Fading Values

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This article describes an advanced effect in the Source engine, used to fade fog between different values, but it can be used for any entity that has a color value to change over time. You might also use that article to shift the Z-plane on a map to reduce the visibility, etc.

This trick is quite powerful, as it allows you to alter values that we usually leave static on a map: it would add game immersion.

Entities required

  • logic_relay is perfect to change game values or to abstract the routine. It also makes it much easier to duplicate the effect in other maps.
  • logic_timer is the basis of the effect, this entities is designed for measuring the time ticks.
  • math_counter keeps track of the evolution of the values uppon time for our effect.
  • math_colorblend or math_remap do essentially the same thing: they remap a value based on the input value.

Entity setup

logic_relay
targetname fade_value1
OnTrigger counter SetValue 0
OnTrigger timer 
OnTrigger timer Enable
logic_timer
targetname timer
RefireTime .2
StartDisabled 1
OnTimer counter Add .01
math_counter
targetname counter
max 1
OnHitMax timer Disable
OutValue colorblend InValue
math_colorblend
targetname colorblend
colormin "0 0 0"
colormax "255 255 255"
OutColor env_fog_controller SetColor

Process description

You trigger the logic_relay with another entity, or from the console with ent_fire fade_value1 trigger. This will start the sequence. The logic_relay starts the logic_timer and resets the math_counter. The logic_timer re-fires every .2 seconds, firing its output OnTimer, which adds .01 to the math_counter's stored value. The math_counter outputs its OutValue whenever its value is changed, which is in turn put into the math_colorblend. The math_colorblend takes the input value, which is a range from 0-1, and changes the colors based on that.

This range allows for 100 steps. The values that are setup are a compromise between making the blend really smooth and performance. It's slightly "steppy" because it happens only 5 times a second. It would be a lot smoother if you increased it to happen more often, with less of a step. You could do that by only adding .005 or a smaller value than the default .01.

Once the math_counter hits its maximum value (1) it will fire an output telling the logic_timer to disable. This effectively stops the sequence until the logic_relay is fired again.

OutColor and OutValue outputs both accept a parameter in Hammer, but make sure you do not specify one. The parameter they pass will be dynamically generated by the entity itself.

You can change OutColor on the math_colorblend to target any entity that will accept a color value, and it should work just the same. This entity rig can be further adapted to work with a math_remap, and used to fade between any two values, allowing you to affect the values of pretty much any entity in the game, and change them over time.