UE4 - Biasing Material Function

For one of my products, I needed a function that biased a gradient ramp toward a specified value without washing out the entire range. I came up with a solution that works like this:

• Insert gradient ramp, bias setting, and influence control.
• Gradient midpoint figured from bias setting.
• Power node controls gradient midpoint and pinches/expands gradient around bias setting

This expression is purely linear, but does a fantastic job biasing values with controlled influence and without losing range.

The scale on the left shows how different values affect the gradient ramp. While the pixels at the left and right remain black and white, the middle value (set to 0.2 in this example) remains the same, but its influence increases from -1:∞, with -1 resulting in a sharp black/white cut, -1:0 resulting in a pinched gradient, 0 at neutral (bypass), and anything >0 spreading the gradient further.

The bump for this biasing technique is 11 pixel shading instructions.

This has a lot of practical applications from processing or blending colors and textures in materials to more useful technical purposes biasing values. I'm using this to bias values from random number/seed generators to favor one part of the spectrum over another without losing the full range.

The power node/Influence variable is a bit weird to use, as the negative range is particularly aggressive while the positive range progresses slowly and continues forever. It can be more helpful to square the Influence setting for positive values, but squares do not result in negative values at all.