92 lines
3.4 KiB
Rust
92 lines
3.4 KiB
Rust
use nalgebra::{convert, Vector3};
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use super::colour::ColourRgbF;
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use super::raycasting::{IntersectionInfo, Ray};
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use super::sampler::Sampler;
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use super::util::algebra_utils::try_change_of_basis_matrix;
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use crate::Real;
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pub trait Integrator<T: Real> {
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fn integrate(
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&self,
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sampler: &Sampler<T>,
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info: &IntersectionInfo<T>,
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recursion_limit: u16,
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) -> ColourRgbF<T>;
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}
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pub struct DirectionalLight<T: Real> {
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pub direction: Vector3<T>,
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pub colour: ColourRgbF<T>,
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}
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pub struct WhittedIntegrator<T: Real> {
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pub ambient_light: ColourRgbF<T>,
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pub lights: Vec<DirectionalLight<T>>,
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}
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// TODO: Get rid of the magic bias number, which should be calculated base on expected error
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// bounds and tangent direction
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impl<T: Real> Integrator<T> for WhittedIntegrator<T> {
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fn integrate(
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&self,
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sampler: &Sampler<T>,
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info: &IntersectionInfo<T>,
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recursion_limit: u16,
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) -> ColourRgbF<T> {
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let world_to_bsdf_space =
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try_change_of_basis_matrix(&info.tangent, &info.cotangent, &info.normal)
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.expect("Normal, tangent and cotangent don't for a valid basis.");
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let bsdf_to_world_space = world_to_bsdf_space
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.try_inverse()
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.expect("Expected matrix to be invertable.");
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self.lights
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.iter()
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.map(|light| {
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match sampler
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.sample(&Ray::new(info.location, light.direction).bias(convert(0.000_000_1)))
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{
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Some(_) => self.ambient_light,
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None => {
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info.material.bsdf()(
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world_to_bsdf_space * info.retro,
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world_to_bsdf_space * light.direction,
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light.colour,
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) * light.direction.dot(&info.normal).abs()
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}
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}
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})
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.chain(
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info.material
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.sample(&(world_to_bsdf_space * info.retro))
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.iter()
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.map(|direction| {
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let world_space_direction = bsdf_to_world_space * direction;
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match sampler.sample(
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&Ray::new(info.location, world_space_direction)
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.bias(convert(0.000_000_1)),
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) {
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Some(recursive_hit) => {
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if recursion_limit > 0 {
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info.material.bsdf()(
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world_to_bsdf_space * info.retro,
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*direction,
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self.integrate(
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&sampler,
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&recursive_hit,
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recursion_limit - 1,
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),
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) * world_space_direction.dot(&info.normal).abs()
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} else {
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ColourRgbF::new(T::zero(), T::zero(), T::zero())
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}
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}
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None => ColourRgbF::new(T::zero(), T::zero(), T::zero()),
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}
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}),
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)
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.fold(self.ambient_light, |a, b| a + b)
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}
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}
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