text: /*
  * Copyright 2011-2018 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.
  */
  
  CCL_NAMESPACE_BEGIN
  
  ccl_device_noinline float svm_ao(KernelGlobals *kg,
                                   ShaderData *sd,
                                   float3 N,
                                   ccl_addr_space PathState *state,
                                   float max_dist,
                                   int num_samples,
                                   int flags)
  {
    if (flags & NODE_AO_GLOBAL_RADIUS) {
      max_dist = kernel_data.background.ao_distance;
    }
  
    /* Early out if no sampling needed. */
    if (max_dist <= 0.0f || num_samples < 1 || sd->object == OBJECT_NONE) {
      return 1.0f;
    }
  
    /* Can't raytrace from shaders like displacement, before BVH exists. */
    if (kernel_data.bvh.bvh_layout == BVH_LAYOUT_NONE) {
      return 1.0f;
    }
  
    if (flags & NODE_AO_INSIDE) {
      N = -N;
    }
  
    float3 T, B;
    make_orthonormals(N, &T, &B);
  
    int unoccluded = 0;
    for (int sample = 0; sample < num_samples; sample++) {
      float disk_u, disk_v;
      path_branched_rng_2D(
          kg, state->rng_hash, state, sample, num_samples, PRNG_BEVEL_U, &disk_u, &disk_v);
  
      float2 d = concentric_sample_disk(disk_u, disk_v);
      float3 D = make_float3(d.x, d.y, safe_sqrtf(1.0f - dot(d, d)));
  
      /* Create ray. */
      Ray ray;
      ray.P = ray_offset(sd->P, N);
      ray.D = D.x * T + D.y * B + D.z * N;
      ray.t = max_dist;
      ray.time = sd->time;
      ray.dP = sd->dP;
      ray.dD = differential3_zero();
  
      if (flags & NODE_AO_ONLY_LOCAL) {
        if (!scene_intersect_local(kg, ray, NULL, sd->object, NULL, 0)) {
          unoccluded++;
        }
      }
      else {
        Intersection isect;
        if (!scene_intersect(kg, ray, PATH_RAY_SHADOW_OPAQUE, &isect, NULL, 0.0f, 0.0f)) {
          unoccluded++;
        }
      }
    }
  
    return ((float)unoccluded) / num_samples;
  }
  
  ccl_device void svm_node_ao(
      KernelGlobals *kg, ShaderData *sd, ccl_addr_space PathState *state, float *stack, uint4 node)
  {
    uint flags, dist_offset, normal_offset, out_ao_offset;
    decode_node_uchar4(node.y, &flags, &dist_offset, &normal_offset, &out_ao_offset);
  
    uint color_offset, out_color_offset, samples;
    decode_node_uchar4(node.z, &color_offset, &out_color_offset, &samples, NULL);
  
    float dist = stack_load_float_default(stack, dist_offset, node.w);
    float3 normal = stack_valid(normal_offset) ? stack_load_float3(stack, normal_offset) : sd->N;
    float ao = svm_ao(kg, sd, normal, state, dist, samples, flags);
  
    if (stack_valid(out_ao_offset)) {
      stack_store_float(stack, out_ao_offset, ao);
    }
  
    if (stack_valid(out_color_offset)) {
      float3 color = stack_load_float3(stack, color_offset);
      stack_store_float3(stack, out_color_offset, ao * color);
    }
  }
  
  CCL_NAMESPACE_END
  