/*
 * Copyright 2011-2013 Blender Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License
 */

#include "stdosl.h"

shader node_anisotropic_bsdf(
	color Color = 0.0,
	string distribution = "GGX",
	float Roughness = 0.0,
	float Anisotropy = 0.0,
	float Rotation = 0.0,
	normal Normal = N,
	normal Tangent = normalize(dPdu),
	output closure color BSDF = 0)
{
	/* rotate tangent around normal */
	vector T = Tangent;

	if (Rotation != 0.0)
		T = rotate(T, Rotation * M_2PI, point(0.0, 0.0, 0.0), Normal);

	/* compute roughness */
	float RoughnessU, RoughnessV;
	float aniso = clamp(Anisotropy, -0.99, 0.99);

	if (aniso < 0.0) {
		RoughnessU = Roughness / (1.0 + aniso);
		RoughnessV = Roughness * (1.0 + aniso);
	}
	else {
		RoughnessU = Roughness * (1.0 - aniso);
		RoughnessV = Roughness / (1.0 - aniso);
	}

	if (distribution == "Sharp")
		BSDF = Color * reflection(Normal);
	else if (distribution == "Beckmann")
		BSDF = Color * microfacet_beckmann_aniso(Normal, T, RoughnessU, RoughnessV);
	else if (distribution == "GGX")
		BSDF = Color * microfacet_ggx_aniso(Normal, T, RoughnessU, RoughnessV);
	else
		BSDF = Color * ashikhmin_shirley(Normal, T, RoughnessU, RoughnessV);
}