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// Copyright 2009-2021 Intel Corporation
// SPDX-License-Identifier: Apache-2.0
#pragma once
#include "../math/sampling.h"
namespace embree {
/*! \addtogroup rivl_render_embree_ivl */
/*! @{ */
/*! Reflects a viewing vector V at a normal N. */
inline Vec3fa reflect(const Vec3fa& V, const Vec3fa& N) { return 2.0f*dot(V,N)*N-V; }
#ifdef ISPC
inline Vec3fa reflect(const Vec3fa& V, const Vec3fa& N) { return 2.0f*dot(V,N)*N-V; }
inline Vec3fa reflect(const Vec3fa& V, const Vec3fa& N) { return 2.0f*dot(V,N)*N-V; }
inline Vec3fa reflect(const Vec3fa& V, const Vec3fa& N) { return 2.0f*dot(V,N)*N-V; }
#endif
/*! Reflects a viewing vector V at a normal N. Cosine between V
* and N is given as input. */
inline Vec3fa reflect(const Vec3fa &V, const Vec3fa &N, const float cosi) {
return 2.0f*cosi*N-V;
}
// =======================================================
/*!Refracts a viewing vector V at a normal N using the relative
* refraction index eta. Eta is refraction index of outside medium
* (where N points into) divided by refraction index of the inside
* medium. The vectors V and N have to point towards the same side
* of the surface. The cosine between V and N is given as input and
* the cosine of -N and transmission ray is computed as output. */
inline Sample3f refract(const Vec3fa& V, const Vec3fa& N, const float eta,
const float cosi, float &cost)
{
const float k = 1.0f-eta*eta*(1.0f-cosi*cosi);
if (k < 0.0f) { cost = 0.0f; return make_Sample3f(Vec3fa(0.f),0.0f); }
cost = sqrt(k);
return make_Sample3f(eta*(cosi*N-V)-cost*N, sqr(eta));
}
/*! Computes fresnel coefficient for media interface with relative
* refraction index eta. Eta is the outside refraction index
* divided by the inside refraction index. Both cosines have to be
* positive. */
inline float fresnelDielectric(const float cosi, const float cost, const float eta)
{
const float Rper = (eta*cosi - cost) * rcp(eta*cosi + cost);
const float Rpar = ( cosi - eta*cost) * rcp( cosi + eta*cost);
return 0.5f*(Rpar*Rpar + Rper*Rper);
}
/*! Computes fresnel coefficient for media interface with relative
* refraction index eta. Eta is the outside refraction index
* divided by the inside refraction index. The cosine has to be
* positive. */
inline float fresnelDielectric(const float cosi, const float eta)
{
const float k = 1.0f-eta*eta*(1.0f-cosi*cosi);
if (k < 0.0f) return 1.0f;
const float cost = sqrt(k);
return fresnelDielectric(cosi, cost, eta);
}
/*! Computes fresnel coefficient for conductor medium with complex
* refraction index (eta,k). The cosine has to be positive. */
inline Vec3fa fresnelConductor(const float cosi, const Vec3fa& eta, const Vec3fa& k)
{
const Vec3fa tmp = eta*eta + k*k;
const Vec3fa Rpar = (tmp * (cosi*cosi) - 2.0f*eta*cosi + Vec3fa(1.0f)) *
rcp(tmp * (cosi*cosi) + 2.0f*eta*cosi + Vec3fa(1.0f));
const Vec3fa Rper = (tmp - 2.0f*eta*cosi + Vec3fa(cosi*cosi)) *
rcp(tmp + 2.0f*eta*cosi + Vec3fa(cosi*cosi));
return 0.5f * (Rpar + Rper);
}
// =======================================================
struct FresnelConductor {
Vec3fa eta; //!< Real part of refraction index
Vec3fa k; //!< Imaginary part of refraction index
};
inline Vec3fa eval(const FresnelConductor& This, const float cosTheta) {
return fresnelConductor(cosTheta,This.eta,This.k);
}
inline FresnelConductor make_FresnelConductor(const Vec3fa& eta, const Vec3fa& k) {
FresnelConductor m; m.eta = eta; m.k = k; return m;
}
#if defined(ISPC)
inline FresnelConductor make_FresnelConductor(const Vec3fa& eta, const Vec3fa& k) {
FresnelConductor m; m.eta = eta; m.k = k; return m;
}
#endif
// =======================================================
struct FresnelDielectric
{
/*! refraction index of the medium the incident ray travels in */
float etai;
/*! refraction index of the medium the outgoing transmission rays
* travels in */
float etat;
};
inline Vec3fa eval(const FresnelDielectric& This, const float cosTheta) {
return Vec3fa(fresnelDielectric(cosTheta,This.etai/This.etat));
}
inline FresnelDielectric make_FresnelDielectric(const float etai, const float etat) {
FresnelDielectric m; m.etai = etai; m.etat = etat; return m;
}
#if defined(ISPC)
inline FresnelDielectric make_FresnelDielectric(const float etai, const float etat) {
FresnelDielectric m; m.etai = etai; m.etat = etat; return m;
}
#endif
// =======================================================
struct PowerCosineDistribution {
float exp;
};
inline float eval(const PowerCosineDistribution &This, const float cosThetaH) {
return (This.exp+2) * (1.0f/(2.0f*(float(M_PI)))) * pow(abs(cosThetaH), This.exp);
}
#if defined(ISPC)
inline float eval(const PowerCosineDistribution &This, const float cosThetaH) {
return (This.exp+2) * (1.0f/(2.0f*(float(M_PI)))) * pow(abs(cosThetaH), This.exp);
}
#endif
/*! Samples the power cosine distribution. */
inline void sample(const PowerCosineDistribution& This, const Vec3fa& wo, const Vec3fa& N, Sample3f &wi, const Vec2f s)
{
Vec3fa dir = powerCosineSampleHemisphere(This.exp,s);
Sample3f wh;
wh.v = frame(N) * dir;
wh.pdf = powerCosineSampleHemispherePDF(dir,This.exp);
Sample3f r = make_Sample3f(reflect(wo,wh.v),1.0f);
wi = make_Sample3f(r.v,wh.pdf/(4.0f*abs(dot(wo,wh.v))));
}
/*! Samples the power cosine distribution. */
#if defined(ISPC)
inline void sample(const PowerCosineDistribution& This, const Vec3fa& wo, const Vec3fa& N, Sample3f &wi, const Vec2f s)
{
Vec3fa dir = powerCosineSampleHemisphere(This.exp,s);
Sample3f wh;
wh.v = frame(N) * dir;
wh.pdf = powerCosineSampleHemispherePDF(dir,This.exp);
Sample3f r = make_Sample3f(reflect(wo,wh.v),1.0f);
wi = make_Sample3f(r.v,wh.pdf/(4.0f*abs(dot(wo,wh.v))));
}
#endif
inline PowerCosineDistribution make_PowerCosineDistribution(const float _exp) {
PowerCosineDistribution m; m.exp = _exp; return m;
}
#if defined(ISPC)
inline PowerCosineDistribution make_PowerCosineDistribution(const float _exp) {
PowerCosineDistribution m; m.exp = _exp; return m;
}
#endif
} // namespace embree
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