void trace_emitting_triangle_photon(
SamplingContext& sampling_context,
LightSample& light_sample)
{
// Make sure the geometric normal of the light sample is in the same hemisphere as the shading normal.
light_sample.m_geometric_normal =
flip_to_same_hemisphere(
light_sample.m_geometric_normal,
light_sample.m_shading_normal);
const EDF* edf = light_sample.m_triangle->m_edf;
// Evaluate the EDF inputs.
InputEvaluator input_evaluator(m_texture_cache);
edf->evaluate_inputs(input_evaluator, light_sample.m_bary);
// Sample the EDF.
SamplingContext child_sampling_context = sampling_context.split(2, 1);
Vector3d emission_direction;
Spectrum edf_value;
double edf_prob;
edf->sample(
input_evaluator.data(),
light_sample.m_geometric_normal,
Basis3d(light_sample.m_shading_normal),
child_sampling_context.next_vector2<2>(),
emission_direction,
edf_value,
edf_prob);
// Compute the initial particle weight.
Spectrum initial_flux = edf_value;
initial_flux *=
static_cast<float>(
dot(emission_direction, light_sample.m_shading_normal)
/ (light_sample.m_probability * edf_prob * m_params.m_light_photon_count));
// Make a shading point that will be used to avoid self-intersections with the light sample.
ShadingPoint parent_shading_point;
light_sample.make_shading_point(
parent_shading_point,
emission_direction,
m_intersector);
// Build the photon ray.
child_sampling_context.split_in_place(1, 1);
const ShadingRay ray(
light_sample.m_point,
emission_direction,
child_sampling_context.next_double2(),
ShadingRay::LightRay);
// Build the path tracer.
const bool cast_indirect_light = (edf->get_flags() & EDF::CastIndirectLight) != 0;
PathVisitor path_visitor(
initial_flux,
m_params.m_dl_mode == SPPMParameters::SPPM, // store direct lighting photons?
cast_indirect_light,
m_params.m_enable_caustics,
m_local_photons);
PathTracer<PathVisitor, true> path_tracer( // true = adjoint
path_visitor,
m_params.m_photon_tracing_rr_min_path_length,
m_params.m_photon_tracing_max_path_length,
m_params.m_max_iterations,
edf->get_light_near_start()); // don't illuminate points closer than the light near start value
// Trace the photon path.
path_tracer.trace(
child_sampling_context,
m_shading_context,
ray,
&parent_shading_point);
}
size_t generate_emitting_triangle_sample(
SamplingContext& sampling_context,
LightSample& light_sample,
SampleVector& samples)
{
// Make sure the geometric normal of the light sample is in the same hemisphere as the shading normal.
light_sample.m_geometric_normal =
flip_to_same_hemisphere(
light_sample.m_geometric_normal,
light_sample.m_shading_normal);
const Material* material = light_sample.m_triangle->m_material;
const Material::RenderData& material_data = material->get_render_data();
// Build a shading point on the light source.
ShadingPoint light_shading_point;
light_sample.make_shading_point(
light_shading_point,
light_sample.m_shading_normal,
m_shading_context.get_intersector());
if (material_data.m_shader_group)
{
m_shading_context.execute_osl_emission(
*material_data.m_shader_group,
light_shading_point);
}
// Evaluate the EDF inputs.
InputEvaluator input_evaluator(m_texture_cache);
material_data.m_edf->evaluate_inputs(input_evaluator, light_shading_point);
// Sample the EDF.
sampling_context.split_in_place(2, 1);
Vector3f emission_direction;
Spectrum edf_value;
float edf_prob;
material_data.m_edf->sample(
sampling_context,
input_evaluator.data(),
Vector3f(light_sample.m_geometric_normal),
Basis3f(Vector3f(light_sample.m_shading_normal)),
sampling_context.next2<Vector2f>(),
emission_direction,
edf_value,
edf_prob);
// Compute the initial particle weight.
Spectrum initial_flux = edf_value;
initial_flux *=
dot(emission_direction, Vector3f(light_sample.m_shading_normal)) /
(light_sample.m_probability * edf_prob);
// Make a shading point that will be used to avoid self-intersections with the light sample.
ShadingPoint parent_shading_point;
light_sample.make_shading_point(
parent_shading_point,
Vector3d(emission_direction),
m_intersector);
// Build the light ray.
sampling_context.split_in_place(1, 1);
const ShadingRay::Time time =
ShadingRay::Time::create_with_normalized_time(
sampling_context.next2<float>(),
m_shutter_open_time,
m_shutter_close_time);
const ShadingRay light_ray(
light_sample.m_point,
Vector3d(emission_direction),
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,
material_data.m_edf->get_light_near_start()); // don't illuminate points closer than the light near start value
// Handle the light vertex separately.
Spectrum light_particle_flux = edf_value; // todo: only works for diffuse EDF? What we need is the light exitance
light_particle_flux /= light_sample.m_probability;
path_visitor.visit_area_light_vertex(
light_sample,
light_particle_flux,
light_ray.m_time);
// Trace the light path.
const size_t path_length =
path_tracer.trace(
sampling_context,
m_shading_context,
light_ray,
&parent_shading_point);
// 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();
}
spectrum PathTracerIntegrator::_trace_ray(const Scene& scene, const Ray& ray,
Sampler& sampler, int depth) const
{
++rays_traced;
if (depth == 1)
++primary_rays_traced;
auto isect_opt = scene.intersect(ray);
const Vec3 ray_dir_origin = -ray.direction.normal();
if (!isect_opt.is())
return scene.environment_light_emission(-ray_dir_origin);
auto isect = isect_opt.get();
spectrum total(0);
total += isect.emission();
// direct lighting: randomly choose a light, and contribute
// the light from that shape if appropriate
scalar light_prob;
const auto light = scene.sample_light(sampler.sample_1d(), light_prob);
if (light_prob > 0)
{
LightSample ls = light->sample_emission(isect, sampler);
if (ls && ls.p() > 0)
{
if (!ls.is_occluded(scene))
{
scalar NL = max<scalar>(ls.direction().dot(isect.normal), 0.0);
auto ca = isect.reflectance(ls.direction(), ray_dir_origin);
auto light_contrib = ls.emission() * ca * spectrum{NL / (light_prob * ls.p())};
total += light_contrib;
}
}
}
// Decide whether or not to continue trace and, if so, what the multiplier
// should be.
bool continue_trace = true;
scalar p_mult = 1.0;
if (opt.max_depth > 0 && depth >= opt.max_depth)
continue_trace = false;
else if (opt.russian_roulette && depth >= opt.min_rr_depth)
{
if (sampler.sample_1d() < opt.rr_kill_prob)
{
continue_trace = false;
}
else
{
p_mult /= (1 - opt.rr_kill_prob);
}
}
if (continue_trace)
{
auto mat_sample = isect.sample_bsdf(ray_dir_origin, sampler);
scalar nl = fabs(mat_sample.direction.dot(isect.normal));// max<scalar>(brdf_dir.dot(isect.normal), 0);
if (mat_sample.prob > 0 && nl > 0)
{
total += _trace_ray(scene, Ray{isect.position, mat_sample.direction}.nudge(),
sampler, depth + 1) *
mat_sample.reflectance *
spectrum{p_mult / mat_sample.prob * nl};
}
}
return total;
}
size_t generate_emitting_triangle_sample(
SamplingContext& sampling_context,
LightSample& light_sample,
SampleVector& samples)
{
// Make sure the geometric normal of the light sample is in the same hemisphere as the shading normal.
light_sample.m_geometric_normal =
flip_to_same_hemisphere(
light_sample.m_geometric_normal,
light_sample.m_shading_normal);
const Material* material = light_sample.m_triangle->m_material;
const EDF* edf = material->get_edf();
// Evaluate the EDF inputs.
InputEvaluator input_evaluator(m_texture_cache);
// TODO: refactor this code (est.).
ShadingPoint shading_point;
light_sample.make_shading_point(
shading_point,
light_sample.m_shading_normal,
m_shading_context.get_intersector());
#ifdef WITH_OSL
if (const ShaderGroup* sg = material->get_osl_surface())
{
// TODO: get object area somehow.
const float surface_area = 0.0f;
m_shading_context.execute_osl_emission(*sg, shading_point, surface_area);
}
#endif
edf->evaluate_inputs(input_evaluator, shading_point);
// Sample the EDF.
sampling_context.split_in_place(2, 1);
Vector3d emission_direction;
Spectrum edf_value;
double edf_prob;
edf->sample(
sampling_context,
input_evaluator.data(),
light_sample.m_geometric_normal,
Basis3d(light_sample.m_shading_normal),
sampling_context.next_vector2<2>(),
emission_direction,
edf_value,
edf_prob);
// Compute the initial particle weight.
Spectrum initial_flux = edf_value;
initial_flux *=
static_cast<float>(
dot(emission_direction, light_sample.m_shading_normal)
/ (light_sample.m_probability * edf_prob));
// Make a shading point that will be used to avoid self-intersections with the light sample.
ShadingPoint parent_shading_point;
light_sample.make_shading_point(
parent_shading_point,
emission_direction,
m_intersector);
// Build the light ray.
sampling_context.split_in_place(1, 1);
const ShadingRay light_ray(
light_sample.m_point,
emission_direction,
sampling_context.next_double2(),
m_ray_dtime,
ShadingRay::LightRay);
// Build the path tracer.
PathVisitor path_visitor(
m_params,
m_scene,
m_frame,
m_shading_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,
edf->get_light_near_start()); // don't illuminate points closer than the light near start value
// Handle the light vertex separately.
Spectrum light_particle_flux = edf_value; // todo: only works for diffuse EDF? What we need is the light exitance
light_particle_flux /= static_cast<float>(light_sample.m_probability);
path_visitor.visit_area_light_vertex(
light_sample,
light_particle_flux,
light_ray.m_time);
// Trace the light path.
const size_t path_length =
path_tracer.trace(
sampling_context,
m_shading_context,
light_ray,
&parent_shading_point);
// 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();
}
void DirectLightingIntegrator::add_emitting_triangle_sample_contribution(
const LightSample& sample,
const MISHeuristic mis_heuristic,
const Dual3d& outgoing,
Spectrum& radiance,
SpectrumStack& aovs) const
{
const Material* material = sample.m_triangle->m_material;
const Material::RenderData& material_data = material->get_render_data();
const EDF* edf = material_data.m_edf;
// No contribution if we are computing indirect lighting but this light does not cast indirect light.
if (m_indirect && !(edf->get_flags() & EDF::CastIndirectLight))
return;
// Compute the incoming direction in world space.
Vector3d incoming = sample.m_point - m_point;
// Cull light samples behind the shading surface if the BSDF is either reflective or transmissive,
// but not both.
if (m_bsdf.get_type() != BSDF::AllBSDFTypes)
{
double cos_in = dot(incoming, m_shading_basis.get_normal());
if (m_bsdf.get_type() == BSDF::Transmissive)
cos_in = -cos_in;
if (cos_in <= 0.0)
return;
}
// No contribution if the shading point is behind the light.
double cos_on = dot(-incoming, sample.m_shading_normal);
if (cos_on <= 0.0)
return;
// Compute the transmission factor between the light sample and the shading point.
const double transmission =
m_shading_context.get_tracer().trace_between(
m_shading_point,
sample.m_point,
VisibilityFlags::ShadowRay);
// Discard occluded samples.
if (transmission == 0.0)
return;
// Compute the square distance between the light sample and the shading point.
const double square_distance = square_norm(incoming);
const double rcp_sample_square_distance = 1.0 / square_distance;
const double rcp_sample_distance = sqrt(rcp_sample_square_distance);
// Don't use this sample if we're closer than the light near start value.
if (square_distance < square(edf->get_light_near_start()))
return;
// Normalize the incoming direction.
incoming *= rcp_sample_distance;
cos_on *= rcp_sample_distance;
// Evaluate the BSDF.
Spectrum bsdf_value;
const double bsdf_prob =
m_bsdf.evaluate(
m_bsdf_data,
false, // not adjoint
true, // multiply by |cos(incoming, normal)|
m_geometric_normal,
m_shading_basis,
outgoing.get_value(),
incoming,
m_light_sampling_modes,
bsdf_value);
if (bsdf_prob == 0.0)
return;
// Build a shading point on the light source.
ShadingPoint light_shading_point;
sample.make_shading_point(
light_shading_point,
sample.m_shading_normal,
m_shading_context.get_intersector());
#ifdef APPLESEED_WITH_OSL
if (material_data.m_shader_group)
{
m_shading_context.execute_osl_emission(
*material_data.m_shader_group,
light_shading_point);
}
#endif
// Evaluate the EDF inputs.
InputEvaluator edf_input_evaluator(m_shading_context.get_texture_cache());
edf->evaluate_inputs(edf_input_evaluator, light_shading_point);
// Evaluate the EDF.
Spectrum edf_value;
edf->evaluate(
edf_input_evaluator.data(),
sample.m_geometric_normal,
Basis3d(sample.m_shading_normal),
-incoming,
edf_value);
const double g = cos_on * rcp_sample_square_distance;
double weight = transmission * g / sample.m_probability;
// Apply MIS weighting.
weight *=
mis(
mis_heuristic,
m_light_sample_count * sample.m_probability,
m_bsdf_sample_count * bsdf_prob * g);
// Add the contribution of this sample to the illumination.
edf_value *= static_cast<float>(weight);
edf_value *= bsdf_value;
radiance += edf_value;
aovs.add(edf->get_render_layer_index(), edf_value);
}
bool DirectLightingIntegrator::compute_incoming_radiance(
SamplingContext& sampling_context,
Vector3d& incoming,
double& incoming_prob,
Spectrum& radiance) const
{
if (!m_light_sampler.has_lights_or_emitting_triangles())
return false;
sampling_context.split_in_place(3, 1);
const Vector3d s = sampling_context.next_vector2<3>();
LightSample sample;
m_light_sampler.sample(m_time, s, sample);
if (sample.m_triangle)
{
const Material* material = sample.m_triangle->m_material;
const Material::RenderData& material_data = material->get_render_data();
const EDF* edf = material_data.m_edf;
// No contribution if we are computing indirect lighting but this light does not cast indirect light.
if (m_indirect && !(edf->get_flags() & EDF::CastIndirectLight))
return false;
// Compute the incoming direction in world space.
incoming = sample.m_point - m_point;
// No contribution if the shading point is behind the light.
double cos_on_light = dot(-incoming, sample.m_shading_normal);
if (cos_on_light <= 0.0)
return false;
// Compute the transmission factor between the light sample and the shading point.
const double transmission =
m_shading_context.get_tracer().trace_between(
m_shading_point,
sample.m_point,
VisibilityFlags::ShadowRay);
// Discard occluded samples.
if (transmission == 0.0)
return false;
// Don't use this sample if we're closer than the light near start value.
const double square_distance = square_norm(incoming);
if (square_distance < square(edf->get_light_near_start()))
return false;
// Normalize the incoming direction.
const double rcp_square_distance = 1.0 / square_distance;
const double rcp_distance = sqrt(rcp_square_distance);
incoming *= rcp_distance;
cos_on_light *= rcp_distance;
// Build a shading point on the light source.
ShadingPoint light_shading_point;
sample.make_shading_point(
light_shading_point,
sample.m_shading_normal,
m_shading_context.get_intersector());
#ifdef APPLESEED_WITH_OSL
if (material_data.m_shader_group)
{
m_shading_context.execute_osl_emission(
*material_data.m_shader_group,
light_shading_point);
}
#endif
// Evaluate the EDF inputs.
InputEvaluator edf_input_evaluator(m_shading_context.get_texture_cache());
edf->evaluate_inputs(edf_input_evaluator, light_shading_point);
// Evaluate the EDF.
edf->evaluate(
edf_input_evaluator.data(),
sample.m_geometric_normal,
Basis3d(sample.m_shading_normal),
-incoming,
radiance);
// Compute probability with respect to solid angle of incoming direction.
const double g = cos_on_light * rcp_square_distance;
incoming_prob = sample.m_probability / g;
// Compute and return the incoming radiance.
radiance *= static_cast<float>(transmission * g / sample.m_probability);
}
else
{
const Light* light = sample.m_light;
// No contribution if we are computing indirect lighting but this light does not cast indirect light.
if (m_indirect && !(light->get_flags() & Light::CastIndirectLight))
return false;
// Evaluate the light.
InputEvaluator input_evaluator(m_shading_context.get_texture_cache());
Vector3d emission_position, emission_direction;
light->evaluate(
input_evaluator,
sample.m_light_transform,
m_point,
emission_position,
emission_direction,
radiance);
// Compute the transmission factor between the light sample and the shading point.
const double transmission =
m_shading_context.get_tracer().trace_between(
m_shading_point,
emission_position,
VisibilityFlags::ShadowRay);
// Discard occluded samples.
if (transmission == 0.0)
return false;
// Compute the incoming direction in world space.
incoming = -emission_direction;
incoming_prob = BSDF::DiracDelta;
// Compute and return the incoming radiance.
const double attenuation = light->compute_distance_attenuation(m_point, emission_position);
radiance *= static_cast<float>(transmission * attenuation / sample.m_probability);
}
return true;
}
void DirectLightingIntegrator::add_emitting_shape_sample_contribution(
SamplingContext& sampling_context,
const LightSample& sample,
const MISHeuristic mis_heuristic,
const Dual3d& outgoing,
DirectShadingComponents& radiance,
LightPathStream* light_path_stream) const
{
const Material* material = sample.m_shape->get_material();
const Material::RenderData& material_data = material->get_render_data();
const EDF* edf = material_data.m_edf;
// No contribution if we are computing indirect lighting but this light does not cast indirect light.
if (m_indirect && !(edf->get_flags() & EDF::CastIndirectLight))
return;
// Compute the incoming direction in world space.
Vector3d incoming = sample.m_point - m_material_sampler.get_point();
// No contribution if the shading point is behind the light.
double cos_on = dot(-incoming, sample.m_shading_normal);
if (cos_on <= 0.0)
return;
// Compute the square distance between the light sample and the shading point.
const double square_distance = square_norm(incoming);
// Don't use this sample if we're closer than the light near start value.
if (square_distance < square(edf->get_light_near_start()))
return;
const double rcp_sample_square_distance = 1.0 / square_distance;
const double rcp_sample_distance = sqrt(rcp_sample_square_distance);
// Normalize the incoming direction.
cos_on *= rcp_sample_distance;
incoming *= rcp_sample_distance;
// Probabilistically skip light samples with low maximum contribution.
float contribution_prob = 1.0f;
if (m_low_light_threshold > 0.0f)
{
// Compute the approximate maximum contribution of this light sample.
const float max_contribution =
static_cast<float>(
cos_on *
rcp_sample_square_distance *
sample.m_shape->get_max_flux());
// Use Russian Roulette to skip this sample if its maximum contribution is low.
if (max_contribution < m_low_light_threshold)
{
// Generate a uniform sample in [0,1).
SamplingContext child_sampling_context = sampling_context.split(1, 1);
const float s = child_sampling_context.next2<float>();
// Compute the probability of taking the sample's contribution into account.
contribution_prob = max_contribution / m_low_light_threshold;
// Russian Roulette.
if (!pass_rr(contribution_prob, s))
return;
}
}
// Compute the transmission factor between the light sample and the shading point.
Spectrum transmission;
m_material_sampler.trace_between(
m_shading_context,
sample.m_point,
transmission);
// Discard occluded samples.
if (is_zero(transmission))
return;
// Evaluate the BSDF (or volume).
DirectShadingComponents material_value;
const float material_probability =
m_material_sampler.evaluate(
Vector3f(outgoing.get_value()),
Vector3f(incoming),
m_light_sampling_modes,
material_value);
assert(material_probability >= 0.0f);
if (material_probability == 0.0f)
return;
// Build a shading point on the light source.
ShadingPoint light_shading_point;
sample.make_shading_point(
light_shading_point,
sample.m_shading_normal,
m_shading_context.get_intersector());
if (material_data.m_shader_group)
{
m_shading_context.execute_osl_emission(
*material_data.m_shader_group,
light_shading_point);
}
// Evaluate the EDF.
Spectrum edf_value(Spectrum::Illuminance);
edf->evaluate(
edf->evaluate_inputs(m_shading_context, light_shading_point),
Vector3f(sample.m_geometric_normal),
Basis3f(Vector3f(sample.m_shading_normal)),
-Vector3f(incoming),
edf_value);
const float g = static_cast<float>(cos_on * rcp_sample_square_distance);
// Apply MIS weighting.
const float mis_weight =
mis(
mis_heuristic,
m_light_sample_count * sample.m_probability,
m_material_sample_count * material_probability * g);
// Add the contribution of this sample to the illumination.
edf_value *= transmission;
edf_value *= (mis_weight * g) / (sample.m_probability * contribution_prob);
madd(radiance, material_value, edf_value);
// Record light path event.
if (light_path_stream)
{
light_path_stream->sampled_emitting_shape(
*sample.m_shape,
sample.m_point,
material_value.m_beauty,
edf_value);
}
}