color (input socket) – Overrides the color of the light, regardless if Color Mode is set to Color or Temperature.

Shadow Color (input socket) – Overrides the Shadow Color and allows a texture to be connected to control that property.

Intensity Tex (input socket) – Allows an integer-outputting node to be connected to control the Intensity.

Enabled – Turns the Dome Light on and off.

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

Color 1 – Specifies the color of the light rays and of the light source itself when visible in renderings.

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

Units – Choose the light units. Using the correct units is essential when using the V-Ray Physical Camera. The light automatically takes the scene's unit scale into consideration to produce the correct result for the scale you are working with. The possible values are:

Default – The color and multiplier directly determine the visible color of the light without any conversion. The light surface appears with the given color in the final image when seen directly by the camera (assuming there is no color mapping involved).
Lumens – Total emitted visible light power measured in lumens. When this setting is used, the intensity of the light does not depend on its size. A typical 100W electric bulb emits about 1500 lumens of light. Note that V-Ray uses a conversion unit of 683 lum/watt, that is, the maximum physical possible Luminous efficacy.
lm/m/m/sr – Visible light surface power measured in lumens per square meter per steradian. When this setting is used, the intensity of the light depends on its size.
Watts – Total emitted visible light power measured in watts. With this setting, the intensity of the light does not depend on its size. Keep in mind that this is not the same as the electric power consumed by a light bulb, for example. A typical 100W light bulb only emits between 2 and 3 watts of visible light. Note that V-Ray uses a conversion unit of 683 lum/watt, that is, the maximum physical possible Luminous efficacy.
w/m/m/sr – Visible light surface power measured in watts per square meter per steradian. When this setting is used, the intensity of the light depends on its size. 

Intensity – Multiplier for the light Color.

Dome Spherical – When enabled (the default), the Dome Light covers the entire sphere around the scene. When disabled, the light covers a hemisphere only.

Dome Adaptive – Speeds up the rendering by optimizing the sampling algorithm for the dome light. No light portals are needed with this setup. Light Cache must be set as the GI engine for this feature.

Finite Dome – When enabled, changes the way the Dome Light is calculated so that it emulates a dome with a physical size in the scene. This is useful when we need to introduce some parallax for the background when moving the camera and projecting the light texture on the ground. The finite dome consists of a ground plane, a hemispherical upper part, and a transition area between the two.

Finite Radius – Determines the radius of the Finite Dome.

Projection Height – Offsets the height of the environment map projection.

Finite GroundBlend – Controls the transition between the ground plane and the hemispherical upper part of the Finite Dome. A value of 0.0 means a sharp transition, whereas 1.0 means that the dome morphs into a sphere. Intermediate values blend between the two.

Lock Texture to Dome – 

Invisible – Controls whether the shape of the light source is visible in the resulting render. When disabled, the source light is rendered in the current light color; otherwise, the light source itself is not visible in the scene. The Invisible attribute only affects the visibility of the light when seen directly by the camera or through refractions. The Affect Specular controls the visibility of the light with respect to reflections and Affect Reflections options.

Affect Diffuse – Determines whether the light affects the diffuse properties of the materials. With this option off, there is no diffuse contribution from the light.

Affect Specular – Determines whether the light affects the specular of the materials (i.e., glossy reflections). With this option off, there is no specular contribution from the light.

Affect Reflections – Determines whether the light appears in reflections of materials for both perfect and glossy reflections.

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

Affect Alpha – Determines whether or not the Dome Light is visible in the Alpha channel of the render. When enabled, you have a white alpha where the background is visible. When disabled, you have black alpha where the background is visible.

Diffuse Contribution – A multiplier for the effect of the light's diffuse contribution on a surface.

Specular Contribution – A multiplier for the effect of the light on the specular of the surface.

Atmospherics Contribution – Determines the amount of influence the light has on the atmospheric effects. This option is not available with V-Ray GPU.

Cut-off Threshold –  Specifies a threshold for the light intensity below which the light is not computed. This can be useful in scenes with many lights, where you want to limit the effect of the lights to some distance around them. Larger values cut away more from the light; lower values make the light range larger. If you specify a value of 0.0, the light is calculated for all surfaces. This option is not available with V-Ray GPU.

Texture Resolution – Specifies the resolution at which the texture is resampled for importance sampling.

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 default), the light casts shadows. Disable this option to turn off shadows for the light.

Shadow Bias – Moves the shadow toward or away from the shadow-casting object (or objects). Higher values move the shadow toward the object(s), 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.

Shadow Color – Controls the color of shadows for this light. Note that anything different from black is not physically correct. This option is inactive when using the V-Ray CUDA engine.

This rollout is not available with V-Ray GPU.

Photon Target Radius – Defines a sphere around the light icon where photons are being shot when photon-mapped caustics or the global photon map are used.

Emit Distance – Defines a sphere around the light icon, from which photons are being shot towards the target radius area.

Caustics Subdivs – Only used when calculating Caustics. Lower values mean more noisy results but render faster. Higher values produce smoother results but take more time.

Caustics Multiplier – This value is a multiplier for the generated caustics by the selected object. Note that this multiplier is cumulative - it does not override the multiplier in the Caustics settings.