This simulates light from a sphere or dome above the scene, representing the sky. It can also be used with high dynamic range (HDR) images to perform image-based environment lighting. This is the node which is typically used for lighting exterior scenes. 

This light is designed for outdoor scenes and is represented by a spherical dome in the background. Importance sampling will trace rays to specific directions of this dome. However, in an interior scene, most of these rays will hit an object, getting no contribution from the light at all and thus creating noise. In this situation, adding light_portals to the windows will help to reduce noise in an interior scene when using the skydome_light.


The skydome light is more efficient than the Sky shader for the following reasons:

  • The skydome light uses importance sampling to fire rays to bright spots in the environment, therefore automatically achieving both soft and sharp shadows; sampling the sky shader with GI rays cannot achieve hard shadows in reasonable times, you will need huge amounts of GI samples.
  • The environment map lookups for the skydome are cached rather than evaluated at render time. Since texture lookups via OIIO are very slow, this caching results in a nice speedup, usually 2-3x faster than uncached (if you are curious, you can switch to uncached lookups by setting options.enable_fast_importance_tables = false and measure the difference yourself).
  • The skydome is sampled with shadow rays, which can be faster than GI Diffuse rays because shadow rays only need to know that any hit blocks the light (rather than the first hit). This also means the sampling quality for the skydome is controlled via skydome_light.samples, whereas the quality for a background sky is controlled via the GI_{diffuse|glossy}_samples. This subtle distinction is very important: skydome is direct lighting and sampled with shadow rays, whereas the background sky shader is indirect lighting and therefore sampled with GI Diffuse rays.


As well as the settings that are common to all lights (except for Decay), the Skydome also has:

Color Type
Simple Color

Shows the RGB Color parameter.


Shows the Color Texture parameter. An HDR map can be connected here to use the skydome as Image Based Lighting.


Shows the Color Shader parameter with the path of a vopnet that is contained inside the skydome light for convenience.
A Physical Sky shader can be added inside this vopnet and connected to the color parameter of the Light Output.


The type of map being connected. It can be set to Lat-long (most common), Mirrored Ball or Angular.


The resolution controls the detail of reflections of the skydome. For most accurate results the Skydome light resolution must be set to match the HDRI image resolution, however, in many cases it can be set lower without a noticeable loss of detail in reflections. By default, the parameter is set to 1000. The higher the resolution parameter, the longer the skydome_light will take to precompute the importance tables for the light, which increases scene startup time.

The resolution parameter should be used with care. The higher the resolution value, the longer the skydome_light will take to pre-compute the importance map for that light. For high-resolution maps, this can be very slow.

Portal Mode

Defines how the skydome light interacts with light portals.

  • off: turns off portals.
  • interior_only: blocks any light outside portals for interior-only scenes.
  • interior_exterior: lets light outside portals through for mixed interior and exterior scenes.
Blocking light outside portals more predictably reduces noise for interior-only scenes.



By default, skydome lights are directly visible as a background. Lowering the influence of the light of camera rays makes them invisible to the camera, and makes the background transparent.


Per-light scaling for transmission. Should be left at 1 to produce physically accurate results.

Diffuse / Specular / SSS / Volume

Per-light scaling for Camera, Transmission, Diffuse, Specular, SSS, Indirect and Volume. Weights scaling the light contribution to each of those components independently. Should be left at 1 to produce physically accurate results.

Only Area lights and Point lights (non-0 radius) are visible to the camera. Camera and Transmission values default to 0 with Area lights.

Skydome Indirect Lighting

Outputs an indirect light AOV (the skydome_light outputs to direct light AOVs by default).


The Skydome light will not work with Atmosphere Volume. You must use regular lights that have a precise location and size, and inverse-square decay.

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