Smoothstep

Task

Create a gradient effect that smoothly transitions from red to green. The color change should be most noticeable between the x-coordinates of 0.25 and 0.75.

Requirements

The shader should avoid using branching or conditional statements in its code, and instead rely on the smoothstep and mix functions to determine the color of each pixel.

Theory

The smoothstep function is used to perform smooth interpolation between two values based on a third interpolation factor. This function provides a smoother transition compared to linear interpolation by applying a smooth curve to the interpolation process.

Function Signature

smoothInterpolation = smoothstep(edge0, edge1, x)

How It Works

The smoothstep function takes three arguments:

• edge0: The lower threshold value.

• edge1: The upper threshold value.

• x: The interpolation factor.

Calculation details:

1. If x is less than or equal to edge0, the result is 0.

2. If x is greater than or equal to edge1, the result is 1.

3. If x is between edge0 and edge1, the result is smoothly interpolated between 0 and 1 using a Hermite interpolation function.

The Hermite interpolation function used by smoothstep ensures that the transition between 0 and 1 is smooth and continuous, resulting in a visually pleasing effect.

Examples

// result will be a smooth color interpolation between red and blue
vec3 out = mix(color1, color2, smoothstep(0.2, 0.8, factor));

In this example, the out color value is transitioning smoothly from 0.2 to 0.8 based on the factor value:

• When factor is less than 0.2: the smoothstep function evaluates to 0.0, resulting in the output being closer to color1.

• When factor is greater than 0.8: the smoothstep function evaluates to 1.0, resulting in the output being closer to color2.

• When factor is between 0.2 and 0.8: the transition is smooth and continuous, providing more control over where the blending occurs.