VRayLightDome

This page introduces the V-Ray Dome light, which is used for environment lighting as well as Image Based Lighting with HDRIs.

Overview

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) used as environments. HDRIs with a Dome light can create realistic lighting as well as environmental reflections.

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

^{Image courtesy of Andrew Jerez}

UI Paths

||V-Ray Shelf|| > VRayLightDome button

Create menu > Lights > V-Ray Dome Light

Basic Parameters

Enabled – Turns the VRayLightDome on and off.

Color Mode – Selects the mode in which the color of the light will be specified, either Color or Temperature.

Light Color – When Color Mode is set to Color, this parameter controls the color of the light. When using photometric units, this color is normalized so that only the color hue is used, whereas the light's intensity is set by the Intensity multiplier.

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

Intensity multiplier – 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 optimising 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.

Parameters - Texture

Use Dome Tex – When enabled, the light uses a texture for the VRayLightDome surface.

Multiply By The Light Color – Causes the colors in the texture to be multiplied by the light intensity.

Dome Tex – Specifies an environment texture for the VRayLightDome object. Note: If an RGBA texture file (a file that contains an alpha channel) is used, the file's alpha output must be connected to the Dome Tex A attribute to utilize the alpha channel on the light.

Dome Tex A – Specifies an alpha texture for the dome light. Note: The default value of 1 (fully opaque) remains unchanged whenever a file texture is connected to the Dome Tex attribute, even if that file contains an alpha channel. For a file's alpha channel to be utilized, it's alpha output needs to be connected to this attribute.

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

Tex Adaptive – When enabled, V-Ray adjusts the number of samples taken for different parts of the texture depending on their brightness.

Parameters - Viewport Display

Show in Viewport – Displays the texture loaded in the Dome Tex slot of the dome light as the environment in the viewport. You can disable the preview, preview only the texture, or preview the texture multiplied by the dome light's intensity.

Disabled – Disables Viewport Preview.
Texture Only – The specified texture will be previewed in the viewport.
Texture Intensity – The specified texture multiplied by the light's intensity.

Hardware texture res. – Specifies the resolution at which the texture will be previewed in the viewport.

Sphere object detail – Controls the number of faces used to display the sphere in the viewport.

Convert to sRGB color space – When enabled, the environment texture will automatically be converted to the sRGB color space. This only affects the preview in the viewport.

Gamma – Specifies a gamma value to be applied to the environment texture in the viewport when the Convert to sRGB color space option is disabled.

Note: The Gamma attribute only affects the preview of the texture in the viewport.

Parameters - Options

Invisible – Controls whether the shape of the VRayLight 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.

Note: The Invisible attribute only affects the visibility of the light when seen directly by the camera or through refractions. The visibility of the light with respect to reflections is controlled by the Affect Specular and Affect Reflections options.

Store With Irradiance Map – When enabled and GI calculation is set to Irradiance map, V-Ray will calculate the effects of the VRayLight and store them in the irradiance map. This results in the irradiance map being computed more slowly, but the rendering itself will take less time. You can also save the irradiance map and reuse it later.

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

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

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

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

Parameters - Sampling

Subdivs – This parameter is disabled by default since most users will not need local control of subdivs, however, this parameter controls the number of samples V-Ray takes to compute lighting locally for this light. Lower values create more noise but render faster. Higher values produce smoother results but take more time to render. Note that the actual number of samples also depends on the Sampler settings. By default, this parameter is controlled by the Min Shading Rate in the image sampler.

To activate this parameter and specify a value, use the Use Local Subdivs parameter under the V-Ray > DMC Sampler tab in the Render Settings window. This parameter is not available when the renderer is set to CUDA.

Light cutoff threshold – Specifies a threshold for the light intensity, below which the light will not be 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 will be calculated for all surfaces. This parameter is not available when the renderer is set to CUDA.

Parameters - Shadows

Shadows – Enables or disables the tracing of shadows.

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 – A multiplier for the shadows color. This option is inactive when the renderer is set to V-Ray CUDA.

Parameters - Photon Emission

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

Caustics subdivs – Used by V-Ray when calculating Caustics. Lower values mean more noisy results, but faster render. Higher values produce smoother results but take more time to render. This option is inactive when the renderer is set to V-Ray CUDA.

Caustics multiplier – 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 render roll-out section. This option is inactive when the renderer is set to V-Ray CUDA.

Photon Subdivs and Diffuse Multiplier parameters no longer show in the UI, as they are related to the Photon Map GI engine, which is deprecated. They are still accessible through script.

Parameters - UI Scale

Locator Scale – Multiplies the size of the locator in the viewport. This does not affect the render.

Parameters - Advanced Options

These options do not generally need to be changed. They are used in very very specific situations.

Use Ray Distance – Specifies the maximum distance to which shadow rays are going to be traced.

Ray Distance – Specifies the Ray distance in scene units.

Use MIS – Enables of disables Multiple Importance Sampling (MIS) for the light. When MIS is enabled (the default), the light's contribution is split between direct illumination, on the one hand, and GI (for diffuse materials) or reflections (for glossy surfaces) on the other. This means that portions of the light's contribution will end up in the GI render elements (or the reflection render elements respectively). In certain specific situations, this is undesirable and this option can be used to always calculate the light contribution through direct illumination.

Disabling MIS may increase noise, especially in glossy reflections. Please only disable this setting when you have a reason.

Example: IBL (Image-Based Lighting)

The V-Ray dome light supports arbitrary texture maps that determine the amount of light coming from each direction on the virtual dome hemisphere. V-Ray then uses importance sampling to trace more rays in the directions where most of the light is coming from. This ensures speed and quality that were never before possible with pure gathering GI methods.

Easy setup for image-based lighting (IBL);
Importance sampling of the dome texture for fast and clean results;
Support for photon mapping for fast and accurate caustic effects.

In the following example, we will show how this works with an HDR image.

Initial position of the dome-light.
The Y axis is perpendicular to the ground plane.

Rendered image

Position 1
This time the dome is rotated along its Y axis to 90 degrees. Notice this has no effect, as the dome is using the same part of the HDRI.

Rendered image

Position 2
The dome is rotated along its X axis to 90 degrees. Now the dome uses another part of the HDRI.

Rendered image

Now we are going to show how rotating the HDRI can also affect the rendered image. We will rotate the HDRI from the Hypershade by selecting the VRayPlaceEnvTex node.

The default position of the Dome Light.
Rotating the HDRI to -90 degrees. Now the dome obviously uses some of its the darker areas.