9. How to create a pencil of light

First, you have to create a solid brush that will represent the pencil of light. Switch to Template Mode.

In the Template control panel, choose a Solid cube, then add it to the world and texture it as shown below.

Switch to Select Mode,

Select the new brush and open the BrushAttributes dialog box.

Set the brush as an Empty type brush like this:

Now, go to Shear mode:

and in the Side View, deform the brush as shown below:

Get back to the normal Select Mode,

switch to Face mode (by pressing the PageDown key) and open the Face Attributes dialog box.

Set the Transparency of the Empty Brush to 50:

The texture and light are far from perfect in this example, but you get the basic idea. with a nice texture and a few lights well placed you will be able to give the perfect illusion of a pencil of light. Try to use a Cone brush combined with a Light entity and a Corona entity. Following the same principle of the Empty type brush for the Cone, you can easily give the illusion of a projector casting a pencil of light.
Don't forget to place a light entity where the pencil of light hit a surface, like the floor.

Here the result of our pencil of light casting through the window of the corridor after the second room: