Creating a Spot Light

An area light source can be created in the GafferThree node parameters panel...

A spot light in the GafferThree node parameters and in the Viewer.

Controlling a Spot Light

The object tab serves to select the Spot Radius of the spot light and wether it is Visible to Camera. It also presents the light's transform (which can be edited interactively in the Viewer). The Material tab serves to control several parameters of the spot light. The effect of these are explained and illustrated in the next section.

Spot Radius

The radius of the circle that emits light. If the spot light is seen as a cone, this is analogue to truncating the cone tip where the cone has a radius equal to Spot Radius. A very small value makes the cone near ideal. Increasing the Spot 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). 

enable aim constraint

Turning this parameter on will display the standard GafferThree parameters for aim constraint.

Cone Angle

Defines the cone angle, in degrees. 

Penumbra Angle

Defines the spread of the zone over the spot light beam edge where the light intensity will linearly falloff to 0. A value of 0 defines a sharp spot light beam edge. Positive angles define a beam falloff zone that spreads larger than the cone angle; larger values making a softer edge. Negative values define a falloff zone smaller than the cone angle; again, larger values making a softer beam edge.

Drop Off

Specifies the rate at which the light intensity decreases from the spot light beam center to the edge.