BSDF

Detailed Description

This module defines the Bidirectional Scattering Distribution Function employed throughout Fermat. At present time, this model is rather simple, and consists of four layered components only:

• a diffuse reflection component
• a diffuse transmission component
• a glossy reflection component layered on top of the diffuse layer
• a glossy transmission component layered on top of the diffuse layer

The diffuse model is purely Lambertian, while the glossy components are based on the GGX model with Smith's joint masking-shadowing function described in:

[Heitz 2014, "Understanding the Masking-Shadowing Function in Microfacet-Based BRDFs"]

Classes
struct	Bsdf
struct	Edf
struct	cugar::BlendBsdf< TBsdf1, TBsdf2 >
struct	cugar::DifferentialGeometry
struct	cugar::GGXVCavityMicrofacetDistribution
struct	cugar::GGXBsdf
struct	cugar::GGXSmithMicrofacetDistribution
struct	cugar::GGXSmithBsdf
struct	cugar::LambertBsdf
struct	cugar::LambertEdf
struct	cugar::LambertTransBsdf
struct	cugar::LTCBsdf

Enumerations
enum	TransportType { kRadianceTransport = 0, kParticleTransport = 1 }
enum	cugar::SphericalMeasure { kSolidAngle = 0, kProjectedSolidAngle = 1 }

Functions
FERMAT_API void	precompute_glossy_reflectance (const uint32 S, float *tables)
FERMAT_API void	precompute_TIR_loss (const uint32 S, float *tables)
bool	cugar::bsdf_test (uint32 test_index, const GGXSmithBsdf &bsdf)
bool	cugar::bsdf_test ()
CUGAR_FORCEINLINE CUGAR_HOST_DEVICE Vector3f	cugar::microfacet (const Vector3f V, const Vector3f L, const Vector3f N, const float inv_eta)
CUGAR_FORCEINLINE CUGAR_HOST_DEVICE Vector3f	cugar::vndf_microfacet (const Vector3f V, const Vector3f L, const Vector3f N, const float inv_eta)
CUGAR_FORCEINLINE CUGAR_HOST_DEVICE float	cugar::hvd_ggx_eval (const float2 &inv_alpha, const float nh, const float ht, const float hb)
CUGAR_FORCEINLINE CUGAR_HOST_DEVICE float3	cugar::hvd_ggx_sample (const float2 &samples, const float inv_alpha)
CUGAR_FORCEINLINE CUGAR_HOST_DEVICE float3	cugar::hvd_ggx_sample (const float2 &samples, const float2 &inv_alpha)
CUGAR_FORCEINLINE CUGAR_HOST_DEVICE float2	cugar::hvd_ggx_invert (const float3 H, const float2 inv_alpha)
CUGAR_FORCEINLINE CUGAR_HOST_DEVICE float3	cugar::vndf_ggx_smith_sample (const float2 samples, const float2 alpha, const Vector3f _V)
CUGAR_FORCEINLINE CUGAR_HOST_DEVICE float2	cugar::vndf_ggx_smith_invert (const Vector3f _N, const float2 alpha, const Vector3f _V)
CUGAR_FORCEINLINE CUGAR_HOST_DEVICE uint32	cugar::clip_quad_to_horizon (cugar::Vector3f L[5])
template<typename VectorType >
CUGAR_FORCEINLINE CUGAR_HOST_DEVICE VectorType	cugar::fresnel_dielectric (const float cos_theta_i, const float cos_theta_t, const VectorType eta)
template<typename VectorType >
CUGAR_HOST_DEVICE CUGAR_FORCEINLINE VectorType	cugar::fresnel_dielectric_conductor (const float cos_theta, const VectorType eta, const VectorType eta_k)
CUGAR_HOST_DEVICE CUGAR_FORCEINLINE float	cugar::pow5 (const float x)
template<typename VectorType >
CUGAR_FORCEINLINE CUGAR_HOST_DEVICE VectorType	cugar::fresnel_schlick (float cos_theta_i, const float eta, const VectorType fresnel_base)
CUGAR_FORCEINLINE CUGAR_HOST_DEVICE bool	cugar::refraction_angle (const Vector3f w_i, const Vector3f N, const float eta, const float cos_theta_i, float *cos_theta_t)
CUGAR_FORCEINLINE CUGAR_HOST_DEVICE bool	cugar::refract (const Vector3f w_i, const Vector3f N, const float cos_theta_i, const float eta, Vector3f *out, float *F)
CUGAR_FORCEINLINE CUGAR_HOST_DEVICE Vector3f	cugar::refract (const Vector3f w_i, const Vector3f N, const float eta, const float cos_theta_i, const float cos_theta_t)

Enumeration Type Documentation

SphericalMeasure

enum cugar::SphericalMeasure

Spherical measure type

TransportType

enum TransportType

transport type: defines whether we are tracing rays, or particles, i.e. whether the quantity being transported is radiance or power.

Function Documentation

bsdf_test()

bool cugar::bsdf_test ( )

inline

unit test

clip_quad_to_horizon()

CUGAR_FORCEINLINE CUGAR_HOST_DEVICE uint32 cugar::clip_quad_to_horizon

(

cugar::Vector3f

L[5]

)

clip a quad to the plane z = 0

fresnel_dielectric()

template<typename VectorType >

CUGAR_FORCEINLINE CUGAR_HOST_DEVICE VectorType cugar::fresnel_dielectric	(	const float	cos_theta_i,
		const float	cos_theta_t,
		const VectorType	eta
	)

Evaluate the Fresnel reflection coefficient for dielectrics

fresnel_dielectric_conductor()

template<typename VectorType >

CUGAR_HOST_DEVICE CUGAR_FORCEINLINE VectorType cugar::fresnel_dielectric_conductor	(	const float	cos_theta,
		const VectorType	eta,
		const VectorType	eta_k
	)

Evaluate the Fresnel reflection coefficient for dielectric/conductor interfaces

fresnel_schlick()

template<typename VectorType >

CUGAR_FORCEINLINE CUGAR_HOST_DEVICE VectorType cugar::fresnel_schlick	(	float	cos_theta_i,
		const float	eta,
		const VectorType	fresnel_base
	)

Evaluate the Fresnel reflection coefficient using Schlick's approximation

Parameters

eta	incoming IOR / outgoing IOR

hvd_ggx_eval()

CUGAR_FORCEINLINE CUGAR_HOST_DEVICE float cugar::hvd_ggx_eval	(	const float2 &	inv_alpha,
		const float	nh,
		const float	ht,
		const float	hb
	)

evaluate anisotropic GGX / Trowbridge-Reitz distribution on the non-projected hemisphere

[Walter et al. 2007, "Microfacet models for refraction through rough surfaces"]

nh

hvd_ggx_invert()

CUGAR_FORCEINLINE CUGAR_HOST_DEVICE float2 cugar::hvd_ggx_invert	(	const float3	H,
		const float2	inv_alpha
	)

invert the the half-vector anisotropic GGX distribution sampling function

hvd_ggx_sample() [1/2]

CUGAR_FORCEINLINE CUGAR_HOST_DEVICE float3 cugar::hvd_ggx_sample	(	const float2 &	samples,
		const float	inv_alpha
	)

sample isotropic GGX distribution on the non-projected hemisphere

hvd_ggx_sample() [2/2]

CUGAR_FORCEINLINE CUGAR_HOST_DEVICE float3 cugar::hvd_ggx_sample	(	const float2 &	samples,
		const float2 &	inv_alpha
	)

sample the half-vector anisotropic GGX distribution on the non-projected hemisphere

microfacet()

CUGAR_FORCEINLINE CUGAR_HOST_DEVICE Vector3f cugar::microfacet	(	const Vector3f	V,
		const Vector3f	L,
		const Vector3f	N,
		const float	inv_eta
	)

return the microfacet normal for a given pair of incident and outgoing direction vectors

refract() [1/2]

CUGAR_FORCEINLINE CUGAR_HOST_DEVICE bool cugar::refract	(	const Vector3f	w_i,
		const Vector3f	N,
		const float	cos_theta_i,
		const float	eta,
		Vector3f *	out,
		float *	F
	)

Evaluate refraction; this function returns false upon Total Internal Reflection (TIR).

refract() [2/2]

CUGAR_FORCEINLINE CUGAR_HOST_DEVICE Vector3f cugar::refract	(	const Vector3f	w_i,
		const Vector3f	N,
		const float	eta,
		const float	cos_theta_i,
		const float	cos_theta_t
	)

Evaluate refraction given the incident and transmitted angles with the normal

refraction_angle()

CUGAR_FORCEINLINE CUGAR_HOST_DEVICE bool cugar::refraction_angle	(	const Vector3f	w_i,
		const Vector3f	N,
		const float	eta,
		const float	cos_theta_i,
		float *	cos_theta_t
	)

Evaluate the cosine of the refraction angle with the normal - cos(theta_t)

vndf_ggx_smith_invert()

CUGAR_FORCEINLINE CUGAR_HOST_DEVICE float2 cugar::vndf_ggx_smith_invert	(	const Vector3f	_N,
		const float2	alpha,
		const Vector3f	_V
	)

Inversion function for "A Simpler and Exact Sampling Routine for the GGX Distribution of Visible Normals" https://hal.archives-ouvertes.fr/hal-01509746

vndf_ggx_smith_sample()

CUGAR_FORCEINLINE CUGAR_HOST_DEVICE float3 cugar::vndf_ggx_smith_sample	(	const float2	samples,
		const float2	alpha,
		const Vector3f	_V
	)

A Simpler and Exact Sampling Routine for the GGX Distribution of Visible Normals https://hal.archives-ouvertes.fr/hal-01509746

vndf_microfacet()

CUGAR_FORCEINLINE CUGAR_HOST_DEVICE Vector3f cugar::vndf_microfacet	(	const Vector3f	V,
		const Vector3f	L,
		const Vector3f	N,
		const float	inv_eta
	)

return the microfacet normal for a given pair of incident and outgoing direction vectors