SSAO¶

uniform float u_ssaoRadius;
uniform float u_ssaoIntense;
uniform float u_ssaoLOD;

vec2 ssaoSampling( sampler2D depth, vec2 uv0, float theta, vec2 r, float lod, float e ) {
    float ao = 0.;
    float w = 0.;

    vec2 sampleuv = uv0 + vec2(cos(theta), sin(theta)) * r;
    float us_ = texture( depth, sampleuv ).z;
    if (us_ + 0.1 * e < us2 && us2 - us_ < e) {
        ao = smoothstep(0., e, textureLod( depth, sampleuv, lod ).z - us2 );
        w++;
    }

    sampleuv = uv0 + vec2(cos(theta + Pi2_3), sin( theta + Pi2_3)) * r;
    us_ = texture( depth, sampleuv ).z;
    if (us_ + 0.1 * e < us2 && us2 - us_ < e) {
        ao = smoothstep(0., e, textureLod( depth, sampleuv, lod ).z - us2 );
        w++;
    }

    sampleuv = uv0 + vec2(cos(theta - Pi2_3), sin( theta - Pi2_3)) * r;
    us_ = texture( depth, sampleuv ).z;
    if (us_ + 0.1 * e < us2 && us2 - us_ < e) {
        ao = smoothstep(0., e, textureLod( depth, sampleuv, lod ).z - us2 );
        w++;
    }
    return vec2(ao, w);
}

float ssao(sampler2D tex, vec2 uv) {
    float epsilon = 0.01 * max(0.0001, 1. - us2 * us2);
    float lod = u_ssaoLOD;
    vec2 r = u_ssaoRadius / u_texsize / max(0.03, us2);
    float us = 0.;
    float w  = 0.;
    float us_ = texture( tex, uv, lod ).z;
    if (us_ + 0.1 * epsilon < us2 && us2 - us_ < epsilon) {
        vec2 aov2;
        for (int i = 0; i < 5; i++) {
            float d = float(i) / 5. * Pi2_3;
            aov2 += ssaoSampling( tex, uv, d, r, lod * 0.1, epsilon );
        }
        return max(us2 - aov2.x/15., 0.) * u_ssaoIntense;
    }

    return 0.;
}