Spot Light Controls

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). This option is only available in 3Delight for Katana.

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. 

Spread

Specifies how much the light is focused towards the center of the spot light. Large values spread the light more evenly, while smaller values concentrates the light towards the center, making the center brighter. This is similar to focusing a light beam with a lens or a magnifying glass.