VDAO

vec2 projdir(vec3 start, vec3 end)
{
    vec4 clipspace = (ProjectionMatrix * ViewMatrix) * vec4((start), 1.0);
    vec2 sspace1 = ((clipspace.xyz / clipspace.w).xy + 1.0) / 2.0;
    clipspace = (ProjectionMatrix * ViewMatrix) * vec4((end), 1.0);
    vec2 sspace2 = ((clipspace.xyz / clipspace.w).xy + 1.0) / 2.0;
    return (sspace2 - sspace1);
}

bool testVisibility3d(vec2 cuv, vec3 w1, vec3 w2) 
{
    float d3d1 = length(w1);
    float d3d2 = length(w2);
    vec2 sdir = projdir(FromCameraSpace(w1), FromCameraSpace(w2));
    for(float i=0;i<1.0;i+= 0.1) 
    { 
        vec2 ruv = mix(cuv, cuv + sdir, i);
        vec3 wd = texture(worldPosTex, ruv).rgb; 
        float rd3d = length(wd) + 0.01;
        if(rd3d < mix(d3d1, d3d2, i) && mix(d3d1, d3d2, i) - rd3d < 1.01) 
        {
            return false;
        }
    }
    return true;
}

float rand(vec2 co){
    return fract(sin(dot(co.xy ,vec2(12.9898,78.233))) * 43758.5453);
}

vec3 VDAO() 
{
    vec3 posCenter = texture(worldPosTex, UV).rgb;
    vec3 normalCenter = normalize(texture(normalsTex, UV).rgb);
    vec3 ambient = vec3(0);
    const int samples = 65;

    // choose between noisy and slower, but better looking variant
    //float randomizer = 138.345341 * rand(UV);
    // or faster, non noisy variant, which is also cool looking
    const float randomizer = 138.345341;

    uint counter = 0;
    for(int i=0;i<samples;i++)
    {
        float rd = randomizer * float(i);
        
        vec3 displace = vec3(
        fract(rd) * 2 - 1, 
        fract(rd*12.2562), 
        fract(rd*7.121214) * 2 - 1
        ) * clamp(length(posCenter), 0.1, 2.0);
        
        float dotdiffuse = 1.0 - max(0, dot(normalize(displace),  (normalCenter.xyz)));
        
        for(int div = 0;div < 2; div++)
        {
            if(testVisibility3d(UV, posCenter, posCenter + displace))
            {
                ambient += vec3(1,1,1) * dotdiffuse;
            }
            displace = displace * 0.5;
            counter++;
        }
    }
    vec3 rs = counter == 0 ? vec3(0) : (ambient / (counter));
    return rs;
}