area emitter

class area_t : public wt::emitter::emitter_t

An area emitter is attached to a shape, and radiates isotropically from the shape’s surfaces. A texture can be used to spatially module the emitted radiance. Only textures that provide wt::texture::texture_t::mean_spectrum() and wt::texture::texture_t::get_RGBA are supported. For bitmap textures: alpha is ignored. When a texture is used, per-triangle barycentric sampling data for the given texture is constructed. This enables good sampling, but this is an expensive operation and increases loading times.

Public Functions

inline area_t(std::string id, std::shared_ptr<texture::texture_t> radiance, std::shared_ptr<spectrum::spectrum_real_t> average_radiance, f_t scale = 1, f_t emitter_phase_space_extent_scale = 1)

Constructs an area emitter.

Parameters:

  • radiance – (optional) the emission radiance texture; if provided, must be an RGB bitmap texture.

  • average_radiance – average emission spectrum (the radiance texture averaged across the area emitter’s shape). For non-spatially varying area emitters, i.e. when no radiance texture is provided, average_radiance is used for emission.

area_t(const area_t&) = delete
area_t(area_t&&) = default
inline virtual bool is_area_emitter() const noexcept override
inline virtual bool is_delta_position() const noexcept override
inline virtual bool is_delta_direction() const noexcept override
inline spectral_radiance_t spectral_radiance(const intersection_surface_t &surface, const wavenumber_t k) const noexcept
inline virtual const spectrum::spectrum_real_t &emission_spectrum() const noexcept override

Returns the emitter’s average emission spectrum.

inline virtual spectral_radiant_flux_t power(wavenumber_t k) const noexcept override

Computes total emitted spectral power.

inline virtual radiant_flux_t power(const range_t<wavenumber_t> &krange) const noexcept override

Computes total emitted power over a wavenumber range.

inline beam::sourcing_geometry_t sourcing_geometry(const wavenumber_t k) const noexcept
inline spectral_radiance_beam_t Le(const ray_t &r, const wavenumber_t k, const intersection_surface_t *surface) const noexcept

Source a beam from the emitter.

Parameters:

  • r – desired emission phase-space position (ray) on the light source

  • k – wavenumber

  • surface – surface at emission point

virtual spectral_radiant_flux_stokes_t Li(const importance_flux_beam_t &beam, const intersection_surface_t *surface = nullptr) const noexcept override

Integrate a detector beam over the emitter.

Parameters:

beam – detection beam incident upon the emitter

virtual emitter_sample_t sample(sampler::sampler_t &sampler, const wavenumber_t k) const noexcept override

Samples a emission phase-space position (ray) on the light source.

Parameters:

k – wavenumber

virtual position_sample_t sample_position(sampler::sampler_t &sampler) const noexcept override

Samples an emission phase-space position (ray) on the light source.

virtual emitter_direct_sample_t sample_direct(sampler::sampler_t &sampler, const pqvec3_t &wp, const wavenumber_t k) const noexcept override

Samples a direct connection to a world position.

Parameters:

  • wp – world position

  • k – wavenumber

virtual area_sampling_pd_t pdf_position(const pqvec3_t &p, const intersection_surface_t *surface = nullptr) const noexcept override

Sampling PDF of an emission position on the light source.

Parameters:

  • p – position on light source

  • surface – emitter surface intersection record

virtual solid_angle_sampling_pd_t pdf_direction(const pqvec3_t &p, const dir3_t &dir, const intersection_surface_t *surface = nullptr) const noexcept override

Sampling PDF of an emission direction from the light source.

Parameters:

  • p – position on light source

  • dir – emission direction

  • surface – emitter surface intersection record

virtual solid_angle_sampling_pd_t pdf_direct(const pqvec3_t &wp, const ray_t &r, const intersection_surface_t *surface = nullptr) const noexcept override

Sampling PDF of a direct connection.

Parameters:

  • wp – world position from which direct sampling was applied

  • sampled_r – sampled emitter phase-space position (ray)

  • sampled_surface – sampled surface for emitter samples that seat on a surface (required)

Returns:

the solid angle density from wp

virtual scene::element::info_t description() const override

Public Static Functions

static std::unique_ptr<emitter_t> load(std::string id, scene::loader::loader_t *loader, const scene::loader::node_t &node, const wt::wt_context_t &context)

Friends

friend class wt::shape_t