/* SPDX-License-Identifier: Apache-2.0
 * Copyright 2011-2022 Blender Foundation */

#include "stdcycles.h"

shader node_hair_bsdf(color Color = 0.8,
                      string component = "reflection",
                      float Offset = 0.0,
                      float RoughnessU = 0.1,
                      float RoughnessV = 1.0,
                      normal Tangent = normal(0, 0, 0),
                      output closure color BSDF = 0)
{
  float roughnessh = clamp(RoughnessU, 0.001, 1.0);
  float roughnessv = clamp(RoughnessV, 0.001, 1.0);
  float offset = -Offset;

  normal T;
  float IsCurve = 0;
  getattribute("geom:is_curve", IsCurve);

  if (isconnected(Tangent)) {
    T = Tangent;
  }
  else if (!IsCurve) {
    T = normalize(dPdv);
    offset = 0.0;
  }
  else {
    T = normalize(dPdu);
  }

  if (backfacing() && IsCurve) {
    BSDF = transparent();
  }
  else {
    if (component == "reflection")
      BSDF = Color * hair_reflection(Ng, roughnessh, roughnessv, T, offset);
    else
      BSDF = Color * hair_transmission(Ng, roughnessh, roughnessv, T, offset);
  }
}