LYGIA Shader Library

Use:

blendScreen(<float|vec3> base, <float|vec3> blend [, <float> opacity])

Check it on Github

#ifndef FNC_BLENDSCREEN
#define FNC_BLENDSCREEN
float blendScreen(in float base, in float blend) {
    return 1. - ((1. - base) * (1. - blend));
}

vec3 blendScreen(in vec3 base, in vec3 blend) {
    return vec3(blendScreen(base.r, blend.r),
                blendScreen(base.g, blend.g),
                blendScreen(base.b, blend.b));
}

vec3 blendScreen(in vec3 base, in vec3 blend, float opacity) {
    return (blendScreen(base, blend) * opacity + base * (1. - opacity));
}
#endif

Use:

blendScreen(<float|float3> base, <float|float3> blend [, <float> opacity])

Check it on Github

#ifndef FNC_BLENDSCREEN
#define FNC_BLENDSCREEN
float blendScreen(in float base, in float blend) {
    return 1. - ((1. - base) * (1. - blend));
}

float3 blendScreen(in float3 base, in float3 blend) {
    return float3(  blendScreen(base.r, blend.r),
                    blendScreen(base.g, blend.g),
                    blendScreen(base.b, blend.b) );
}

float3 blendScreen(in float3 base, in float3 blend, float opacity) {
    return (blendScreen(base, blend) * opacity + base * (1. - opacity));
}
#endif