Lights

Lighting Overview

Lighting in Omniverse Kit based apps offers a wide variety of lighting options and capabilities. Here is a quick look at how you can expect to interact with and manage lighting.

Light Sources

Light sources in Kit based apps are made to realistically emulate real-world lights.

Light Types	Real World Equivalent
Distant Light	Direct Sun/Moon light
Sphere Light	Light Bulb
Rect Light	Rectangular Panel Light
Disc Light	Circular Panel Lights and Spotlights
Cylinder Light	Neon/Fluorescent Light Tubes
Dome Light	HDRI Skysphere (Background) lighting

Distant Light

Distant lights are parallel rays of light useful for showering an entire scene in a directional light. Meant to emulate lights infinitely far away, shadows cast with type of light will be hard edged and rather harsh compared to other lights. Ideal for Sun/Moon light, distant lights are generally a critical element to any outdoor scene.

Sphere Light

Sphere lights emit light in all directions from a central ball (not a point). The softness of the shadows (and overall intensity) are dictated by the radius of the central ball. Sphere lights are effective replacements for light bulbs.

Light Specific Properties	Usage
Radius	Source Sphere Radius
Treat as Point	Makes the sphere size infinitely small

Rectangular (Rect) Light

Rectangular lights are capable of emulating light generated from a panel. The rectangle can be adjusted in width and length to accommodate any ratio from thin rectangle to square shape. This affect overall light power and shadow softness.

Light Specific Properties	Usage
Height	Depth of the light source (x value)
Length	Length of the source (y value)

Note

The Texture File functionality is not supported in RTX Real time rendering mode. This will be fixed in a future update.

Disc Light

Similar to the rect light the Disc light emulates panel lighting but in the shape of a circle. Size is controlled by radius which affects overall light power as well as shadow softness. If shaping is used, the light acts as a traditional spotlight and has specialized controls to adjust the shape and color of the lights falloff.

Light Specific Properties	Usage
Radius	Source Disc Radius
Cone Angle	Controls Projection Angle of the light. Higher is wider, lower is narrower.
Cone softness	Increased the value to “soften” the lights cone edges.
Focus	Higher Values soften and blends with Focus Tint
Focus Tint	Tints the edges of the light falloff based on Focus

Note

Increasing Shadow samples per pixels in Rendering Settings smooths light falloff at the cost of render speed.

Cylinder Light

Tubular lighting useful in emulating neon/fluorescent light tubes and other linear omnidirectional lighting.

Light Specific Properties	Usage
Radius	Source Tube Radius
Length	Source Tube Length

Dome Light

Used for image-based (background) lighting when supplied with a texture. Dome lights allow you to easily light your entire scene with a high or low dynamic range image.

Light Specific Properties	Usage
Texture:File	Low/High Dynamic Range image input
Texture:Format	Selects Skydome Format Choices include: LatLong, Angular, Mirrored Ball and Vertical Cross HDR Formats: HDR, Exporter LDR Formats: PNG

Common Light Properties

Common Light Properties	Usage
Color	The color of the light
Color Temperature	The color of the light using the Kelvin Scale.
Diffuse Multiplier	Adjusts the Diffuse Power of the light.
Enable Color Temp	True uses Color Temperature for input, False uses Color.
Exposure	Exposure offers a quick way to increase/decrease light intensity in stops.
Intensity	Base luminosity of the light source.
Normalize Power	Brings light power into a normalized range.
Specular Multiplier	Adjusts the amount specularity the light contributes to.

Light Linking

In Omniverse, Lights can be linked to surfaces allowing individualized response to specified lights.

Note

Light Linking is a specific utility of Path Tracing and only works in PT Mode.

Light linking can be used when very specific control over scene lighting is needed by specifying which lights contribute illumination or shadows to an object.

Property Panel Settings

Under the Light Link and Shadow Link menus for a light, primitives can be included or excluded. The underlying mechanism for these lists are USD collections. The expansion rules control how primitives are included or excluded from these collections. explicitOnly links to one specific primitive, expandPrims includes the children of the specified primitive, and expandPrimsAndProperties includes children and attributes, though attributes are not currently supported in the light linking paradigm. The exclude collation can act as a subtraction boolean against the include list. If the expansion rule is set to expandPrims and the top of a hierarchy is selected as s single selection, then the exclude list can be used to remove lower level objects from the include list.

Light Link

Option	Result
Light Link Include Root	On by default, this includes all objects under the root primitive
Light Link Expansion Rule	explicitOnly, expandPrims, expandPrimsAndProperties
Light Link Includes	Add Target will bring up a menu to select objects to link to the light
Light Link Excludes	Add Target will bring up a menu to select objects to exclude from the light

Shadow Link

Option	Result
Shadow Link Include Root	On by default, this includes all objects under the root primitive
Shadow Link Expansion Rule	explicitOnly, expandPrims, expandPrimsAndProperties
Shadow Link Includes	Add Target will bring up a menu to select objects to link to the light’s shadow
Shadow Link Excludes	Add Target will bring up a menu to select objects to exclude from the light’s shadow