cheaper_smoothstep.glsl

// cheaper smoothstep
// https://forum.unity.com/threads/how-expensive-is-smooth-step-in-shaders-for-mobile.501809/
float cheapstep(float a, float b, float x) {
    // remap the value
    float remap = x * (1.0 / (b - a)) - (a / (b - a));
    // clamp it to 0 and 1, as smoothstep would
    return clamp(0., 1., remap);
}