LYGIA Shader Library

Use:

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

Check it on Github

#ifndef FNC_BLENDSUBTRACT
#define FNC_BLENDSUBTRACT
float blendSubtract(in float base, in float blend) {
    return max(base + blend - 1., 0.);
}

vec3 blendSubtract(in vec3 base, in vec3 blend) {
    return max(base + blend - vec3(1.), vec3(0.));
}

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

Use:

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

Check it on Github

#ifndef FNC_BLENDSUBTRACT
#define FNC_BLENDSUBTRACT
float blendSubtract(in float base, in float blend) {
    return max(base + blend - 1., 0.);
}

float3 blendSubtract(in float3 base, in float3 blend) {
    return max(base + blend - float3(1., 1., 1.), float3(0., 0., 0.));
}

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