Final Oren-Nayar diffuse with Fresnel approximaton from research.tri-ace.com (0) in HLSL.

   //////////////////////////////////////////////////
	// a = roughness				//
	// f0 = fresnel   				//
	// LdN = dot( light_direction, surface_normal ) //
	// VdN = dot( view_direction, surface_normal )  //
	// LdV = dot( light_direction, view_direction ) //
	//////////////////////////////////////////////////
	float fTheta = f0+dot((1.0f-f0), pow(2.0f, -9.60232*pow(VdH,8.0f)-8.58092*VdH));
	float Bp = 0.0f;
	float Bpl = LdV-(VdN*LdN);	
	float Fr = (1.0f-(0.542026f*(a*a)+0.303573f*a)/((a*a)+1.36053f))*
		(1.0f-(pow(1.0f-VdN,5.0f-4.0f*(a*a)))/((a*a)+1.36053f))*
		((-0.733996*(a*a*a)+1.50912*(a*a)-1.16402*a)*(pow(1.0f-VdN,1.0f+(1.0f/(39.0f*(a*a*a*a)+1.0f))))+1.0f);
	float Lm = (max(1.0f-(2.0f*a),0.0f)*(1.0f-(1.0f-pow(LdN,5.0f)))+min(2.0f*a,1.0f))*((1.0f-0.5f*a)*LdN+(0.5*a)*(pow(LdN,2.0f)));
	float Vd = ((a*a)/(((a*a)+0.09f)*(1.31072f+0.995584f*VdN)))*(1.0f-(pow(1.0f-LdN,(1.0f-0.3726732*(VdN*VdN))/(0.188566f+0.38841*VdN))));
	if (Bpl < 0.0f)
		Bp = 1.4f*VdN*LdN*(LdV-(VdN*LdN));
	else 
		Bp = LdV-((VdN*LdN));
	float aDiffuse = (21.0f/(20.0f*pi))*(1.0f-f0)*((Fr*Lm)+(Vd*Bp));