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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 +28 -18
1 changed files with 28 additions and 18 deletions
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46
intern/cycles/kernel/closure/bsdf_hair_microfacet.h
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@ -268,6 +268,14 @@ ccl_device_inline bool microfacet_visible(const float3 wi,
return microfacet_visible(wi, m, h) && microfacet_visible(wo, m, h);
}
template<MicrofacetType m_type>
ccl_device_inline float bsdf_Go(float alpha2, float cos_NI, float cos_NO)
{
const float lambdaI = bsdf_lambda<m_type>(alpha2, cos_NI);
const float lambdaO = bsdf_lambda<m_type>(alpha2, cos_NO);
return (1.0f + lambdaI) / (1.0f + lambdaI + lambdaO);
}
/* Compute fresnel reflection. Also return the dot product of the refracted ray and the normal as
* `cos_theta_t`, as it is used when computing the direction of the refracted ray. */
ccl_device float fresnel(float cos_theta_i, float eta, ccl_private float *cos_theta_t)
@ -392,9 +400,8 @@ ccl_device Spectrum bsdf_microfacet_hair_eval_r(ccl_private const ShaderClosure
if (microfacet_visible(wi, wo, make_float3(wm.x, 0.0f, wm.z), wh)) {
const float weight = (i == 0 || i == intervals) ? 0.5f : (i % 2 + 1);
/* NOTE: using separable masking and shadowing as one factor cancels out in `sample()`. */
const float G = bsdf_G<m_type>(roughness2, dot(wm, wi)) *
bsdf_G<m_type>(roughness2, dot(wm, wo));
const float cos_mi = dot(wm, wi);
const float G = bsdf_G<m_type>(roughness2, cos_mi, dot(wm, wo));
integral += weight * bsdf_D<m_type>(roughness2, dot(wm, wh)) * G *
arc_length(bsdf->extra->e2, gamma_m);
}
@ -490,7 +497,7 @@ ccl_device Spectrum bsdf_microfacet_hair_eval_tt_trt(KernelGlobals kg,
const float cos_mi1 = dot(wi, wmi);
const float cos_mo1 = dot(-wt, wmi);
const float cos_mi2 = dot(-wt, wmt);
const float G1o = bsdf_G<m_type>(roughness2, cos_mo1);
const float G1o = bsdf_Go<m_type>(roughness2, cos_mi1, cos_mo1);
if (!microfacet_visible(wi, -wt, wmi, wh1) || !microfacet_visible(wi, -wt, wmi_, wh1)) {
continue;
}
@ -516,8 +523,7 @@ ccl_device Spectrum bsdf_microfacet_hair_eval_tt_trt(KernelGlobals kg,
const float T2 = 1.0f - fresnel_dielectric_cos(cos_hi2, inv_eta);
const float D2 = bsdf_D<m_type>(roughness2, cos_mh2);
const float G2 = bsdf_G<m_type>(roughness2, cos_mi2) *
bsdf_G<m_type>(roughness2, cos_mo2);
const float G2 = bsdf_G<m_type>(roughness2, cos_mi2, cos_mo2);
const Spectrum result = weight * T1 * T2 * D2 * G1o * G2 * A_t / cos_mo1 * cos_mi1 *
cos_hi2 * cos_ho2 * sqr(rcp_norm_wh2);
@ -577,9 +583,9 @@ ccl_device Spectrum bsdf_microfacet_hair_eval_tt_trt(KernelGlobals kg,
-len(to_point(gamma_mtr, b) - to_point(gamma_mt, b))));
const float cos_mo2 = dot(wmt, -wtr);
const float G2o = bsdf_G<m_type>(roughness2, cos_mo2);
const float G3 = bsdf_G<m_type>(roughness2, dot(wmtr, wtr)) *
bsdf_G<m_type>(roughness2, dot(wmtr, -wo));
const float G2o = bsdf_Go<m_type>(roughness2, cos_mi2, cos_mo2);
const float cos_mi3 = dot(wmtr, wtr);
const float G3 = bsdf_G<m_type>(roughness2, cos_mi3, dot(wmtr, -wo));
const Spectrum result = weight * T1 * R2 * T3 * D3 * G1o * G2o * G3 * A_t * A_tr /
(cos_mo1 * cos_mo2) * cos_mi1 * cos_mi2 * cos_hi3 * cos_ho3 *
@ -660,8 +666,9 @@ ccl_device int bsdf_microfacet_hair_sample(const KernelGlobals kg,
float st, ct;
fast_sincosf(bsdf->tilt, &st, &ct);
const float3 wmi = make_float3(wmi_.x * ct, st, wmi_.z * ct);
const float cos_mi1 = dot(wmi, wi);
if (dot(wmi, wi) < 0.0f || dot(wmi_, wi) < 0.0f) {
if (cos_mi1 < 0.0f || dot(wmi_, wi) < 0.0f) {
/* Macro/mesonormal invisible. */
*pdf = 0.0f;
return LABEL_NONE;
@ -698,8 +705,10 @@ ccl_device int bsdf_microfacet_hair_sample(const KernelGlobals kg,
float3 wh3, wtt, wtrt, wmtr;
Spectrum TT = zero_spectrum();
Spectrum TRT = zero_spectrum();
const float cos_mi2 = dot(-wt, wmt);
float cos_mi3;
if (dot(wh2, -wt) > 0.0f && dot(wmt, -wt) > 0.0f && microfacet_visible(-wt, -wtr, wmt_, wh2)) {
if (dot(wh2, -wt) > 0.0f && cos_mi2 > 0.0f && microfacet_visible(-wt, -wtr, wmt_, wh2)) {
const Spectrum mu_a = bsdf->sigma;
const Spectrum A_t = exp(mu_a / cos_theta(wt) *
(is_circular ?
@ -729,7 +738,8 @@ ccl_device int bsdf_microfacet_hair_sample(const KernelGlobals kg,
wtrt = -refract_angle(wtr, wh3, cos_theta_t3, *eta);
if (cos_theta_t3 != 0.0f && dot(wtr, wh3) > 0.0f && dot(wmtr, wtr) > 0.0f &&
cos_mi3 = dot(wmtr, wtr);
if (cos_theta_t3 != 0.0f && dot(wtr, wh3) > 0.0f && cos_mi3 > 0.0f &&
dot(wmtr, -wtrt) > 0.0f &&
microfacet_visible(wtr, -wtrt, make_float3(wmtr.x, 0.0f, wmtr.z), wh3)) {
const Spectrum T3 = make_spectrum(1.0f - R3);
@ -764,7 +774,7 @@ ccl_device int bsdf_microfacet_hair_sample(const KernelGlobals kg,
*eval = R / r * total_energy;
Lukas Stockner commented 2023-08-07 01:15:50 +02:00
Outdated
Review
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I think this is only used if we actually sample TRRT? The compiler should probably optimize that by itself though I guess.

I think this is only used if we actually sample TRRT? The compiler should probably optimize that by itself though I guess.
if (microfacet_visible(wi, wr, wmi_, wh1)) {
visibility = bsdf_G<m_type>(roughness2, dot(wmi, wr));
visibility = bsdf_Go<m_type>(roughness2, cos_mi1, dot(wmi, wr));
}
}
else if (sample_lobe < (r + tt)) {
@ -772,8 +782,8 @@ ccl_device int bsdf_microfacet_hair_sample(const KernelGlobals kg,
*eval = TT / tt * total_energy;
if (microfacet_visible(wi, -wt, wmi_, wh1) && microfacet_visible(-wt, -wtt, wmt_, wh2)) {
visibility = bsdf_G<m_type>(roughness2, dot(wmi, -wt)) *
bsdf_G<m_type>(roughness2, dot(wmt, -wtt));
visibility = bsdf_Go<m_type>(roughness2, cos_mi1, dot(wmi, -wt)) *
bsdf_Go<m_type>(roughness2, cos_mi2, dot(wmt, -wtt));
}
}
else { /* if (sample_lobe >= (r + tt)) */
@ -781,9 +791,9 @@ ccl_device int bsdf_microfacet_hair_sample(const KernelGlobals kg,
*eval = TRT / trt * total_energy;
if (microfacet_visible(wi, -wt, wmi_, wh1)) {
visibility = bsdf_G<m_type>(roughness2, dot(wmi, -wt)) *
bsdf_G<m_type>(roughness2, dot(wmt, -wtr)) *
bsdf_G<m_type>(roughness2, dot(wmtr, -wtrt));
visibility = bsdf_Go<m_type>(roughness2, cos_mi1, dot(wmi, -wt)) *
bsdf_Go<m_type>(roughness2, cos_mi2, dot(wmt, -wtr)) *
bsdf_Go<m_type>(roughness2, cos_mi3, dot(wmtr, -wtrt));
}
}
label |= LABEL_REFLECT;