Lightning

This is a tutorial for adding a lightning storm to a map.

It is assumed that the reader knows how to create a 3D skybox before reading this tutorial.

Custom lightning sprites

Custom made lightning sprites.

Here are all the sprites of (normal) lightning bolts in the HL2 SDK:

• bluelight1.vmt
• lgtning.vmt
• lgtning_noz.vmt
• physcannon_bluelight1b.vmt

You can also download some custom made lightning sprites (seen in the screenshot to the right, but not required for this tutorial). Just create a new sprites folder in the hl2/materials/ folder, unpack the custom sprite files into it, and refresh the SDK content, before running the example map.

Setting up

1. Unless lightning is intended to be close enough to strike within the playing area, create the 3D skybox that will house the lightning storm. Make sure that its fog is disabled.

2. Create two env_sprites and place them next to each other.

3. Select the one of these sprite entities, and open it's properties. This sprite will be the actual lighting bolt. This tutorial example will set the values as follows:

Class: env_sprite
Keyvalues		Comments
Name	lightning1	The name of the lightning sprite.
Render FX	Faster Strobe
Render Mode	Additive
FX Amount (0-255)	200
Sprite Name	sprites/lgtning.vmt	The sprite to use for the lightning. (Don't forget to add ".vmt".)
Scale	2

4. Open the properties of the other sprite. This sprite will be the background glow of the lightning, so that it will light up the sky. This tutorial example will set the values as follows:

Class: env_sprite
Keyvalues		Comments
Name	lightning1glow	The name of the glow sprite.
Render FX	Faster Strobe
Render Mode	Additive
FX Amount (0-255)	25
Sprite Name	sprites/light_glow02.vmt	The sprite to use for the lightning glow. (Don't forget to add ".vmt".)
Scale	7

5. To add some thunder sounds it is recommended to use a soundscape (which is not covered by this tutorial), but a quicker way is to place an ambient_generic entity somewhere in the map in the direction of the lightning strike (Do not place it in the skybox.) and change its properties as follows:

Class: ambient_generic
Keyvalues		Comments
Name	thunder1	The name of the thunder.
Sound Name	k_lab.teleport_post_thunder	You can find four more good thunder sounds if you search for thunder in the sound browser.

Timing it

1. Place a logic_timer in the map, preferably somewhere near your sprites. Open its properties and make the following alterations:

Class: logic_timer
Keyvalues		Comments
Name	lightning1timer	The name of the timer.
Use Random Time	Yes	The lightning will strike at random intervals.
Min Random Interval	5	Minimum time between strikes. Set it lower than this and the thunder will cut itself.
Max Random Interval	60	Maximum time between strikes.

2. Click on the Outputs tab and create the follow outputs:

		My output	Target entity	Target input	Parameter	Delay	Only once	Comments
		OnTimer	lightning1glow	ShowSprite		0.00	No
		OnTimer	lightning1	ShowSprite		0.00	No
		OnTimer	lightning1glow	HideSprite		0.50	No
		OnTimer	lightning1	HideSprite		0.50	No
		OnTimer	thunder1	PlaySound		<delay>	No	<delay> is a value reflecting how far away the lightning struck.

3. Save it and test the map.

4. So far only one lightning bolt has been created. To create more of them, simply place a number of copies of this created set around in the skybox, and name them in sequential order (lightning2, lightning3, lightning4, and so on).

Randomized lightning

To prevent the lightning from unrealistically striking at the same spot over and over again, you can also make the sprites rotate around the skybox. (The lightning will fortunately strike so fast that its movement while visible will barely be noticeable.)

1. Create a small brush textured with the invisible tool texture, turn it into a func_rotating entity, and change its properties as follows:

Class: func_rotating
Keyvalues		Comments
Name	lightningrotator	The name of the rotator.
max rotating speed	3

Also set the following flag:

	Flag
		Start ON

2. Go back to your two sprites and set their Parent field:

Class: env_sprite
Keyvalues		Comments
Parent	lightningrotator	The name of the rotator.

3. You could make another rotator within the actual map, to match the direction of the thunder with the lightning flashes, but using a single stationary ambient_generic for all the bolts won't make that much of a difference.

Just open the ambient_generic entity and set the following flag:

	Flag
		Play everywhere

4. Save and test the map.

See also

• Skybox