Spectron is a procedural lighting system that lets you create procedurally-driven volumetric lighting - like spotlights - with blockers, barn doors, gels (in the Distribution pin) and more.  Spectron is exposed as a Procedural light node type, which you can use for quick volumetric effects and spotlight generation (Figure 1). The Spotlight parameters can be access from the Shader editor (Figure 2) or the Light Properties Panel (Figure 3). 

Figure 1: The Volumetric Spotlight and it's assocated parameters


Figure 2: The Volumetric spolight Parameters in the Shader Editor


Figure 3: The Volumetric spolight Parameters in the Light Properties panel

Parameters

Accessible - Shader Editor and Light Properties

Volumetric Spotlight

      • Cone Width Source type - Automatic calculate the cone width from the shape in the OpenGL viewport.
      • Throw Distance - The distance from the origin of the light source that the volumetric light will reach.
      • Cone Width - The width of the volumetric light's cone.
      • Cone Hardness - Determines the softness/hardness of the light cone's edge.
      • Light Medium - Defines the type of medium the light will pass through. 
      • Emitter Material - Defines the material of the light source. 
      • Barn Doors Material:  Defines the material of the Barn Door geometry.

Barn Doors

      • Enable Barn Doors - Enables or disables the barn door feature.
      • Barn Door Size - Determines the size of the barn doors.
      • Barn Door 1-4 Angle - Determines the angle for each of the four barn doors.