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

#include "stdcycles.h"

shader node_normal_map(float Strength = 1.0,
                       color Color = color(0.5, 0.5, 1.0),
                       string space = "tangent",
                       string attr_name = "geom:tangent",
                       string attr_sign_name = "geom:tangent_sign",
                       output normal Normal = N)
{
  color mcolor = 2.0 * color(Color[0] - 0.5, Color[1] - 0.5, Color[2] - 0.5);
  int is_backfacing = backfacing();

  if (space == "tangent") {
    vector tangent;
    vector ninterp;
    float tangent_sign;
    float is_smooth = 0.0;

    getattribute("geom:is_smooth", is_smooth);
    if (!is_smooth) {
      ninterp = normalize(transform("world", "object", Ng));

      /* the normal is already inverted, which is too soon for the math here */
      if (is_backfacing) {
        ninterp = -ninterp;
      }
    }

    // get _unnormalized_ interpolated normal and tangent
    if (getattribute(attr_name, tangent) && getattribute(attr_sign_name, tangent_sign) &&
        (!is_smooth || getattribute("geom:normal_map_normal", ninterp))) {
      // apply normal map
      vector B = tangent_sign * cross(ninterp, tangent);
      Normal = normalize(mcolor[0] * tangent + mcolor[1] * B + mcolor[2] * ninterp);

      // transform to world space
      Normal = normalize(transform("object", "world", Normal));
    }
    else {
      Normal = normal(0, 0, 0);
    }
  }
  else if (space == "object") {
    Normal = normalize(transform("object", "world", vector(mcolor)));
  }
  else if (space == "world") {
    Normal = normalize(vector(mcolor));
  }
  else if (space == "blender_object") {
    /* strange blender convention */
    mcolor[1] = -mcolor[1];
    mcolor[2] = -mcolor[2];

    Normal = normalize(transform("object", "world", vector(mcolor)));
  }
  else if (space == "blender_world") {
    /* strange blender convention */
    mcolor[1] = -mcolor[1];
    mcolor[2] = -mcolor[2];

    Normal = normalize(vector(mcolor));
  }

  /* invert normal for backfacing polygons */
  if (is_backfacing) {
    Normal = -Normal;
  }

  if (Strength != 1.0)
    Normal = normalize(N + (Normal - N) * max(Strength, 0.0));
}