Light attributes¶

Modify the light attributes

1. Select the lights you want to modify.
2. Modify the attributes in the Properties view.

Modify the light attributes using the RenderGraph

Like for the scene graph object, you can override the lights attributes using the RenderGraph.

1. Drag'n drop the light you want to modify in the RenderGraph.
2. Add a RenderGraph/LightAttributes node.
3. Make the light flow into the LightAttributes node.
4. Merge those nodes in your RenderGraph.

   

   We use an Union merge here because the PointLight is not flowing in the main flow.

5. Select the LightAttributes node.
6. Modify the attributes in the Properties view.

The lights attributes.

On

Enable/disable the light. Hiding the light or one of its parents disable the light.

On

Type

The shape of the light. This defines the shape of the positional light.

• Point: the light is single point, and casts sharp shadows.
• Square: the light is a square/rectangle.
• Disc: the light is a circle/ellipse.
• Sphere: the light is a sphere.

A positional light with different types : Point, Square, Disc and sphere.

LightType

Category

The light category this light belong to. The categories can be specified in every RenderPass AOVs to select the visible lights in those AOVs.

Category

Light Set

The sets of objects the light illuminates. The objects that belong to any of these sets are illuminated by the light. This attribute is a comma separated list of object sets.

The sphere object in the Lights set and not in the Lights set.

LightSet

Shadow Set

The set of objects that cast shadows in the light. The objects that belong to any of these sets cast shadows in the light. This attribute is a comma separated list of object sets.

The sphere object in the Shadows set and not in the Shadows set.

ShadowSet

Color

The light color.

A sphere light with a color of 5000 K, 6654 K and 8000 K.

You can select a temperature for your light color using the K button in the color picker.

The K button toggle the color picker between the RGB mode and the Kelvin mode.

Color

Dynamic Attributes > Diffuse

Multiply the light color by this color for the diffuse BRDF.

The Diffuse attribute set to white and to blue.

Dynamic Attributes > Specular

Multiply the light color by this color for the specular BRDF.

The Specular attribute set to white and to red.

Shadow Id

The color the shadows for this light in the ShadowMask pass.

ShadowId

Size

The light size. Only for the Square, Disc and Sphere lights.

A sphere light with a size of 0.5, 1.0 and 2.0.

Size

Intensity

Linear control of the light brightness. The total intensity of the light is computed using the formula: Color * Intensity * pow (2, Exponent).

A sphere light with an intensity of 0.5, 1.0 and 2.0.

Intensity

Exponent

Exponential control of the light brightness. The total intensity of the light is computed using the formula: Color * Intensity * pow (2, Exponent).

A sphere light with an exponent of 5, 6 and 7.

Exponent

Primary Use Surface

When enabled, area lights use the surface shader for rendering the primary visibility

A sphere light with Use Primiary set to ON and OFF.

PrimaryUseSurface

Absolute

Control if the global intensity of the light is normalized by the light size. If enabled, the size of the light can be changed freely without modifying its overall brightness.

Absolute

Cast Shadows

Enable/disable the light geometry to cast shadows. When using Square, Disc, Sphere and Mesh lights, it is possible to control if the light as a geometry will cast shadows in other lights/environments. This attributes doesn't enable/disable the shadows casted by the objects from this light. To remove those shadows, set the Light > Shadow Set attribute to an empty string.

CastShadows

Separate Sampling

When active, the light is sampled independently from other lights, resulting in more predictable results at the cost of longer rendering times.

SeparateSampling

Shoot Photons

When active, the light can contribute to bidirectional path tracing, hence reducing noise at the cost of longer rendering times.

UsePortals

This value controls if the light can be clipped by portals.

UsePortals

Decay

Control the attenuation with the distance of the light intensity. The attenuation is computed using the formula: 1 / pow (distance, decay).

A sphere light with a decay of 1, 2 and 3.

Natural lights have a decay of 2. Decreasing this value increases the range of the light, but is not physically accurate. In volumetrics, a light using a decay of 2 generates less noise than using another decay value. See also Library/Lights/SphereLight to use a light with adjustable falloff.

Decay

Ray Length

The length to which the light illuminates. Beyond that distance, objects won't cast shadows. Only for distant lights.

Angle

The angular size of the light, in degrees. Increasing this value will cast softer shadows and make the light brighter, unless Absolute is enabled. Only for distant lights.

Angle

Threshold

Clamp the light energy to this value. Increasing this value may reduce the render time. Increase this attribute if your project includes lot of lights.

Threshold

Light Map

The light illumination map.

LightMap

Gamma

The illumination map gamma correction.

Gamma

Hue

The illumination map hue correction.

Hue

Saturation

The illumination map saturation correction.

Saturation