Apply barn doors (shutters) to a beam of light

Apply barn doors when you want to create the effect of light pouring out of a half-opened door. Barn Doors are shutters applied to a spot light’s beam. Barn Doors are off by default; you must turn them on, then adjust them to get the desired light spill.

To use Barn Doors

1. Select a Spot Light whose manipulators are displayed, then turn Barn Doors on in the Attribute Editor.
2. In the Light Effectssection of the spot light’s Attribute Editor, turn on Barn Doors.
3. Select Look Through Selected from the view’s Panels menu to look through the selected light. (The Barn Doors manipulators are only visible in the light’s view.)

   Four blue lines appear. These lines represent a rectangular boundary for the spot light. No light reaches the regions outside the blue line-boundaries.

   
4. You can directly manipulate each of the four lines with the Move tool to shift the boundaries. (Alternatively, you can enter precise numerical values in the Attribute Editor.)

   Attributes are in degrees measured from the spot light to the blue line-boundary. For instance, for an 80 degree spot light, the four blue line-boundaries are 40 if the boundaries lie exactly at the spot light border.

   When you use the Barn Doors settings, the Light Shape sample changes at the top of the Attribute Editor.

   
5. Tweaking the penumbra value displays a second circle. Change the value in the Attribute Editor or click the Index Manipulator icon to display and use the manipulator, then select Panels > Look Through Selected to see the circle.

   The region between the two circles results in a softer illumination.

   
6. If the penumbra value is set to 0 (the default) and Barn Doors is on, this results in a very hard-edged look to the lighting. With a non-zero penumbra value, the barn door effect is a smooth illumination of the scene.

   You can also verify the illumination by looking at the Light Shape and Intensity Sample at the top of a spot light’s Attribute Editor. These change as you change the values for the spot light.

   
7. To return to the current view, select the view from the Panel menu.