size_t generate_environment_sample(
SamplingContext& sampling_context,
const EnvironmentEDF* env_edf,
SampleVector& samples)
{
// Sample the environment.
sampling_context.split_in_place(2, 1);
InputEvaluator input_evaluator(m_texture_cache);
Vector3d outgoing;
Spectrum env_edf_value;
double env_edf_prob;
env_edf->sample(
m_shading_context,
input_evaluator,
sampling_context.next_vector2<2>(),
outgoing, // points toward the environment
env_edf_value,
env_edf_prob);
// Uniformly sample the tangent disk.
sampling_context.split_in_place(2, 1);
const Vector2d p =
m_scene_radius
* sample_disk_uniform(sampling_context.next_vector2<2>());
// Compute the origin of the light ray.
const Basis3d basis(-outgoing);
const Vector3d ray_origin =
m_scene_center
- m_safe_scene_diameter * basis.get_normal()
+ p[0] * basis.get_tangent_u() +
+ p[1] * basis.get_tangent_v();
// Compute the initial particle weight.
Spectrum initial_flux = env_edf_value;
initial_flux /= static_cast<float>(m_disk_point_prob * env_edf_prob);
// Build the light ray.
sampling_context.split_in_place(1, 1);
const ShadingRay::Time time =
ShadingRay::Time::create_with_normalized_time(
sampling_context.next_double2(),
m_shutter_open_time,
m_shutter_close_time);
const ShadingRay light_ray(
ray_origin,
-outgoing,
time,
VisibilityFlags::LightRay,
0);
// Build the path tracer.
PathVisitor path_visitor(
m_params,
m_scene,
m_frame,
m_shading_context,
sampling_context,
samples,
initial_flux);
PathTracerType path_tracer(
path_visitor,
m_params.m_rr_min_path_length,
m_params.m_max_path_length,
m_params.m_max_iterations);
// Trace the light path.
const size_t path_length =
path_tracer.trace(
sampling_context,
m_shading_context,
light_ray);
// Update path statistics.
++m_path_count;
m_path_length.insert(path_length);
// Return the number of samples generated when tracing this light path.
return path_visitor.get_sample_count();
}
