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e9151dc96a2abcfd31b69c376db981f97d3e3c6a
blender-archive/intern/cycles/kernel/closure/bsdf_microfacet_multi.h
Lukas Stockner 73000c792d Cycles: Reorganize Fresnel handling in Microfacet closures 
This is both a cleanup and a preparation for the Principled v2 changes.
Notable changes:
- Clearcoat weight is now folded into the closure weight, there's no reason
  to track this separately.
- There's a general-purpose helper for computing a Closure's albedo, which is
  currently used by the denoising albedo and diffuse/gloss/transmission color
  passes.
- The d/g/t color passes didn't account for closure albedo before, this means
  that e.g. metallic shaders with Principled v2 now have their color texture
  included in the glossy color pass. Also fixes T104041 (sheen albedo).
- Instead of precomputing and storing the albedo during shader setup, compute
  it when needed. This is technically redundant since we still need to compute
  it on shader setup to adjust the sample weight, but the operation is cheap
  enough that freeing up the storage seems worth it.
- Future changes (Principled v2) are easier to integrate since the Fresnel
  handling isn't all over the place anymore.
- Fresnel handling in the Multiscattering GGX code is still ugly, but since
  removing that entirely is the next step, putting effort into cleaning it up
  doesn't seem worth it.
- Apart from the d/g/t color passes, no changes to render results are expected.

Differential Revision: https://developer.blender.org/D17101
2023-02-03 21:03:48 +01:00

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/* SPDX-License-Identifier: Apache-2.0
* Copyright 2011-2022 Blender Foundation */
#pragma once
#include "kernel/sample/lcg.h"
#include "kernel/sample/mapping.h"
CCL_NAMESPACE_BEGIN
/* Most of the code is based on the supplemental implementations from
* https://eheitzresearch.wordpress.com/240-2/. */
/* === GGX Microfacet distribution functions === */
/* Isotropic GGX microfacet distribution */
ccl_device_forceinline float D_ggx(float3 wm, float alpha)
{
wm.z *= wm.z;
alpha *= alpha;
float tmp = (1.0f - wm.z) + alpha * wm.z;
return alpha / max(M_PI_F * tmp * tmp, 1e-7f);
}
/* Anisotropic GGX microfacet distribution */
ccl_device_forceinline float D_ggx_aniso(const float3 wm, const float2 alpha)
{
float slope_x = -wm.x / alpha.x;
float slope_y = -wm.y / alpha.y;
float tmp = wm.z * wm.z + slope_x * slope_x + slope_y * slope_y;
return 1.0f / max(M_PI_F * tmp * tmp * alpha.x * alpha.y, 1e-7f);
}
/* Sample slope distribution (based on page 14 of the supplemental implementation). */
ccl_device_forceinline float2 mf_sampleP22_11(const float cosI,
const float randx,
const float randy)
{
if (cosI > 0.9999f || fabsf(cosI) < 1e-6f) {
const float r = sqrtf(randx / max(1.0f - randx, 1e-7f));
const float phi = M_2PI_F * randy;
return make_float2(r * cosf(phi), r * sinf(phi));
}
const float sinI = sin_from_cos(cosI);
const float tanI = sinI / cosI;
const float projA = 0.5f * (cosI + 1.0f);
if (projA < 0.0001f)
return make_float2(0.0f, 0.0f);
const float A = 2.0f * randx * projA / cosI - 1.0f;
float tmp = A * A - 1.0f;
if (fabsf(tmp) < 1e-7f)
return make_float2(0.0f, 0.0f);
tmp = 1.0f / tmp;
const float D = safe_sqrtf(tanI * tanI * tmp * tmp - (A * A - tanI * tanI) * tmp);
const float slopeX2 = tanI * tmp + D;
const float slopeX = (A < 0.0f || slopeX2 > 1.0f / tanI) ? (tanI * tmp - D) : slopeX2;
float U2;
if (randy >= 0.5f)
U2 = 2.0f * (randy - 0.5f);
else
U2 = 2.0f * (0.5f - randy);
const float z = (U2 * (U2 * (U2 * 0.27385f - 0.73369f) + 0.46341f)) /
(U2 * (U2 * (U2 * 0.093073f + 0.309420f) - 1.0f) + 0.597999f);
const float slopeY = z * sqrtf(1.0f + slopeX * slopeX);
if (randy >= 0.5f)
return make_float2(slopeX, slopeY);
else
return make_float2(slopeX, -slopeY);
}
/* Visible normal sampling for the GGX distribution
* (based on page 7 of the supplemental implementation). */
ccl_device_forceinline float3 mf_sample_vndf(const float3 wi,
const float2 alpha,
const float randx,
const float randy)
{
const float3 wi_11 = normalize(make_float3(alpha.x * wi.x, alpha.y * wi.y, wi.z));
const float2 slope_11 = mf_sampleP22_11(wi_11.z, randx, randy);
const float3 cossin_phi = safe_normalize(make_float3(wi_11.x, wi_11.y, 0.0f));
const float slope_x = alpha.x * (cossin_phi.x * slope_11.x - cossin_phi.y * slope_11.y);
const float slope_y = alpha.y * (cossin_phi.y * slope_11.x + cossin_phi.x * slope_11.y);
kernel_assert(isfinite(slope_x));
return normalize(make_float3(-slope_x, -slope_y, 1.0f));
}
/* === Phase functions: Glossy and Glass === */
/* Phase function for reflective materials. */
ccl_device_forceinline float3 mf_sample_phase_glossy(const float3 wi,
ccl_private Spectrum *weight,
const float3 wm)
{
return -wi + 2.0f * wm * dot(wi, wm);
}
ccl_device_forceinline Spectrum mf_eval_phase_glossy(const float3 w,
const float lambda,
const float3 wo,
const float2 alpha)
{
if (w.z > 0.9999f)
return zero_spectrum();
const float3 wh = normalize(wo - w);
if (wh.z < 0.0f)
return zero_spectrum();
float pArea = (w.z < -0.9999f) ? 1.0f : lambda * w.z;
const float dotW_WH = dot(-w, wh);
if (dotW_WH < 0.0f)
return zero_spectrum();
float phase = max(0.0f, dotW_WH) * 0.25f / max(pArea * dotW_WH, 1e-7f);
if (alpha.x == alpha.y)
phase *= D_ggx(wh, alpha.x);
else
phase *= D_ggx_aniso(wh, alpha);
return make_spectrum(phase);
}
/* Phase function for dielectric transmissive materials, including both reflection and refraction
* according to the dielectric fresnel term. */
ccl_device_forceinline float3 mf_sample_phase_glass(const float3 wi,
const float eta,
const float3 wm,
const float randV,
ccl_private bool *outside)
{
float cosI = dot(wi, wm);
float f = fresnel_dielectric_cos(cosI, eta);
if (randV < f) {
*outside = true;
return -wi + 2.0f * wm * cosI;
}
*outside = false;
float inv_eta = 1.0f / eta;
float cosT = -safe_sqrtf(1.0f - (1.0f - cosI * cosI) * inv_eta * inv_eta);
return normalize(wm * (cosI * inv_eta + cosT) - wi * inv_eta);
}
ccl_device_forceinline Spectrum mf_eval_phase_glass(const float3 w,
const float lambda,
const float3 wo,
const bool wo_outside,
const float2 alpha,
const float eta)
{
if (w.z > 0.9999f)
return zero_spectrum();
float pArea = (w.z < -0.9999f) ? 1.0f : lambda * w.z;
float v;
if (wo_outside) {
const float3 wh = normalize(wo - w);
if (wh.z < 0.0f)
return zero_spectrum();
const float dotW_WH = dot(-w, wh);
v = fresnel_dielectric_cos(dotW_WH, eta) * max(0.0f, dotW_WH) * D_ggx(wh, alpha.x) * 0.25f /
(pArea * dotW_WH);
}
else {
float3 wh = normalize(wo * eta - w);
if (wh.z < 0.0f)
wh = -wh;
const float dotW_WH = dot(-w, wh), dotWO_WH = dot(wo, wh);
if (dotW_WH < 0.0f)
return zero_spectrum();
float temp = dotW_WH + eta * dotWO_WH;
v = (1.0f - fresnel_dielectric_cos(dotW_WH, eta)) * max(0.0f, dotW_WH) * max(0.0f, -dotWO_WH) *
D_ggx(wh, alpha.x) / (pArea * temp * temp);
}
return make_spectrum(v);
}
/* === Utility functions for the random walks === */
/* Smith Lambda function for GGX (based on page 12 of the supplemental implementation). */
ccl_device_forceinline float mf_lambda(const float3 w, const float2 alpha)
{
if (w.z > 0.9999f)
return 0.0f;
else if (w.z < -0.9999f)
return -0.9999f;
const float inv_wz2 = 1.0f / max(w.z * w.z, 1e-7f);
const float2 wa = make_float2(w.x, w.y) * alpha;
float v = sqrtf(1.0f + dot(wa, wa) * inv_wz2);
if (w.z <= 0.0f)
v = -v;
return 0.5f * (v - 1.0f);
}
/* Height distribution CDF (based on page 4 of the supplemental implementation). */
ccl_device_forceinline float mf_invC1(const float h)
{
return 2.0f * saturatef(h) - 1.0f;
}
ccl_device_forceinline float mf_C1(const float h)
{
return saturatef(0.5f * (h + 1.0f));
}
/* Masking function (based on page 16 of the supplemental implementation). */
ccl_device_forceinline float mf_G1(const float3 w, const float C1, const float lambda)
{
if (w.z > 0.9999f)
return 1.0f;
if (w.z < 1e-5f)
return 0.0f;
return powf(C1, lambda);
}
/* Sampling from the visible height distribution (based on page 17 of the supplemental
* implementation). */
ccl_device_forceinline bool mf_sample_height(const float3 w,
ccl_private float *h,
ccl_private float *C1,
ccl_private float *G1,
ccl_private float *lambda,
const float U)
{
if (w.z > 0.9999f)
return false;
if (w.z < -0.9999f) {
*C1 *= U;
*h = mf_invC1(*C1);
*G1 = mf_G1(w, *C1, *lambda);
}
else if (fabsf(w.z) >= 0.0001f) {
if (U > 1.0f - *G1)
return false;
if (*lambda >= 0.0f) {
*C1 = 1.0f;
}
else {
*C1 *= powf(1.0f - U, -1.0f / *lambda);
}
*h = mf_invC1(*C1);
*G1 = mf_G1(w, *C1, *lambda);
}
return true;
}
/* === PDF approximations for the different phase functions. ===
* As explained in bsdf_microfacet_multi_impl.h, using approximations with MIS still produces an
* unbiased result. */
/* Approximation for the albedo of the single-scattering GGX distribution,
* the missing energy is then approximated as a diffuse reflection for the PDF. */
ccl_device_forceinline float mf_ggx_albedo(float r)
{
float albedo = 0.806495f * expf(-1.98712f * r * r) + 0.199531f;
albedo -= ((((((1.76741f * r - 8.43891f) * r + 15.784f) * r - 14.398f) * r + 6.45221f) * r -
1.19722f) *
r +
0.027803f) *
r +
0.00568739f;
return saturatef(albedo);
}
ccl_device_inline float mf_ggx_transmission_albedo(float a, float ior)
{
if (ior < 1.0f) {
ior = 1.0f / ior;
}
a = saturatef(a);
ior = clamp(ior, 1.0f, 3.0f);
float I_1 = 0.0476898f * expf(-0.978352f * (ior - 0.65657f) * (ior - 0.65657f)) -
0.033756f * ior + 0.993261f;
float R_1 = (((0.116991f * a - 0.270369f) * a + 0.0501366f) * a - 0.00411511f) * a + 1.00008f;
float I_2 = (((-2.08704f * ior + 26.3298f) * ior - 127.906f) * ior + 292.958f) * ior - 287.946f +
199.803f / (ior * ior) - 101.668f / (ior * ior * ior);
float R_2 = ((((5.3725f * a - 24.9307f) * a + 22.7437f) * a - 3.40751f) * a + 0.0986325f) * a +
0.00493504f;
return saturatef(1.0f + I_2 * R_2 * 0.0019127f - (1.0f - I_1) * (1.0f - R_1) * 9.3205f);
}
ccl_device_forceinline float mf_ggx_pdf(const float3 wi, const float3 wo, const float alpha)
{
float D = D_ggx(normalize(wi + wo), alpha);
float lambda = mf_lambda(wi, make_float2(alpha, alpha));
float singlescatter = 0.25f * D / max((1.0f + lambda) * wi.z, 1e-7f);
float multiscatter = wo.z * M_1_PI_F;
float albedo = mf_ggx_albedo(alpha);
return albedo * singlescatter + (1.0f - albedo) * multiscatter;
}
ccl_device_forceinline float mf_ggx_aniso_pdf(const float3 wi, const float3 wo, const float2 alpha)
{
float D = D_ggx_aniso(normalize(wi + wo), alpha);
float lambda = mf_lambda(wi, alpha);
float singlescatter = 0.25f * D / max((1.0f + lambda) * wi.z, 1e-7f);
float multiscatter = wo.z * M_1_PI_F;
float albedo = mf_ggx_albedo(sqrtf(alpha.x * alpha.y));
return albedo * singlescatter + (1.0f - albedo) * multiscatter;
}
ccl_device_forceinline float mf_glass_pdf(const float3 wi,
const float3 wo,
const float alpha,
const float eta)
{
bool reflective = (wi.z * wo.z > 0.0f);
float wh_len;
float3 wh = normalize_len(wi + (reflective ? wo : (wo * eta)), &wh_len);
if (wh.z < 0.0f)
wh = -wh;
float3 r_wi = (wi.z < 0.0f) ? -wi : wi;
float lambda = mf_lambda(r_wi, make_float2(alpha, alpha));
float D = D_ggx(wh, alpha);
float fresnel = fresnel_dielectric_cos(dot(r_wi, wh), eta);
float multiscatter = fabsf(wo.z * M_1_PI_F);
if (reflective) {
float singlescatter = 0.25f * D / max((1.0f + lambda) * r_wi.z, 1e-7f);
float albedo = mf_ggx_albedo(alpha);
return fresnel * (albedo * singlescatter + (1.0f - albedo) * multiscatter);
}
else {
float singlescatter = fabsf(dot(r_wi, wh) * dot(wo, wh) * D * eta * eta /
max((1.0f + lambda) * r_wi.z * wh_len * wh_len, 1e-7f));
float albedo = mf_ggx_transmission_albedo(alpha, eta);
return (1.0f - fresnel) * (albedo * singlescatter + (1.0f - albedo) * multiscatter);
}
}
/* === Actual random walk implementations === */
/* One version of mf_eval and mf_sample per phase function. */
#define MF_NAME_JOIN(x, y) x##_##y
#define MF_NAME_EVAL(x, y) MF_NAME_JOIN(x, y)
#define MF_FUNCTION_FULL_NAME(prefix) MF_NAME_EVAL(prefix, MF_PHASE_FUNCTION)
#define MF_PHASE_FUNCTION glass
#define MF_MULTI_GLASS
#include "kernel/closure/bsdf_microfacet_multi_impl.h"
#define MF_PHASE_FUNCTION glossy
#define MF_MULTI_GLOSSY
#include "kernel/closure/bsdf_microfacet_multi_impl.h"
ccl_device void bsdf_microfacet_multi_ggx_blur(ccl_private ShaderClosure *sc, float roughness)
{
ccl_private MicrofacetBsdf *bsdf = (ccl_private MicrofacetBsdf *)sc;
bsdf->alpha_x = fmaxf(roughness, bsdf->alpha_x);
bsdf->alpha_y = fmaxf(roughness, bsdf->alpha_y);
}
/* === Closure implementations === */
/* Multi-scattering GGX Glossy closure */
ccl_device int bsdf_microfacet_multi_ggx_common_setup(ccl_private MicrofacetBsdf *bsdf)
{
bsdf->alpha_x = clamp(bsdf->alpha_x, 1e-4f, 1.0f);
bsdf->alpha_y = clamp(bsdf->alpha_y, 1e-4f, 1.0f);
bsdf->extra->color = saturate(bsdf->extra->color);
bsdf->extra->cspec0 = saturate(bsdf->extra->cspec0);
return SD_BSDF | SD_BSDF_HAS_EVAL | SD_BSDF_NEEDS_LCG;
}
ccl_device int bsdf_microfacet_multi_ggx_setup(ccl_private MicrofacetBsdf *bsdf)
{
if (is_zero(bsdf->T))
bsdf->T = make_float3(1.0f, 0.0f, 0.0f);
bsdf->type = CLOSURE_BSDF_MICROFACET_MULTI_GGX_ID;
return bsdf_microfacet_multi_ggx_common_setup(bsdf);
}
ccl_device int bsdf_microfacet_multi_ggx_fresnel_setup(ccl_private MicrofacetBsdf *bsdf,
ccl_private const ShaderData *sd)
{
if (is_zero(bsdf->T))
bsdf->T = make_float3(1.0f, 0.0f, 0.0f);
bsdf->type = CLOSURE_BSDF_MICROFACET_MULTI_GGX_FRESNEL_ID;
bsdf_microfacet_adjust_weight(sd, bsdf);
return bsdf_microfacet_multi_ggx_common_setup(bsdf);
}
ccl_device int bsdf_microfacet_multi_ggx_refraction_setup(ccl_private MicrofacetBsdf *bsdf)
{
bsdf->alpha_y = bsdf->alpha_x;
bsdf->type = CLOSURE_BSDF_MICROFACET_MULTI_GGX_ID;
return bsdf_microfacet_multi_ggx_common_setup(bsdf);
}
ccl_device Spectrum bsdf_microfacet_multi_ggx_eval(ccl_private const ShaderClosure *sc,
const float3 Ng,
const float3 wi,
const float3 wo,
ccl_private float *pdf,
ccl_private uint *lcg_state)
{
ccl_private const MicrofacetBsdf *bsdf = (ccl_private const MicrofacetBsdf *)sc;
const float cosNgO = dot(Ng, wo);
if ((cosNgO < 0.0f) || bsdf->alpha_x * bsdf->alpha_y < 1e-7f) {
*pdf = 0.0f;
return zero_spectrum();
}
float3 X, Y, Z;
Z = bsdf->N;
/* Ensure that the both directions are on the outside w.r.t. the shading normal. */
if (dot(Z, wi) <= 0.0f || dot(Z, wo) <= 0.0f) {
*pdf = 0.0f;
return zero_spectrum();
}
bool use_fresnel = (bsdf->type == CLOSURE_BSDF_MICROFACET_MULTI_GGX_FRESNEL_ID);
bool is_aniso = (bsdf->alpha_x != bsdf->alpha_y);
if (is_aniso)
make_orthonormals_tangent(Z, bsdf->T, &X, &Y);
else
make_orthonormals(Z, &X, &Y);
float3 local_I = make_float3(dot(wi, X), dot(wi, Y), dot(wi, Z));
float3 local_O = make_float3(dot(wo, X), dot(wo, Y), dot(wo, Z));
if (is_aniso)
*pdf = mf_ggx_aniso_pdf(local_I, local_O, make_float2(bsdf->alpha_x, bsdf->alpha_y));
else
*pdf = mf_ggx_pdf(local_I, local_O, bsdf->alpha_x);
if (*pdf <= 0.f) {
*pdf = 0.f;
return make_float3(0.f, 0.f, 0.f);
}
return mf_eval_glossy(local_I,
local_O,
true,
bsdf->extra->color,
bsdf->alpha_x,
bsdf->alpha_y,
lcg_state,
bsdf->ior,
use_fresnel,
bsdf->extra->cspec0);
}
ccl_device int bsdf_microfacet_multi_ggx_sample(KernelGlobals kg,
ccl_private const ShaderClosure *sc,
float3 Ng,
float3 wi,
float randu,
float randv,
ccl_private Spectrum *eval,
ccl_private float3 *wo,
ccl_private float *pdf,
ccl_private uint *lcg_state,
ccl_private float2 *sampled_roughness,
ccl_private float *eta)
{
ccl_private const MicrofacetBsdf *bsdf = (ccl_private const MicrofacetBsdf *)sc;
float3 X, Y, Z;
Z = bsdf->N;
/* Ensure that the view direction is on the outside w.r.t. the shading normal. */
if (dot(Z, wi) <= 0.0f) {
*pdf = 0.0f;
return LABEL_NONE;
}
/* Special case: Extremely low roughness.
* Don't bother with microfacets, just do specular reflection. */
if (bsdf->alpha_x * bsdf->alpha_y < 1e-7f) {
*wo = 2 * dot(Z, wi) * Z - wi;
if (dot(Ng, *wo) <= 0.0f) {
*pdf = 0.0f;
return LABEL_NONE;
}
*pdf = 1e6f;
*eval = make_spectrum(1e6f);
return LABEL_REFLECT | LABEL_SINGULAR;
}
bool use_fresnel = (bsdf->type == CLOSURE_BSDF_MICROFACET_MULTI_GGX_FRESNEL_ID);
*eta = bsdf->ior;
*sampled_roughness = make_float2(bsdf->alpha_x, bsdf->alpha_y);
bool is_aniso = (bsdf->alpha_x != bsdf->alpha_y);
if (is_aniso)
make_orthonormals_tangent(Z, bsdf->T, &X, &Y);
else
make_orthonormals(Z, &X, &Y);
float3 local_I = make_float3(dot(wi, X), dot(wi, Y), dot(wi, Z));
float3 local_O;
*eval = mf_sample_glossy(local_I,
&local_O,
bsdf->extra->color,
bsdf->alpha_x,
bsdf->alpha_y,
lcg_state,
bsdf->ior,
use_fresnel,
bsdf->extra->cspec0);
*wo = X * local_O.x + Y * local_O.y + Z * local_O.z;
/* Ensure that the light direction is on the outside w.r.t. the geometry normal. */
if (dot(Ng, *wo) <= 0.0f) {
*pdf = 0.0f;
return LABEL_NONE;
}
if (is_aniso)
*pdf = mf_ggx_aniso_pdf(local_I, local_O, make_float2(bsdf->alpha_x, bsdf->alpha_y));
else
*pdf = mf_ggx_pdf(local_I, local_O, bsdf->alpha_x);
*pdf = fmaxf(0.f, *pdf);
*eval *= *pdf;
return LABEL_REFLECT | LABEL_GLOSSY;
}
/* Multi-scattering GGX Glass closure */
ccl_device int bsdf_microfacet_multi_ggx_glass_setup(ccl_private MicrofacetBsdf *bsdf)
{
bsdf->alpha_x = clamp(bsdf->alpha_x, 1e-4f, 1.0f);
bsdf->alpha_y = bsdf->alpha_x;
bsdf->ior = max(0.0f, bsdf->ior);
bsdf->extra->color = saturate(bsdf->extra->color);
bsdf->type = CLOSURE_BSDF_MICROFACET_MULTI_GGX_GLASS_ID;
return SD_BSDF | SD_BSDF_HAS_EVAL | SD_BSDF_NEEDS_LCG | SD_BSDF_HAS_TRANSMISSION;
}
ccl_device int bsdf_microfacet_multi_ggx_glass_fresnel_setup(ccl_private MicrofacetBsdf *bsdf,
ccl_private const ShaderData *sd)
{
bsdf->alpha_x = clamp(bsdf->alpha_x, 1e-4f, 1.0f);
bsdf->alpha_y = bsdf->alpha_x;
bsdf->ior = max(0.0f, bsdf->ior);
bsdf->extra->color = saturate(bsdf->extra->color);
bsdf->extra->cspec0 = saturate(bsdf->extra->cspec0);
bsdf->type = CLOSURE_BSDF_MICROFACET_MULTI_GGX_GLASS_FRESNEL_ID;
bsdf_microfacet_adjust_weight(sd, bsdf);
return SD_BSDF | SD_BSDF_HAS_EVAL | SD_BSDF_NEEDS_LCG;
}
ccl_device Spectrum bsdf_microfacet_multi_ggx_glass_eval(ccl_private const ShaderClosure *sc,
const float3 wi,
const float3 wo,
ccl_private float *pdf,
ccl_private uint *lcg_state)
{
ccl_private const MicrofacetBsdf *bsdf = (ccl_private const MicrofacetBsdf *)sc;
if (bsdf->alpha_x * bsdf->alpha_y < 1e-7f) {
*pdf = 0.0f;
return zero_spectrum();
}
float3 X, Y, Z;
Z = bsdf->N;
make_orthonormals(Z, &X, &Y);
float3 local_I = make_float3(dot(wi, X), dot(wi, Y), dot(wi, Z));
float3 local_O = make_float3(dot(wo, X), dot(wo, Y), dot(wo, Z));
const bool is_transmission = local_O.z < 0.0f;
const bool use_fresnel = !is_transmission &&
(bsdf->type == CLOSURE_BSDF_MICROFACET_MULTI_GGX_GLASS_FRESNEL_ID);
*pdf = mf_glass_pdf(local_I, local_O, bsdf->alpha_x, bsdf->ior);
kernel_assert(*pdf >= 0.f);
return mf_eval_glass(local_I,
local_O,
!is_transmission,
bsdf->extra->color,
bsdf->alpha_x,
bsdf->alpha_y,
lcg_state,
bsdf->ior,
use_fresnel,
(is_transmission) ? bsdf->extra->color : bsdf->extra->cspec0);
}
ccl_device int bsdf_microfacet_multi_ggx_glass_sample(KernelGlobals kg,
ccl_private const ShaderClosure *sc,
float3 Ng,
float3 wi,
float randu,
float randv,
ccl_private Spectrum *eval,
ccl_private float3 *wo,
ccl_private float *pdf,
ccl_private uint *lcg_state,
ccl_private float2 *sampled_roughness,
ccl_private float *eta)
{
ccl_private const MicrofacetBsdf *bsdf = (ccl_private const MicrofacetBsdf *)sc;
float3 X, Y, Z;
Z = bsdf->N;
*eta = bsdf->ior;
*sampled_roughness = make_float2(bsdf->alpha_x, bsdf->alpha_y);
if (bsdf->alpha_x * bsdf->alpha_y < 1e-7f) {
float3 R, T;
bool inside;
float fresnel = fresnel_dielectric(bsdf->ior, Z, wi, &R, &T, &inside);
*pdf = 1e6f;
*eval = make_spectrum(1e6f);
if (randu < fresnel) {
*wo = R;
return LABEL_REFLECT | LABEL_SINGULAR;
}
else {
*wo = T;
return LABEL_TRANSMIT | LABEL_SINGULAR;
}
}
bool use_fresnel = (bsdf->type == CLOSURE_BSDF_MICROFACET_MULTI_GGX_GLASS_FRESNEL_ID);
make_orthonormals(Z, &X, &Y);
float3 local_I = make_float3(dot(wi, X), dot(wi, Y), dot(wi, Z));
float3 local_O;
*eval = mf_sample_glass(local_I,
&local_O,
bsdf->extra->color,
bsdf->alpha_x,
bsdf->alpha_y,
lcg_state,
bsdf->ior,
use_fresnel,
bsdf->extra->cspec0);
*pdf = mf_glass_pdf(local_I, local_O, bsdf->alpha_x, bsdf->ior);
kernel_assert(*pdf >= 0.f);
*eval *= *pdf;
*wo = X * local_O.x + Y * local_O.y + Z * local_O.z;
if (local_O.z * local_I.z > 0.0f) {
return LABEL_REFLECT | LABEL_GLOSSY;
}
else {
return LABEL_TRANSMIT | LABEL_GLOSSY;
}
}
CCL_NAMESPACE_END
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