   vec3 p2 = from + (s + zoffset) * dir;
            vec3 p3 = from + (s3 + zoffset) * dir;
            p2 = abs(vec3(0.85) - mod(p2, vec3(0.85 * 2.)));
            p3 = abs(vec3(0.85) - mod(p3, vec3(0.85 * 2.)));
            t3 = field(p3);
            float pa, a = pa = 0.;
            for(
                int i = 0;
                i < 8;
                i ++
            )
                {
                    p2 = abs(p2) / dot(p2, p2) - formuparam;
                    float D = abs(length(p2) - pa);
  