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.
- 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.
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
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.