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This tutorial was originally created by wisemx. It was originally posted on SDKnuts.net.

In this tutorial, we will approach basic aspects of using lasers in level design.

Moving Laser

Moving laser

The image to the right shows a laser that travels back and forth from both ends of a tunnel, and will kill the player if touched. The height of the tunnel is big enough for the player to be able to jump over the laser. The player can not go under the laser at this height however.

There are several ways to create an effect like this, the settings and methods that is used in this tutorial can easily be changed to your liking. Notice the sprite placed on each side for a burning hot effect.

There's a secondary ambient effect used in this tutorial, not related to the laser: a water puddle was created on the floor, and it will make a splash sound.

An env_beam is used on each side of the tunnel to create the moving laser:

Class: env_beam
Keyvalues Comments
Parent Beam01train Right side parent equals Beam02train
Brightness 75
Beam Color 255 0 0
Life 0 (Infinite)
Width of Beam 0.7
Noise 0
Sprite name sprites/laserbeam.spr
Texture scroll rate 40
Damage 1000
Start Entity Beam01 Beam02 for the right side
Ending Entity Beam02 Beam01 for the right side
Touch Type Not a tripwire
Checkbox-on.png Start

Setup in Hammer

Setup in Hammer

To the right there's a shot from Hammer of the left side env_sprite, env_beam, func_tracktrain and first path_track.

Note.pngNote:The left and right sides are identical except for entity names.

Objects used

  • Transparent = func_tracktrain
  • Purple = env_beam
  • Green = env_sprite
  • Red = path_track

By looking at the image you can see the env_sprite is parented to the env_beam. The env_beam is parented to the invisible func_tracktrain. Our first path_track, the starting point, is nestled right in there with the other entities.


These are the settings for each env_sprite, which are only used for a slight effect.

Class: env_sprite
Keyvalues Comments
Parent Beam01 Beam02 for right side
Render FX Normal
Render Mode Additive
FX Amount 150
FX Color 255 0 0
Disable receiving shadows Yes
Frame rate 10.0
Sprite name materials/sprites/glow03.vmt
Scale 0.2
Size of Glow 2.0
Checkbox-on.png Start


Settings for each func_tracktrain:

Class: func_tracktrain
Keyvalues Comments
Name Beam01train Beam02train for the right side
Disable receiving shadows Yes
Disable Shadows Yes
First Stop Target Beam01path01 Beam02path01 for the right side
Max speed 60
Initial Speed 60
Change Velocity Instantaneously
Change Angles Near path_tracks
Distance between the wheels 10
Height above the track 0
Bank angle on turns 0
Move sound d3_citadel.weapon_zapper_beam_loop1 Left side only
Volume 2
Checkbox-on.png No User Control
Checkbox-on.png Passable
Checkbox-on.png Fixed Orientation
Checkbox-on.png Is unblockable by Player
Setup in Hammer


Notice, in the image to the right, that there are only 4 path_track entities: two on each side, for each func_tracktrain.

On the left side the first path_track references the second path_track which in turn references the first path_track, which causes the lasers on each side to go in a loop, back and forth.

By adding more of these path_track's you could cause the laser to travel in a zigzag pattern. You could also attach multiple lasers to each side, for a double effect as an example. You are free to change the visual effect of the laser, its speed and the tiny sprite to your liking.

Tip.pngTip:The reason an env_beam was used on each side rather than only on one side is that the laser effect appears to be much better. However, you can experiment with this.

Settings for first path_track on the left side:

Class: path_track
Keyvalues Comments
Name Beam01path01 Beam02path01 on the Right side
Name Beam01path02 Beam02path02 on the Right side

Water puddle

Water Puddle

The water puddle effect is done with an info_overlay. One can place an env_cubemap over this, an ambient_generic for the sound and a trigger_multiple to play the sound when the player steps there.

Setup in Hammer


Class: info_overlay
Keyvalues Comments
Material decals/decalborealispuddle001a


Class: ambient_generic
Keyvalues Comments
Name WaterSound
Sound name Water.StepLeft
Volume 4
Checkbox-on.png Start Silent
Checkbox-on.png Is NOT Looped


Class: trigger_multiple
Keyvalues Comments
Start disabled No
Delay before reset 1
Checkbox-on.png Clients
Checkbox-on.png Everything
My output Target entity Target input Parameter Delay Only once Comments
Entity-output-icon.png OnStartTouch WaterSound PlaySound

Laser turning a corner

Laser turning a corner

The trick to making the laser turn a corner is to stop the inside train until the outside train catches up. Take a look at the Outputs for the path_tracks in the corner, should be straight-forward.

The next step is to make the laser teleport to the first path_track so it can start over. To do that just check the flag Teleport to this path_track, in both of the first ones.

The download for this tutorial contains two vmf projects. In the second example the laser turns a corner and travels down another tunnel. Notice that no sprites were used in the second example, since it looked better without them.

See also