370 lines
12 KiB
Rust
370 lines
12 KiB
Rust
use crate::core::bsdf::BSDFSample;
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use crate::core::bxdf::{BxDFFlags, BxDFReflTransFlags, BxDFTrait, FArgs, TransportMode};
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use crate::core::geometry::{
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Normal3f, Point2f, Vector3f, VectorLike, abs_cos_theta, cos_theta, same_hemisphere,
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};
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use crate::core::scattering::{
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TrowbridgeReitzDistribution, fr_complex_from_spectrum, fr_dielectric, reflect, refract,
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};
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use crate::spectra::SampledSpectrum;
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use crate::utils::math::square;
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use crate::utils::sampling::{cosine_hemisphere_pdf, sample_cosine_hemisphere};
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use crate::{Float, INV_PI};
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use core::any::Any;
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#[repr(C)]
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#[derive(Debug, Copy, Clone)]
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pub struct DielectricBxDF {
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pub eta: Float,
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pub mf_distrib: TrowbridgeReitzDistribution,
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}
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impl DielectricBxDF {
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pub fn new(eta: Float, mf_distrib: TrowbridgeReitzDistribution) -> Self {
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Self { eta, mf_distrib }
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}
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}
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impl BxDFTrait for DielectricBxDF {
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fn flags(&self) -> BxDFFlags {
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let flags = if self.eta == 1. {
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BxDFFlags::TRANSMISSION
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} else {
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BxDFFlags::REFLECTION | BxDFFlags::TRANSMISSION
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};
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flags
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| if self.mf_distrib.effectively_smooth() {
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BxDFFlags::SPECULAR
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} else {
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BxDFFlags::GLOSSY
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}
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}
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fn f(&self, wo: Vector3f, wi: Vector3f, mode: TransportMode) -> SampledSpectrum {
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if self.eta == 1. || self.mf_distrib.effectively_smooth() {
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return SampledSpectrum::new(0.);
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}
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// Generalized half vector wm
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let cos_theta_o = cos_theta(wo);
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let cos_theta_i = cos_theta(wi);
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let reflect = cos_theta_i * cos_theta_o > 0.;
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let mut etap = 1.;
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if !reflect {
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etap = if cos_theta_o > 0. {
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self.eta
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} else {
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1. / self.eta
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};
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}
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let wm_orig = wi * etap + wo;
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if cos_theta_i == 0. || cos_theta_o == 0. || wm_orig.norm_squared() == 0. {
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return SampledSpectrum::new(0.);
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}
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let wm = Normal3f::new(0., 0., 1.).face_forward(wm_orig.normalize());
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if wi.dot(wm.into()) * cos_theta_i < 0. || wo.dot(wm.into()) * cos_theta_o < 0. {
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return SampledSpectrum::new(0.);
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}
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let fr = fr_dielectric(wo.dot(wm.into()), self.eta);
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if reflect {
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SampledSpectrum::new(
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self.mf_distrib.d(wm.into()) * self.mf_distrib.g(wo, wi) * fr
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/ (4. * cos_theta_i * cos_theta_o).abs(),
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)
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} else {
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let denom =
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square(wi.dot(wm.into()) + wo.dot(wm.into()) / etap) * cos_theta_i * cos_theta_o;
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let mut ft = self.mf_distrib.d(wm.into())
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* (1. - fr)
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* self.mf_distrib.g(wo, wi)
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* (wi.dot(wm.into()) * wo.dot(wm.into()) / denom).abs();
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if mode == TransportMode::Radiance {
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ft /= square(etap)
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}
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SampledSpectrum::new(ft)
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}
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}
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fn pdf(&self, wo: Vector3f, wi: Vector3f, f_args: FArgs) -> Float {
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if self.eta == 1. || self.mf_distrib.effectively_smooth() {
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return 0.;
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}
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let cos_theta_o = cos_theta(wo);
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let cos_theta_i = cos_theta(wi);
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let reflect = cos_theta_i * cos_theta_o > 0.;
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let mut etap = 1.;
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if !reflect {
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etap = if cos_theta_o > 0. {
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self.eta
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} else {
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1. / self.eta
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};
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}
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let wm_orig = wi * etap + wo;
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if cos_theta_i == 0. || cos_theta_o == 0. || wm_orig.norm_squared() == 0. {
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return 0.;
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}
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let wm = Normal3f::new(0., 0., 1.).face_forward(wm_orig.normalize());
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// Discard backfacing microfacets
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if wi.dot(wm.into()) * cos_theta_i < 0. || wo.dot(wm.into()) * cos_theta_o < 0. {
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return 0.;
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}
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let r = fr_dielectric(wo.dot(wm.into()), self.eta);
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let t = 1. - r;
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let mut pr = r;
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let mut pt = t;
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let reflection_flags =
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BxDFReflTransFlags::from_bits_truncate(BxDFReflTransFlags::REFLECTION.bits());
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let transmission_flags =
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BxDFReflTransFlags::from_bits_truncate(BxDFReflTransFlags::TRANSMISSION.bits());
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if !f_args.sample_flags.contains(reflection_flags) {
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pr = 0.;
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}
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if !f_args.sample_flags.contains(transmission_flags) {
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pt = 0.;
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}
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if pr == 0. && pt == 0. {
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return 0.;
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}
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if reflect {
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self.mf_distrib.pdf(
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wo,
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Vector3f::from(wm) / (4. * wo.dot(wm.into()).abs()) * pr / (pt + pr),
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)
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} else {
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let denom = square(wi.dot(wm.into()) + wo.dot(wm.into()) / etap);
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let dwm_dwi = wi.dot(wm.into()).abs() / denom;
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self.mf_distrib.pdf(wo, wm.into()) * dwm_dwi * pr / (pr + pt)
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}
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}
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fn sample_f(&self, wo: Vector3f, uc: Float, u: Point2f, f_args: FArgs) -> Option<BSDFSample> {
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if self.eta == 1. || self.mf_distrib.effectively_smooth() {
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let r = fr_dielectric(cos_theta(wo), self.eta);
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let t = 1. - r;
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let mut pr = r;
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let mut pt = t;
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let reflection_flags =
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BxDFReflTransFlags::from_bits_truncate(BxDFReflTransFlags::REFLECTION.bits());
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let transmission_flags =
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BxDFReflTransFlags::from_bits_truncate(BxDFReflTransFlags::TRANSMISSION.bits());
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if !f_args.sample_flags.contains(reflection_flags) {
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pr = 0.;
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}
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if !f_args.sample_flags.contains(transmission_flags) {
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pt = 0.;
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}
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// If probabilities are null, doesnt contribute
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if pr == 0. && pt == 0. {
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return None;
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}
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if uc < pr / (pr + pt) {
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let wi = Vector3f::new(-wo.x(), -wo.y(), wo.z());
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let fr = SampledSpectrum::new(r / abs_cos_theta(wi));
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let bsdf = BSDFSample {
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f: fr,
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wi,
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pdf: pr / (pr + pt),
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flags: BxDFFlags::SPECULAR_REFLECTION,
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..Default::default()
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};
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Some(bsdf)
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} else {
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// Compute ray direction for specular transmission
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if let Some((wi, etap)) = refract(wo, Normal3f::new(0., 0., 1.), self.eta) {
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let mut ft = SampledSpectrum::new(t / abs_cos_theta(wi));
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if f_args.mode == TransportMode::Radiance {
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ft /= square(etap);
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}
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let bsdf = BSDFSample {
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f: ft,
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wi,
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pdf: pt / (pr + pt),
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flags: BxDFFlags::SPECULAR_TRANSMISSION,
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eta: etap,
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..Default::default()
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};
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Some(bsdf)
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} else {
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None
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}
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}
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} else {
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// Sample rough dielectric BSDF
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let wm = self.mf_distrib.sample_wm(wo, u);
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let r = fr_dielectric(wo.dot(wm), self.eta);
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let t = 1. - r;
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let mut pr = r;
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let mut pt = t;
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let reflection_flags =
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BxDFReflTransFlags::from_bits_truncate(BxDFReflTransFlags::REFLECTION.bits());
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let transmission_flags =
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BxDFReflTransFlags::from_bits_truncate(BxDFReflTransFlags::TRANSMISSION.bits());
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if !f_args.sample_flags.contains(reflection_flags) {
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pr = 0.;
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}
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if !f_args.sample_flags.contains(transmission_flags) {
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pt = 0.;
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}
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if pr == 0. && pt == 0. {
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return None;
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}
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let pdf: Float;
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if uc < pr / (pr + pt) {
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// Sample reflection at rough dielectric interface
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let wi = reflect(wo, wm.into());
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if !same_hemisphere(wo, wi) {
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return None;
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}
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pdf = self.mf_distrib.pdf(wo, wm) / (4. * wo.dot(wm).abs()) * pr / (pr + pt);
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let f = SampledSpectrum::new(
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self.mf_distrib.d(wm) * self.mf_distrib.g(wo, wi) * r
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/ (4. * cos_theta(wi) * cos_theta(wo)),
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);
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let bsdf = BSDFSample {
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f,
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wi,
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pdf,
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flags: BxDFFlags::GLOSSY_REFLECTION,
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..Default::default()
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};
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Some(bsdf)
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} else {
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// Sample transmission at rough dielectric interface
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if let Some((wi, etap)) = refract(wo, wm.into(), self.eta) {
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if same_hemisphere(wo, wi) || wi.z() == 0. {
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None
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} else {
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let denom = square(wi.dot(wm) + wo.dot(wm) / etap);
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let dwm_mi = wi.dot(wm).abs() / denom;
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pdf = self.mf_distrib.pdf(wo, wm) * dwm_mi * pt / (pr + pt);
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let mut ft = SampledSpectrum::new(
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t * self.mf_distrib.d(wm)
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* self.mf_distrib.g(wo, wi)
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* (wi.dot(wm) * wo.dot(wm)).abs()
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/ (cos_theta(wi) * cos_theta(wo) * denom),
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);
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if f_args.mode == TransportMode::Radiance {
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ft /= square(etap);
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}
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let bsdf = BSDFSample {
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f: ft,
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wi,
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pdf,
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flags: BxDFFlags::GLOSSY_TRANSMISSION,
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eta: etap,
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..Default::default()
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};
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Some(bsdf)
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}
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} else {
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None
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}
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}
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}
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}
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fn as_any(&self) -> &dyn Any {
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self
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}
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fn regularize(&mut self) {
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self.mf_distrib.regularize();
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}
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}
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#[repr(C)]
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#[derive(Debug, Copy, Clone)]
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pub struct ThinDielectricBxDF {
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pub eta: Float,
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}
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impl ThinDielectricBxDF {
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pub fn new(eta: Float) -> Self {
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Self { eta }
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}
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}
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impl BxDFTrait for ThinDielectricBxDF {
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fn flags(&self) -> BxDFFlags {
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BxDFFlags::REFLECTION | BxDFFlags::TRANSMISSION | BxDFFlags::SPECULAR
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}
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fn f(&self, _wo: Vector3f, _wi: Vector3f, _mode: TransportMode) -> SampledSpectrum {
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SampledSpectrum::new(0.)
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}
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fn pdf(&self, _wo: Vector3f, _wi: Vector3f, _f_args: FArgs) -> Float {
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0.
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}
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fn sample_f(&self, wo: Vector3f, uc: Float, _u: Point2f, f_args: FArgs) -> Option<BSDFSample> {
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let mut r = fr_dielectric(abs_cos_theta(wo), self.eta);
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let mut t = 1. - r;
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if r < 1. {
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r += square(t) * r / (1. - square(r));
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t = 1. - r;
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}
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let mut pr = r;
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let mut pt = t;
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let reflection_flags =
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BxDFReflTransFlags::from_bits_truncate(BxDFReflTransFlags::REFLECTION.bits());
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let transmission_flags =
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BxDFReflTransFlags::from_bits_truncate(BxDFReflTransFlags::TRANSMISSION.bits());
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if !f_args.sample_flags.contains(reflection_flags) {
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pr = 0.;
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}
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if !f_args.sample_flags.contains(transmission_flags) {
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pt = 0.;
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}
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if pr == 0. && pt == 0. {
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return None;
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}
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if uc < pr / (pr + pt) {
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let wi = Vector3f::new(-wo.x(), -wo.y(), wo.z());
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let f = SampledSpectrum::new(r / abs_cos_theta(wi));
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let bsdf = BSDFSample {
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f,
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wi,
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pdf: pr / (pr + pt),
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flags: BxDFFlags::SPECULAR_REFLECTION,
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..Default::default()
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};
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Some(bsdf)
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} else {
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// Perfect specular transmission
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let wi = -wo;
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let f = SampledSpectrum::new(t / abs_cos_theta(wi));
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let bsdf = BSDFSample {
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f,
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wi,
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pdf: pr / (pr + pt),
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flags: BxDFFlags::SPECULAR_TRANSMISSION,
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..Default::default()
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};
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Some(bsdf)
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}
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}
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fn as_any(&self) -> &dyn Any {
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self
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}
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fn regularize(&mut self) {
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todo!()
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}
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}
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