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Cycles: new Microfacet-based Hair BSDF with elliptical cross-section support #105600

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Weizhen Huang merged 114 commits from weizhen/blender:microfacet_hair into main 2023-08-18 12:46:20 +02:00
Conversation 12 Commits 114 Files Changed 25 +8 -4
1 changed files with 8 additions and 4 deletions
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12
intern/cycles/kernel/closure/bsdf_hair_microfacet.h
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@ -864,16 +864,20 @@ ccl_device void bsdf_microfacet_hair_blur(ccl_private ShaderClosure *sc, float r
bsdf->roughness = fmaxf(roughness, bsdf->roughness);
}
/* Hair Albedo. */
/* Hair Albedo. Computed by summing up geometric series, assuming circular cross-section and
* specular reflection. */
ccl_device Spectrum bsdf_microfacet_hair_albedo(ccl_private const ShaderData *sd,
ccl_private const ShaderClosure *sc)
{
ccl_private MicrofacetHairBSDF *bsdf = (ccl_private MicrofacetHairBSDF *)sc;
const float f = fresnel_dielectric_cos(dot(sd->N, sd->wi), bsdf->eta);
const float3 wmi = make_float3(bsdf->h, 0.0f, cos_from_sin(bsdf->h));
float cos_t;
const float f = fresnel_dielectric(dot(wmi, bsdf->extra->wi), bsdf->eta, &cos_t);
const float3 wt = refract_angle(bsdf->extra->wi, wmi, cos_t, 1.0f / bsdf->eta);
const Spectrum A = exp(2.0f * bsdf->sigma * cos_t / (1.0f - sqr(wt.y)));
return exp(-sqrt(bsdf->sigma) * bsdf_principled_hair_albedo_roughness_scale(bsdf->roughness)) +
make_spectrum(f);
return safe_divide(A - 2.0f * f * A + f, one_spectrum() - f * A);
}
CCL_NAMESPACE_END