/*
 * 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.
 */

/* Triangle Primitive
 *
 * Basic triangle with 3 vertices is used to represent mesh surfaces. For BVH
 * ray intersection we use a precomputed triangle storage to accelerate
 * intersection at the cost of more memory usage */

CCL_NAMESPACE_BEGIN

/* normal on triangle  */
ccl_device_inline float3 triangle_normal(KernelGlobals *kg, ShaderData *sd)
{
  /* load triangle vertices */
  const uint4 tri_vindex = kernel_tex_fetch(__tri_vindex, sd->prim);
  const float3 v0 = float4_to_float3(kernel_tex_fetch(__prim_tri_verts, tri_vindex.w + 0));
  const float3 v1 = float4_to_float3(kernel_tex_fetch(__prim_tri_verts, tri_vindex.w + 1));
  const float3 v2 = float4_to_float3(kernel_tex_fetch(__prim_tri_verts, tri_vindex.w + 2));

  /* return normal */
  if (sd->object_flag & SD_OBJECT_NEGATIVE_SCALE_APPLIED) {
    return normalize(cross(v2 - v0, v1 - v0));
  }
  else {
    return normalize(cross(v1 - v0, v2 - v0));
  }
}

/* point and normal on triangle  */
ccl_device_inline void triangle_point_normal(
    KernelGlobals *kg, int object, int prim, float u, float v, float3 *P, float3 *Ng, int *shader)
{
  /* load triangle vertices */
  const uint4 tri_vindex = kernel_tex_fetch(__tri_vindex, prim);
  float3 v0 = float4_to_float3(kernel_tex_fetch(__prim_tri_verts, tri_vindex.w + 0));
  float3 v1 = float4_to_float3(kernel_tex_fetch(__prim_tri_verts, tri_vindex.w + 1));
  float3 v2 = float4_to_float3(kernel_tex_fetch(__prim_tri_verts, tri_vindex.w + 2));
  /* compute point */
  float t = 1.0f - u - v;
  *P = (u * v0 + v * v1 + t * v2);
  /* get object flags */
  int object_flag = kernel_tex_fetch(__object_flag, object);
  /* compute normal */
  if (object_flag & SD_OBJECT_NEGATIVE_SCALE_APPLIED) {
    *Ng = normalize(cross(v2 - v0, v1 - v0));
  }
  else {
    *Ng = normalize(cross(v1 - v0, v2 - v0));
  }
  /* shader`*/
  *shader = kernel_tex_fetch(__tri_shader, prim);
}

/* Triangle vertex locations */

ccl_device_inline void triangle_vertices(KernelGlobals *kg, int prim, float3 P[3])
{
  const uint4 tri_vindex = kernel_tex_fetch(__tri_vindex, prim);
  P[0] = float4_to_float3(kernel_tex_fetch(__prim_tri_verts, tri_vindex.w + 0));
  P[1] = float4_to_float3(kernel_tex_fetch(__prim_tri_verts, tri_vindex.w + 1));
  P[2] = float4_to_float3(kernel_tex_fetch(__prim_tri_verts, tri_vindex.w + 2));
}

/* Interpolate smooth vertex normal from vertices */

ccl_device_inline float3
triangle_smooth_normal(KernelGlobals *kg, float3 Ng, int prim, float u, float v)
{
  /* load triangle vertices */
  const uint4 tri_vindex = kernel_tex_fetch(__tri_vindex, prim);
  float3 n0 = float4_to_float3(kernel_tex_fetch(__tri_vnormal, tri_vindex.x));
  float3 n1 = float4_to_float3(kernel_tex_fetch(__tri_vnormal, tri_vindex.y));
  float3 n2 = float4_to_float3(kernel_tex_fetch(__tri_vnormal, tri_vindex.z));

  float3 N = safe_normalize((1.0f - u - v) * n2 + u * n0 + v * n1);

  return is_zero(N) ? Ng : N;
}

/* Ray differentials on triangle */

ccl_device_inline void triangle_dPdudv(KernelGlobals *kg,
                                       int prim,
                                       ccl_addr_space float3 *dPdu,
                                       ccl_addr_space float3 *dPdv)
{
  /* fetch triangle vertex coordinates */
  const uint4 tri_vindex = kernel_tex_fetch(__tri_vindex, prim);
  const float3 p0 = float4_to_float3(kernel_tex_fetch(__prim_tri_verts, tri_vindex.w + 0));
  const float3 p1 = float4_to_float3(kernel_tex_fetch(__prim_tri_verts, tri_vindex.w + 1));
  const float3 p2 = float4_to_float3(kernel_tex_fetch(__prim_tri_verts, tri_vindex.w + 2));

  /* compute derivatives of P w.r.t. uv */
  *dPdu = (p0 - p2);
  *dPdv = (p1 - p2);
}

/* Reading attributes on various triangle elements */

ccl_device float triangle_attribute_float(
    KernelGlobals *kg, const ShaderData *sd, const AttributeDescriptor desc, float *dx, float *dy)
{
  if (desc.element == ATTR_ELEMENT_FACE) {
    if (dx)
      *dx = 0.0f;
    if (dy)
      *dy = 0.0f;

    return kernel_tex_fetch(__attributes_float, desc.offset + sd->prim);
  }
  else if (desc.element == ATTR_ELEMENT_VERTEX || desc.element == ATTR_ELEMENT_VERTEX_MOTION) {
    uint4 tri_vindex = kernel_tex_fetch(__tri_vindex, sd->prim);

    float f0 = kernel_tex_fetch(__attributes_float, desc.offset + tri_vindex.x);
    float f1 = kernel_tex_fetch(__attributes_float, desc.offset + tri_vindex.y);
    float f2 = kernel_tex_fetch(__attributes_float, desc.offset + tri_vindex.z);

#ifdef __RAY_DIFFERENTIALS__
    if (dx)
      *dx = sd->du.dx * f0 + sd->dv.dx * f1 - (sd->du.dx + sd->dv.dx) * f2;
    if (dy)
      *dy = sd->du.dy * f0 + sd->dv.dy * f1 - (sd->du.dy + sd->dv.dy) * f2;
#endif

    return sd->u * f0 + sd->v * f1 + (1.0f - sd->u - sd->v) * f2;
  }
  else if (desc.element == ATTR_ELEMENT_CORNER) {
    int tri = desc.offset + sd->prim * 3;
    float f0 = kernel_tex_fetch(__attributes_float, tri + 0);
    float f1 = kernel_tex_fetch(__attributes_float, tri + 1);
    float f2 = kernel_tex_fetch(__attributes_float, tri + 2);

#ifdef __RAY_DIFFERENTIALS__
    if (dx)
      *dx = sd->du.dx * f0 + sd->dv.dx * f1 - (sd->du.dx + sd->dv.dx) * f2;
    if (dy)
      *dy = sd->du.dy * f0 + sd->dv.dy * f1 - (sd->du.dy + sd->dv.dy) * f2;
#endif

    return sd->u * f0 + sd->v * f1 + (1.0f - sd->u - sd->v) * f2;
  }
  else {
    if (dx)
      *dx = 0.0f;
    if (dy)
      *dy = 0.0f;

    return 0.0f;
  }
}

ccl_device float2 triangle_attribute_float2(KernelGlobals *kg,
                                            const ShaderData *sd,
                                            const AttributeDescriptor desc,
                                            float2 *dx,
                                            float2 *dy)
{
  if (desc.element == ATTR_ELEMENT_FACE) {
    if (dx)
      *dx = make_float2(0.0f, 0.0f);
    if (dy)
      *dy = make_float2(0.0f, 0.0f);

    return kernel_tex_fetch(__attributes_float2, desc.offset + sd->prim);
  }
  else if (desc.element == ATTR_ELEMENT_VERTEX || desc.element == ATTR_ELEMENT_VERTEX_MOTION) {
    uint4 tri_vindex = kernel_tex_fetch(__tri_vindex, sd->prim);

    float2 f0 = kernel_tex_fetch(__attributes_float2, desc.offset + tri_vindex.x);
    float2 f1 = kernel_tex_fetch(__attributes_float2, desc.offset + tri_vindex.y);
    float2 f2 = kernel_tex_fetch(__attributes_float2, desc.offset + tri_vindex.z);

#ifdef __RAY_DIFFERENTIALS__
    if (dx)
      *dx = sd->du.dx * f0 + sd->dv.dx * f1 - (sd->du.dx + sd->dv.dx) * f2;
    if (dy)
      *dy = sd->du.dy * f0 + sd->dv.dy * f1 - (sd->du.dy + sd->dv.dy) * f2;
#endif

    return sd->u * f0 + sd->v * f1 + (1.0f - sd->u - sd->v) * f2;
  }
  else if (desc.element == ATTR_ELEMENT_CORNER) {
    int tri = desc.offset + sd->prim * 3;
    float2 f0, f1, f2;

    if (desc.element == ATTR_ELEMENT_CORNER) {
      f0 = kernel_tex_fetch(__attributes_float2, tri + 0);
      f1 = kernel_tex_fetch(__attributes_float2, tri + 1);
      f2 = kernel_tex_fetch(__attributes_float2, tri + 2);
    }

#ifdef __RAY_DIFFERENTIALS__
    if (dx)
      *dx = sd->du.dx * f0 + sd->dv.dx * f1 - (sd->du.dx + sd->dv.dx) * f2;
    if (dy)
      *dy = sd->du.dy * f0 + sd->dv.dy * f1 - (sd->du.dy + sd->dv.dy) * f2;
#endif

    return sd->u * f0 + sd->v * f1 + (1.0f - sd->u - sd->v) * f2;
  }
  else {
    if (dx)
      *dx = make_float2(0.0f, 0.0f);
    if (dy)
      *dy = make_float2(0.0f, 0.0f);

    return make_float2(0.0f, 0.0f);
  }
}

ccl_device float3 triangle_attribute_float3(KernelGlobals *kg,
                                            const ShaderData *sd,
                                            const AttributeDescriptor desc,
                                            float3 *dx,
                                            float3 *dy)
{
  if (desc.element == ATTR_ELEMENT_FACE) {
    if (dx)
      *dx = make_float3(0.0f, 0.0f, 0.0f);
    if (dy)
      *dy = make_float3(0.0f, 0.0f, 0.0f);

    return float4_to_float3(kernel_tex_fetch(__attributes_float3, desc.offset + sd->prim));
  }
  else if (desc.element == ATTR_ELEMENT_VERTEX || desc.element == ATTR_ELEMENT_VERTEX_MOTION) {
    uint4 tri_vindex = kernel_tex_fetch(__tri_vindex, sd->prim);

    float3 f0 = float4_to_float3(
        kernel_tex_fetch(__attributes_float3, desc.offset + tri_vindex.x));
    float3 f1 = float4_to_float3(
        kernel_tex_fetch(__attributes_float3, desc.offset + tri_vindex.y));
    float3 f2 = float4_to_float3(
        kernel_tex_fetch(__attributes_float3, desc.offset + tri_vindex.z));

#ifdef __RAY_DIFFERENTIALS__
    if (dx)
      *dx = sd->du.dx * f0 + sd->dv.dx * f1 - (sd->du.dx + sd->dv.dx) * f2;
    if (dy)
      *dy = sd->du.dy * f0 + sd->dv.dy * f1 - (sd->du.dy + sd->dv.dy) * f2;
#endif

    return sd->u * f0 + sd->v * f1 + (1.0f - sd->u - sd->v) * f2;
  }
  else if (desc.element == ATTR_ELEMENT_CORNER) {
    int tri = desc.offset + sd->prim * 3;
    float3 f0, f1, f2;

    f0 = float4_to_float3(kernel_tex_fetch(__attributes_float3, tri + 0));
    f1 = float4_to_float3(kernel_tex_fetch(__attributes_float3, tri + 1));
    f2 = float4_to_float3(kernel_tex_fetch(__attributes_float3, tri + 2));

#ifdef __RAY_DIFFERENTIALS__
    if (dx)
      *dx = sd->du.dx * f0 + sd->dv.dx * f1 - (sd->du.dx + sd->dv.dx) * f2;
    if (dy)
      *dy = sd->du.dy * f0 + sd->dv.dy * f1 - (sd->du.dy + sd->dv.dy) * f2;
#endif

    return sd->u * f0 + sd->v * f1 + (1.0f - sd->u - sd->v) * f2;
  }
  else {
    if (dx)
      *dx = make_float3(0.0f, 0.0f, 0.0f);
    if (dy)
      *dy = make_float3(0.0f, 0.0f, 0.0f);

    return make_float3(0.0f, 0.0f, 0.0f);
  }
}

ccl_device float4 triangle_attribute_float4(KernelGlobals *kg,
                                            const ShaderData *sd,
                                            const AttributeDescriptor desc,
                                            float4 *dx,
                                            float4 *dy)
{
  if (desc.element == ATTR_ELEMENT_CORNER_BYTE) {
    int tri = desc.offset + sd->prim * 3;

    float4 f0 = color_uchar4_to_float4(kernel_tex_fetch(__attributes_uchar4, tri + 0));
    float4 f1 = color_uchar4_to_float4(kernel_tex_fetch(__attributes_uchar4, tri + 1));
    float4 f2 = color_uchar4_to_float4(kernel_tex_fetch(__attributes_uchar4, tri + 2));

#ifdef __RAY_DIFFERENTIALS__
    if (dx)
      *dx = sd->du.dx * f0 + sd->dv.dx * f1 - (sd->du.dx + sd->dv.dx) * f2;
    if (dy)
      *dy = sd->du.dy * f0 + sd->dv.dy * f1 - (sd->du.dy + sd->dv.dy) * f2;
#endif

    return sd->u * f0 + sd->v * f1 + (1.0f - sd->u - sd->v) * f2;
  }
  else {
    if (dx)
      *dx = make_float4(0.0f, 0.0f, 0.0f, 0.0f);
    if (dy)
      *dy = make_float4(0.0f, 0.0f, 0.0f, 0.0f);

    return make_float4(0.0f, 0.0f, 0.0f, 0.0f);
  }
}

CCL_NAMESPACE_END
