for (int i = 0; i < numActiveLights; ++i)
    {
        vec3 lightPos = lights[i].position.xyz;
        float lightType = lights[i].position.w;

        vec3 L = normalize(lightPos - FragPos_world);
        vec3 H = normalize(V + L);
        float distance = length(lightPos - FragPos_world);
        float NdotL = max(dot(N, L), 0.0);
        vec3 radiance = lights[i].color.rgb * lights[i].color.a;
        float attenuation = 0.0;
        float shadow = 0.0;
        if (lightType == 0)
        {
            float radius = lights[i].params1.x;
            float radiusFalloff = pow(1.0 - clamp(distance / radius, 0.0, 1.0), 2.0);
            attenuation = radiusFalloff / (distance * distance + 1.0);
            if(attenuation > 0.0 && (lights[i].shadowMapHandle.x > 0 || lights[i].shadowMapHandle.y > 0) ) shadow = calculatePointShadow(lights[i].shadowMapHandle, FragPos_world, lightPos, lights[i].params2.x, lights[i].params2.y);
        }
        else
        {
            float lightCutOff = lights[i].params1.y;
            float lightOuterCutOff = lights[i].params1.z;
            vec3 lightDir = lights[i].direction.xyz;

            float theta = dot(L, -lightDir);
            if (theta > lightOuterCutOff) {
               float epsilon = lightCutOff - lightOuterCutOff;
               float cone_intensity = clamp((theta - lightOuterCutOff) / epsilon, 0.0, 1.0);
               float radius = lights[i].params1.x;
               float radiusFalloff = pow(1.0 - clamp(distance / radius, 0.0, 1.0), 2.0);
               attenuation = cone_intensity * radiusFalloff / (distance * distance + 1.0);
               float cookie_attenuation = 1.0;
               if (attenuation > 0.0 && (lights[i].shadowMapHandle.x > 0 || lights[i].shadowMapHandle.y > 0)) {
                   float angle_rad = acos(clamp(lightCutOff, -1.0, 1.0));
                   if (angle_rad < 0.01) angle_rad = 0.01;
                   mat4 lightProjection = perspective(angle_rad * 2.0, 1.0, 1.0, lights[i].params2.x);
                   vec3 up_vector = vec3(0,1,0);
                   if (abs(dot(lightDir, up_vector)) > 0.99) up_vector = vec3(1,0,0);
                   mat4 lightView = lookAt(lightPos, lightPos + lightDir, up_vector);
                   mat4 lightSpaceMatrix = lightProjection * lightView;
                   vec4 fragPosLightSpace = lightSpaceMatrix * vec4(FragPos_world, 1.0);
                    if (lights[i].cookieMapHandle[0] > 0u || lights[i].cookieMapHandle[1] > 0u) {
                       vec3 projCoords = fragPosLightSpace.xyz / fragPosLightSpace.w;
                       projCoords = projCoords * 0.5 + 0.5;
                       if (projCoords.x >= 0.0 && projCoords.x <= 1.0 && projCoords.y >= 0.0 && projCoords.y <= 1.0) {
                           sampler2D cookieSampler = sampler2D(lights[i].cookieMapHandle);
                           cookie_attenuation = texture(cookieSampler, projCoords.xy).r;
                       } else {
                           cookie_attenuation = 0.0;
                       }
                   }
                   shadow = calculateSpotShadow(lights[i].shadowMapHandle, fragPosLightSpace, N, L, lights[i].params2.y);
               }
               attenuation *= cookie_attenuation;
            }
        }
        if(attenuation > 0.0) {
            float NDF = DistributionGGX(N, H, roughness);
            float G   = GeometrySmith(N, V, L, roughness);
            vec3  F   = fresnelSchlick(max(dot(H, V), 0.0), F0);
            vec3 kS = F;
            vec3 kD = vec3(1.0) - kS;
            kD *= 1.0 - metallic;
            vec3 numerator    = NDF * G * F;
            float denominator = 4.0 * max(dot(N, V), 0.0) * NdotL + 0.001;
            vec3 specular     = numerator / denominator;
            vec3 diffuseContrib = (kD * albedo / PI) * radiance * NdotL * attenuation * (1.0 - shadow);
            totalDirectDiffuse += diffuseContrib;
            Lo += (diffuseContrib + specular * radiance * NdotL * attenuation * (1.0 - shadow));
        }
    }