Area-based screen tint

Legend has it that, in American films and TV, scenes taking place in Mexico always have a sepia color filter on top of them. Now you can bring the Mexican Filter™ to your own maps!

This example demonstrates three things:

1. How to use env_fade's "Modulate" and "Fade From" flags to create a color overlay (tint) effect on the player's screen
2. How to make the effect stay on for as long as the player remains inside a certain area
3. How to make the transition in and out of the tint smooth(er)

Explanation

The tint effect is achieved by having an env_fade (named screen_tint) repeatedly triggered by a trigger_multiple (mexico) covering the whole area it's supposed to affect.
Both the fade's "Hold Fade" time and the trigger's delay before reset are set to 1 second, so the fade gets re-triggered every second while the player stays inside the trigger.

That would be enough for a continuous tint that fades away when the player leaves the area, but if you also want it to fade in smoothly, it'll need a more complex setup -- especially when the player can move freely between areas like in this example.

For the smooth transition, I added these to the setup:
- A second env_fade (screen_tint_start) with the "Fade From" flag disabled
- A second trigger_multiple (mexico_border) at the threshold between areas with a 0.5 second delay before trigger
- Four trigger_changetarget, one pair named change1 and another pair named change2

When the player crosses the border, this is what happens:
- The threshold's trigger_multiple (mexico_border) targets the pair of trigger_changetarget called change1 after a delay of 0.5s
- Meanwhile, the area's trigger_multiple, mexico, targets screen_tint_start, since that is its initial target
- The change1 pair activates, making it so mexico now targets screen_tint every second from now on, and mexico_border now targets the change2 pair

If the player walks back through the border, mexico_border will now trigger the change2 pair, which reset both mexico and mexico_border to their initial targets so this whole sequence can be repeated.

Usage suggestions

• A room that fills up with toxic gas, that the player has to escape from
• A portal that shades the player's vision greener and greener as they approach
• A blue flash inside the player's eye near a strong source of radiation
• Simulating a "psychic attack", like that scene with the Advisor in Half-Life 2: Episode 1
• Recreating your favorite episode of Breaking Bad

Notes

• Going in and back out through the threshold too quickly will break the effect; find a way to slow the player down, or don't let them back out the way they came in
• Probably there are better/simpler ways of achieving this effect, so experiment!

Updates

• 2025/02/18: Improved readme and Vault description slightly

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Lastly, I'd like to thank you fine people of TWHL, I wouldn't have learned so much about mapping without the resources and information available here. You guys rock!

-- Mota