Let's make a camera and have it show on a monitor.

The entity's used are a Pointcamera entity, infocameralink entity, a funcmonitor brush entity, func_button brush entity.

First build your map and a place to build your monitor. Then place the pointcamera and infocamera_link entities around your map in the areas you want shown on monitor.

Point_camera entity in the properties window you will have to name it (example: cam2a), you can also change the FOV(field of view) to different degrees. Under the Flags option check off the " Start Off " box if you have multiple cameras around your map,except for the first camera in the rotation.

Infocameralink entity in the properties window you will have to enter the name of the monitor in the Entity Whose Material Usesrtcam parameter.(example: monitor). Then in the camera name parameter enter the name of the camera (example: cam2a)

Next let's make some buttons to switch the monitor views. Funcbuttons that is. Make a button out of a brush, then hit the "To Entity" button and tie the brush to a funcbutton. Then in the properties window of the func_button go to the Outputs Tab and click on the Add... button at bottom, on My output named click the drop down menu and select OnPressed , Then the Targets entities named select your camera name Camera name.(Example: cam2a). Then the Via this input select Set On And Turn Others Off. Under the Flags tab you can select some other options like Use Activates and Don't Move.

Now you can build your monitor. Make another brush (the brush you want the view of the cameras on) and hit the "To Entity" button and make it a funcmonitor. In the properties window name it the name of your monitor (Example: monitor) Now highlight the brush and place a DevMonitor texture on the face you want the picture on. Use the Texture Application Tool to do this. Browse for texture name by typing key word in filter box. (Filter word: monitor). As you can see below the dev_monitor textures look weird in Hammer, but show up properly in game.

If you have more than one camera, just make additional Pointcamera, infocameralink and funcbutton entities. naming each set of camera entites different. *On a side note , you can not see your self in the monitor view.

Some in game screenshots:

As you can see from the screenshot of dev_monitor textures, there are different types of monitor effects you can get.Apply the textures and compile the map to see the differences.

THANKS TO WWW.IWANNAMAP.COM FOR THIS AWESOME TUTORIAL

EDITED BY HUNTERKILLER

By request here is a link to the entity file.

And here is a link to another similar tutorial with filters to use on the cameras..