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// std
use std::cell::Cell;
use std::sync::Arc;
// pbrt
// use crate::core::bssrdf::Bssrdf;
use crate::core::camera::Camera;
use crate::core::geometry::{vec3_abs_dot_nrmf, vec3_dot_nrmf};
use crate::core::geometry::{Bounds2i, Point2f, Ray, Vector3f};
use crate::core::integrator::uniform_sample_one_light;
use crate::core::interaction::{Interaction, MediumInteraction, SurfaceInteraction};
use crate::core::lightdistrib::create_light_sample_distribution;
use crate::core::lightdistrib::LightDistribution;
use crate::core::material::TransportMode;
use crate::core::pbrt::{Float, Spectrum};
use crate::core::reflection::BxdfType;
use crate::core::sampler::Sampler;
use crate::core::sampling::Distribution1D;
use crate::core::scene::Scene;
// see volpath.h
/// Accounts for scattering and attenuation from participating media
/// as well as scattering from surfaces - uses the render loop of a
/// [SamplerIntegrator](../../core/integrator/enum.SamplerIntegrator.html)
pub struct VolPathIntegrator {
// inherited from SamplerIntegrator (see integrator.h)
pub camera: Arc<Camera>,
pub sampler: Box<Sampler>,
pub pixel_bounds: Bounds2i,
// see volpath.h
pub max_depth: u32,
pub rr_threshold: Float, // 1.0
pub light_sample_strategy: String, // "spatial"
pub light_distribution: Option<Arc<LightDistribution>>,
}
impl VolPathIntegrator {
pub fn new(
max_depth: u32,
camera: Arc<Camera>,
sampler: Box<Sampler>,
pixel_bounds: Bounds2i,
rr_threshold: Float,
light_sample_strategy: String,
) -> Self {
VolPathIntegrator {
camera,
sampler,
pixel_bounds,
max_depth,
rr_threshold,
light_sample_strategy,
light_distribution: None,
}
}
pub fn preprocess(&mut self, scene: &Scene) {
self.light_distribution =
create_light_sample_distribution(self.light_sample_strategy.clone(), scene);
}
pub fn li(
&self,
r: &mut Ray,
scene: &Scene,
sampler: &mut Sampler,
// arena: &mut Arena,
_depth: i32,
) -> Spectrum {
// TODO: ProfilePhase p(Prof::SamplerIntegratorLi);
let mut l: Spectrum = Spectrum::default();
let mut beta: Spectrum = Spectrum::new(1.0 as Float);
let mut ray: Ray = Ray {
o: r.o,
d: r.d,
t_max: Cell::new(r.t_max.get()),
time: r.time,
differential: r.differential,
medium: r.medium.clone(),
};
let mut specular_bounce: bool = false;
let mut bounces: u32 = 0_u32;
// Added after book publication: etaScale tracks the
// accumulated effect of radiance scaling due to rays passing
// through refractive boundaries (see the derivation on p. 527
// of the third edition). We track this value in order to
// remove it from beta when we apply Russian roulette; this is
// worthwhile, since it lets us sometimes avoid terminating
// refracted rays that are about to be refracted back out of a
// medium and thus have their beta value increased.
let mut eta_scale: Float = 1.0;
loop {
let mut mi_opt: Option<MediumInteraction> = None;
// intersect _ray_ with scene and store intersection in _isect_
let mut isect: SurfaceInteraction = SurfaceInteraction::default();
if scene.intersect(&mut ray, &mut isect) {
// sample the participating medium, if present
if let Some(ref medium) = ray.medium {
let (spectrum, option) = medium.sample(&ray, sampler);
beta *= spectrum;
if let Some(mi) = option {
mi_opt = Some(mi);
}
}
if beta.is_black() {
break;
}
// handle an interaction with a medium or a surface
if let Some(mi) = mi_opt {
// terminate path if ray escaped or _maxDepth_ was reached
if bounces >= self.max_depth {
break;
}
let mi_p = mi.common.p;
// if mi.is_valid() {...}
if let Some(phase) = mi.clone().phase {
// TODO: ++volumeInteractions;
// handle scattering at point in medium for volumetric path tracer
if let Some(ref light_distribution) = self.light_distribution {
let distrib: Arc<Distribution1D> = light_distribution.lookup(&mi_p);
l += beta
* uniform_sample_one_light(
&mi as &dyn Interaction,
scene,
sampler,
true,
Some(&distrib),
);
let mut wi: Vector3f = Vector3f::default();
phase.sample_p(&(-ray.d), &mut wi, sampler.get_2d());
ray = mi.spawn_ray(&wi);
specular_bounce = false;
}
}
} else {
// TODO: ++surfaceInteractions;
// possibly add emitted light at intersection
if bounces == 0 || specular_bounce {
// add emitted light at path vertex
l += beta * isect.le(&-ray.d);
}
// terminate path if _maxDepth_ was reached
if bounces >= self.max_depth {
break;
}
// compute scattering functions and skip over medium boundaries
let mode: TransportMode = TransportMode::Radiance;
isect.compute_scattering_functions(&ray, true, mode);
if let Some(ref _bsdf) = isect.bsdf {
// we are fine (for below)
} else {
ray = isect.spawn_ray(&ray.d);
// bounces--;
continue;
}
if let Some(ref light_distribution) = self.light_distribution {
let light_distrib: Arc<Distribution1D> =
light_distribution.lookup(&isect.common.p);
// Sample illumination from lights to find
// attenuated path contribution.
let it: &SurfaceInteraction = &isect;
l += beta
* uniform_sample_one_light(
it,
scene,
sampler,
true,
Some(&light_distrib),
);
if let Some(ref bsdf) = isect.bsdf {
// Sample BSDF to get new path direction
let wo: Vector3f = -ray.d;
let mut wi: Vector3f = Vector3f::default();
let mut pdf: Float = 0.0 as Float;
let bsdf_flags: u8 = BxdfType::BsdfAll as u8;
let mut sampled_type: u8 = u8::max_value(); // != 0
let f: Spectrum = bsdf.sample_f(
&wo,
&mut wi,
&sampler.get_2d(),
&mut pdf,
bsdf_flags,
&mut sampled_type,
);
if f.is_black() || pdf == 0.0 as Float {
break;
}
beta *= (f * vec3_abs_dot_nrmf(&wi, &isect.shading.n)) / pdf;
assert!(
!(beta.y().is_infinite()),
"[{:#?}, {:?}] = ({:#?} * dot({:#?}, {:#?})) / {:?}",
sampler.get_current_pixel(),
sampler.get_current_sample_number(),
f,
wi,
isect.shading.n,
pdf
);
specular_bounce = (sampled_type & BxdfType::BsdfSpecular as u8) != 0_u8;
if ((sampled_type & BxdfType::BsdfSpecular as u8) != 0_u8)
&& ((sampled_type & BxdfType::BsdfTransmission as u8) != 0_u8)
{
let eta: Float = bsdf.eta;
// Update the term that tracks radiance
// scaling for refraction depending on
// whether the ray is entering or leaving
// the medium.
if vec3_dot_nrmf(&wo, &isect.common.n) > 0.0 as Float {
eta_scale *= eta * eta;
} else {
eta_scale *= 1.0 as Float / (eta * eta);
}
}
ray = isect.spawn_ray(&wi);
// account for attenuated subsurface scattering, if applicable
if let Some(ref bssrdf) = isect.bssrdf {
if (sampled_type & BxdfType::BsdfTransmission as u8) != 0_u8 {
// importance sample the BSSRDF
let s2: Point2f = sampler.get_2d();
let s1: Float = sampler.get_1d();
let (s, pi_opt) = bssrdf.sample_s(
// the next three (extra) parameters are used for SeparableBssrdfAdapter
bssrdf.clone(),
bssrdf.mode,
bssrdf.eta,
// done
scene,
s1,
s2,
&mut pdf,
);
if s.is_black() || pdf == 0.0 as Float {
break;
}
assert!(!(beta.y().is_infinite()));
beta *= s / pdf;
if let Some(pi) = pi_opt {
// account for the direct subsurface scattering component
let distrib: Arc<Distribution1D> =
light_distribution.lookup(&pi.common.p);
l += beta
* uniform_sample_one_light(
&pi,
scene,
sampler,
true,
Some(&distrib),
);
// account for the indirect subsurface scattering component
let mut wi: Vector3f = Vector3f::default();
let mut pdf: Float = 0.0 as Float;
let bsdf_flags: u8 = BxdfType::BsdfAll as u8;
let mut sampled_type: u8 = u8::max_value(); // != 0
if let Some(ref bsdf) = pi.bsdf {
let f: Spectrum = bsdf.sample_f(
&pi.common.wo,
&mut wi,
&sampler.get_2d(),
&mut pdf,
bsdf_flags,
&mut sampled_type,
);
if f.is_black() || pdf == 0.0 as Float {
break;
}
beta *= f * vec3_abs_dot_nrmf(&wi, &pi.shading.n) / pdf;
assert!(!(beta.y().is_infinite()));
specular_bounce = (sampled_type
& BxdfType::BsdfSpecular as u8)
!= 0_u8;
ray = pi.spawn_ray(&wi);
} else {
panic!("no pi.bsdf found");
}
} else {
panic!("bssrdf.sample_s() did return (s, None)");
}
}
}
} else {
println!("TODO: if let Some(ref bsdf) = isect.bsdf failed");
}
}
}
// Possibly terminate the path with Russian roulette.
// Factor out radiance scaling due to refraction in rr_beta.
let rr_beta: Spectrum = beta * eta_scale;
if rr_beta.max_component_value() < self.rr_threshold && bounces > 3 {
let q: Float =
(0.05 as Float).max(1.0 as Float - rr_beta.max_component_value());
if sampler.get_1d() < q {
break;
}
beta /= 1.0 as Float - q;
assert!(!(beta.y().is_infinite()));
}
} else {
// sample the participating medium, if present
if let Some(ref medium) = ray.medium {
let (spectrum, option) = medium.sample(&ray, sampler);
beta *= spectrum;
if let Some(mi) = option {
mi_opt = Some(mi);
}
}
if beta.is_black() {
break;
}
// handle an interaction with a medium
if let Some(mi) = mi_opt {
// terminate path if ray escaped or _maxDepth_ was reached
if bounces >= self.max_depth {
break;
}
let mi_p = mi.common.p;
// if mi.is_valid() {...}
if let Some(phase) = mi.clone().phase {
// TODO: ++volumeInteractions;
// handle scattering at point in medium for volumetric path tracer
if let Some(ref light_distribution) = self.light_distribution {
let distrib: Arc<Distribution1D> = light_distribution.lookup(&mi_p);
l += beta
* uniform_sample_one_light(
&mi as &dyn Interaction,
scene,
sampler,
true,
Some(&distrib),
);
let mut wi: Vector3f = Vector3f::default();
phase.sample_p(&(-ray.d), &mut wi, sampler.get_2d());
ray = mi.spawn_ray(&wi);
specular_bounce = false;
}
}
}
// add emitted light from the environment
if bounces == 0 || specular_bounce {
for light in &scene.infinite_lights {
l += beta * light.le(&mut ray);
}
}
// terminate path if ray escaped
break;
}
bounces += 1_u32;
}
l
}
pub fn get_camera(&self) -> Arc<Camera> {
self.camera.clone()
}
pub fn get_sampler(&self) -> &Sampler {
&self.sampler
}
pub fn get_pixel_bounds(&self) -> Bounds2i {
self.pixel_bounds
}
}