The point light is an omnidirectional light source - a small sphere emitting light in all directions.
Creating a Point Light
To create a distant light, right-click in the GafferThree's Object table and select Add → Point Light, or press the P
key. A point light appears as a sphere in the Viewer.
A point light in the Gaffer Object Table and in the Viewer.
Positioning a Point Light
The point light's transform can be edited in the Object tab, or interactively in the Viewer.
Adjusting a Point Light Shape Visibility
A point light's light-emitting sphere can be made Visible to Camera in the Object tab.
Controlling the Light from a Point Light
The Object tab allows specifying the Radius of the point light (as is explained in more details below). The Material tab serves to control several light parameters. The effect of these are explained and illustrated in the next sections.
The Object tab of a point light.
The Material tab of a point light.
Point Light Controls
Radius
The radius of the sphere that emits light in all directions. Increasing the Radius will soften the lit region edge and the shadows casted by the spot light.
Visible to Camera
Makes the light source visible to the camera (a.k.a primary rays). Since the point light is rendered as a sphere with the specified Radius, the visible shape will be a sphere. Note that a Radius of 0 might still produce a very tiny visible dot. This option is only available in 3Delight for Katana.
Light Intensity and Color Controls
Color
Defines the light color.
Intensity
Species the light intensity.
Exposure
This is an additional control over the standard light intensity. Exposure is in many cases a preferred control due to its likeness to photography. Final light intensity is thus computed by:
I = intensity * pow(2, exposure)
Decay Rate
Specify the rate at which the light intensity decreases in function of the distance to the light source. The available values are:
No Decay | Light intensity remains constant with respect to distance. |
---|---|
Linear | Light intensity decreases linearly with distance. |
Quadratic | Light intensity decreases proportionally to the square of the distance. This is the physically correct behaviour. |
Cubic | Light intensity decreases proportionally to the cube of the distance. |
Fine Tuning the Light Contribution to the Shading Components
It is sometimes useful to have a fine and direct control on how the light intensity affects various shading components. The following controls allows for that:
Diffuse Contribution
Specifies a multiplier for the light contribution to diffuse shading.
Specular Contribution
Specifies a multiplier for the light contribution to specular shading.
Hair Contribution
Specifies a multiplier for the light contribution to hair shading.
Volume Contribution
Specifies a multiplier for the light contribution to volumetric effects in atmosphere and OpenVDB volumes.