You just need to change the following lines as below, then recompile the custom material node.117 float3 IridescenceBRDF(float3 L, float3 V, float3 N, float <b>Thickness</b>, float eta2, float eta3, float kappa3, float alpha) 123 float eta_2 = lerp(1.0, eta2, smoothstep(0.0, 0.03, <b>Thickness</b>)); 149 float OPD =…