Material class
#include <darts/material.h>

A base class used to represent surface material properties.

Derived classes

class Dielectric
A smooth dielectric surface that reflects and refracts light according to the specified index of refraction ior.
class Diffuse
A perfectly diffuse material.
class Emission
A material that emits light equally in all directions from the front side of a surface.
class Metal
A metallic material that reflects light into the (potentially rough) mirror reflection direction.

Constructors, destructors, conversion operators

Material(const json& j = json::object())
Default constructor which accepts a json object of named parameters.
~Material() defaulted virtual
Free all memory.

Public functions

auto scatter(const Ray3f& ray, const HitRecord& hit, Color3f& attenuation, Ray3f& scattered) const -> bool virtual
Compute the scattered direction scattered at a surface hitpoint.
auto emitted(const Ray3f& ray, const HitRecord& hit) const -> Color3f virtual
Compute the amount of emitted light at the surface hitpoint.
auto sample(const Ray3f& ray, const HitRecord& hit, ScatterRecord& srec, const Vec2f& rv, float rv1) const -> bool virtual
Sample a scattered direction at the surface hitpoint hit.
auto eval(const Ray3f& ray, const Vec3f& scattered, const HitRecord& hit) const -> Color3f virtual
Evaluate the material response for the given pair of directions.
auto pdf(const Ray3f& ray, const Vec3f& scattered, const HitRecord& hit) const -> float virtual
Compute the probability density that sample() will generate scattered (given wi).

Function documentation

bool Material::scatter(const Ray3f& ray, const HitRecord& hit, Color3f& attenuation, Ray3f& scattered) const virtual

Compute the scattered direction scattered at a surface hitpoint.

Parameters
ray in incoming ray
hit in the ray's intersection with the surface
attenuation in how much the light should be attenuated
scattered in the direction light should be scattered
Returns bool True if the surface scatters light

The base Material does not scatter any light, so it simply returns false.

Color3f Material::emitted(const Ray3f& ray, const HitRecord& hit) const virtual

Compute the amount of emitted light at the surface hitpoint.

Parameters
ray in the incoming ray
hit in the ray's intersection with the surface
Returns the emitted color

The base Material class does not emit light, so it simply returns black.

bool Material::sample(const Ray3f& ray, const HitRecord& hit, ScatterRecord& srec, const Vec2f& rv, float rv1) const virtual

Sample a scattered direction at the surface hitpoint hit.

Parameters
ray in The incoming ray (points at surface)
hit in The incoming ray's intersection with the surface
srec out Populate srec.wo, srec.is_specular, and srec.attenuation
rv in A 2D random variables in $[0,1)^2$ to use when generating the sample
rv1 in A 1D random variable in $[0,1)$ to use when generating the sample
Returns bool True if the surface scatters light

If it is not possible to evaluate the pdf of the material (e.g. it is specular or unknown), then set srec.is_specular to true, and populate srec.wo and srec.attenuation just like we did previously in the scatter() function. This allows you to fall back to the way we did things with the scatter() function, i.e. bypassing pdf() evaluations needed for explicit Monte Carlo integration in your #Integrator, but this also precludes the use of MIS or mixture sampling since the pdf is unknown.

Color3f Material::eval(const Ray3f& ray, const Vec3f& scattered, const HitRecord& hit) const virtual

Evaluate the material response for the given pair of directions.

Parameters
ray in The incoming ray (points at surface)
scattered in The outgoing ray direction (points out of surface)
hit in The shading hit point
Returns Color3f The evaluated color

For non-specular materials, this should be the BSDF multiplied by the cosine foreshortening term.

Specular contributions should be excluded.

float Material::pdf(const Ray3f& ray, const Vec3f& scattered, const HitRecord& hit) const virtual

Compute the probability density that sample() will generate scattered (given wi).

Parameters
ray in The incoming ray
scattered in The outgoing ray direction
hit in The shading hit point
Returns float A probability density value in solid angle measure around hit.p.