vec4 sampledDiffuse = terrain_text_1_r_color + terrain_text_1_g_color + terrain_text_1_b_color + terrain_text_1_a_color;
    vec4 sampledNormal  = normalize(calcNormal(p3d_Texture0, vOutput.texcoord));
    vec4 sampledSpecular = vec4(0.3, 0.3, 0.3, 0.3);
    vec4 sampledRoughness = vec4(0.0, 0.0, 0.0, 0.0);

    .....

    vec3 normal = sampledNormal.xyz;
    //vec3 tangent_a = cross(normal.xyz, vec3(1.0, 0.0, 0.0));
    //vec3 tangent_b = cross(normal.xyz, vec3(0.0, 0.0, 1.0));
    //vec3 tangent = mix(tangent_a, tangent_b, step(length(tangent_a), length(tangent_b)));
    vec3 tangent = cross(vec3(1.0, 0.0, 0.0), normal);
    vec3 binormal = cross(tangent, normal);