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intern/cycles/kernel/closure/bsdf_microfacet.h

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} }
/* Beckmann and GGX microfacet importance sampling from: /* Beckmann and GGX microfacet importance sampling from:
* *
* Importance Sampling Microfacet-Based BSDFs using the Distribution of Visible Normals. * Importance Sampling Microfacet-Based BSDFs using the Distribution of Visible Normals.
* E. Heitz and E. d'Eon, EGSR 2014 */ * E. Heitz and E. d'Eon, EGSR 2014 */
ccl_device_inline void microfacet_beckmann_sample_slopes( ccl_device_inline void microfacet_beckmann_sample_slopes(
KernelGlobals *kg,
const float cos_theta_i, const float sin_theta_i, const float cos_theta_i, const float sin_theta_i,
const float alpha_x, const float alpha_y,
float randu, float randv, float *slope_x, float *slope_y, float randu, float randv, float *slope_x, float *slope_y,
float *G1i) float *G1i)
{ {
/* special case (normal incidence) */ /* special case (normal incidence) */
if(cos_theta_i >= 0.99999f) { if(cos_theta_i >= 0.99999f) {
const float r = sqrtf(-logf(randu)); const float r = sqrtf(-logf(randu));
const float phi = M_2PI_F * randv; const float phi = M_2PI_F * randv;
*slope_x = r * cosf(phi); *slope_x = r * cosf(phi);
*slope_y = r * sinf(phi); *slope_y = r * sinf(phi);
*G1i = 1.0f; *G1i = 1.0f;
return; return;
} }
/* precomputations */ /* precomputations */
const float tan_theta_i = sin_theta_i/cos_theta_i; const float tan_theta_i = sin_theta_i/cos_theta_i;
const float inv_a = tan_theta_i; const float inv_a = tan_theta_i;
const float a = 1.0f/inv_a; const float a = 1.0f/inv_a;
const float erf_a = approx_erff(a); const float erf_a = approx_erff(a);
const float exp_a2 = expf(-a*a); const float exp_a2 = expf(-a*a);
const float SQRT_PI_INV = 0.56418958354f; const float SQRT_PI_INV = 0.56418958354f;
const float Lambda = 0.5f*(erf_a - 1.0f) + (0.5f*SQRT_PI_INV)*(exp_a2*inv_a); const float Lambda = 0.5f*(erf_a - 1.0f) + (0.5f*SQRT_PI_INV)*(exp_a2*inv_a);
const float G1 = 1.0f/(1.0f + Lambda); /* masking */ const float G1 = 1.0f/(1.0f + Lambda); /* masking */
const float C = 1.0f - G1 * erf_a;
*G1i = G1; *G1i = G1;
#if 0
const float C = 1.0f - G1 * erf_a;
/* sample slope X */ /* sample slope X */
if(randu < C) { if(randu < C) {
/* rescale randu */ /* rescale randu */
randu = randu / C; randu = randu / C;
const float w_1 = 0.5f * SQRT_PI_INV * sin_theta_i * exp_a2; const float w_1 = 0.5f * SQRT_PI_INV * sin_theta_i * exp_a2;
const float w_2 = cos_theta_i * (0.5f - 0.5f*erf_a); const float w_2 = cos_theta_i * (0.5f - 0.5f*erf_a);
const float p = w_1 / (w_1 + w_2); const float p = w_1 / (w_1 + w_2);
Show All 18 Lines if(randv > p) {
randv = (randv - p) / (1.0f - p); randv = (randv - p) / (1.0f - p);
} }
else else
randv = randv / p; randv = randv / p;
} }
/* sample slope Y */ /* sample slope Y */
*slope_y = approx_erfinvf(2.0f*randv - 1.0f); *slope_y = approx_erfinvf(2.0f*randv - 1.0f);
#else
/* use precomputed table, because it better preserves stratification
* of the random number pattern */
int beckmann_table_offset = kernel_data.tables.beckmann_offset;
*slope_x = lookup_table_read_2D(kg, randu, cos_theta_i,
beckmann_table_offset, BECKMANN_TABLE_SIZE, BECKMANN_TABLE_SIZE);
*slope_y = approx_erfinvf(2.0f*randv - 1.0f);
#endif
} }
ccl_device_inline void microfacet_ggx_sample_slopes( ccl_device_inline void microfacet_ggx_sample_slopes(
const float cos_theta_i, const float sin_theta_i, const float cos_theta_i, const float sin_theta_i,
const float alpha_x, const float alpha_y,
float randu, float randv, float *slope_x, float *slope_y, float randu, float randv, float *slope_x, float *slope_y,
float *G1i) float *G1i)
{ {
/* special case (normal incidence) */ /* special case (normal incidence) */
if(cos_theta_i >= 0.99999f) { if(cos_theta_i >= 0.99999f) {
const float r = sqrtf(randu/(1.0f - randu)); const float r = sqrtf(randu/(1.0f - randu));
const float phi = M_2PI_F * randv; const float phi = M_2PI_F * randv;
*slope_x = r * cosf(phi); *slope_x = r * cosf(phi);
Show All 31 Lines else {
S = -1.0f; S = -1.0f;
randv = 2.0f*(0.5f - randv); randv = 2.0f*(0.5f - randv);
} }
const float z = (randv*(randv*(randv*0.27385f - 0.73369f) + 0.46341f)) / (randv*(randv*(randv*0.093073f + 0.309420f) - 1.000000f) + 0.597999f); const float z = (randv*(randv*(randv*0.27385f - 0.73369f) + 0.46341f)) / (randv*(randv*(randv*0.093073f + 0.309420f) - 1.000000f) + 0.597999f);
*slope_y = S * z * safe_sqrtf(1.0f + (*slope_x)*(*slope_x)); *slope_y = S * z * safe_sqrtf(1.0f + (*slope_x)*(*slope_x));
} }
ccl_device_inline float3 microfacet_sample_stretched(const float3 omega_i, ccl_device_inline float3 microfacet_sample_stretched(
KernelGlobals *kg, const float3 omega_i,
const float alpha_x, const float alpha_y, const float alpha_x, const float alpha_y,
const float randu, const float randv, const float randu, const float randv,
bool beckmann, float *G1i) bool beckmann, float *G1i)
{ {
/* 1. stretch omega_i */ /* 1. stretch omega_i */
float3 omega_i_ = make_float3(alpha_x * omega_i.x, alpha_y * omega_i.y, omega_i.z); float3 omega_i_ = make_float3(alpha_x * omega_i.x, alpha_y * omega_i.y, omega_i.z);
omega_i_ = normalize(omega_i_); omega_i_ = normalize(omega_i_);
Show All 10 Lines if(omega_i_.z < 0.99999f) {
float invlen = 1.0f/sintheta_; float invlen = 1.0f/sintheta_;
cosphi_ = omega_i_.x * invlen; cosphi_ = omega_i_.x * invlen;
sinphi_ = omega_i_.y * invlen; sinphi_ = omega_i_.y * invlen;
} }
/* 2. sample P22_{omega_i}(x_slope, y_slope, 1, 1) */ /* 2. sample P22_{omega_i}(x_slope, y_slope, 1, 1) */
float slope_x, slope_y; float slope_x, slope_y;
if(beckmann) if(beckmann) {
microfacet_beckmann_sample_slopes(costheta_, sintheta_, microfacet_beckmann_sample_slopes(kg, costheta_, sintheta_,
alpha_x, alpha_y, randu, randv, &slope_x, &slope_y, G1i); randu, randv, &slope_x, &slope_y, G1i);
else }
else {
microfacet_ggx_sample_slopes(costheta_, sintheta_, microfacet_ggx_sample_slopes(costheta_, sintheta_,
alpha_x, alpha_y, randu, randv, &slope_x, &slope_y, G1i); randu, randv, &slope_x, &slope_y, G1i);
}
/* 3. rotate */ /* 3. rotate */
float tmp = cosphi_*slope_x - sinphi_*slope_y; float tmp = cosphi_*slope_x - sinphi_*slope_y;
slope_y = sinphi_*slope_x + cosphi_*slope_y; slope_y = sinphi_*slope_x + cosphi_*slope_y;
slope_x = tmp; slope_x = tmp;
/* 4. unstretch */ /* 4. unstretch */
slope_x = alpha_x * slope_x; slope_x = alpha_x * slope_x;
▲ Show 20 Lines • Show All 191 Lines • ▼ Show 20 Linesccl_device float3 bsdf_microfacet_ggx_eval_transmit(const ShaderClosure *sc, const float3 I, const float3 omega_in, float *pdf)
* pdf = pm * (m_eta * m_eta) * fabsf(cosHI) / Ht2 */ * pdf = pm * (m_eta * m_eta) * fabsf(cosHI) / Ht2 */
float common = D * (m_eta * m_eta) / (cosNO * Ht2); float common = D * (m_eta * m_eta) / (cosNO * Ht2);
float out = G * fabsf(cosHI * cosHO) * common; float out = G * fabsf(cosHI * cosHO) * common;
*pdf = G1o * cosHO * fabsf(cosHI) * common; *pdf = G1o * cosHO * fabsf(cosHI) * common;
return make_float3(out, out, out); return make_float3(out, out, out);
} }
ccl_device int bsdf_microfacet_ggx_sample(const ShaderClosure *sc, float3 Ng, float3 I, float3 dIdx, float3 dIdy, float randu, float randv, float3 *eval, float3 *omega_in, float3 *domega_in_dx, float3 *domega_in_dy, float *pdf) ccl_device int bsdf_microfacet_ggx_sample(KernelGlobals *kg, const ShaderClosure *sc, float3 Ng, float3 I, float3 dIdx, float3 dIdy, float randu, float randv, float3 *eval, float3 *omega_in, float3 *domega_in_dx, float3 *domega_in_dy, float *pdf)
{ {
float alpha_x = sc->data0; float alpha_x = sc->data0;
float alpha_y = sc->data1; float alpha_y = sc->data1;
int m_refractive = sc->type == CLOSURE_BSDF_MICROFACET_GGX_REFRACTION_ID; int m_refractive = sc->type == CLOSURE_BSDF_MICROFACET_GGX_REFRACTION_ID;
float3 N = sc->N; float3 N = sc->N;
float cosNO = dot(N, I); float cosNO = dot(N, I);
if(cosNO > 0) { if(cosNO > 0) {
float3 X, Y, Z = N; float3 X, Y, Z = N;
if(alpha_x == alpha_y) if(alpha_x == alpha_y)
make_orthonormals(Z, &X, &Y); make_orthonormals(Z, &X, &Y);
else else
make_orthonormals_tangent(Z, sc->T, &X, &Y); make_orthonormals_tangent(Z, sc->T, &X, &Y);
/* importance sampling with distribution of visible normals. vectors are /* importance sampling with distribution of visible normals. vectors are
* transformed to local space before and after */ * transformed to local space before and after */
float3 local_I = make_float3(dot(X, I), dot(Y, I), cosNO); float3 local_I = make_float3(dot(X, I), dot(Y, I), cosNO);
float3 local_m; float3 local_m;
float G1o; float G1o;
local_m = microfacet_sample_stretched(local_I, alpha_x, alpha_y, local_m = microfacet_sample_stretched(kg, local_I, alpha_x, alpha_y,
randu, randv, false, &G1o); randu, randv, false, &G1o);
float3 m = X*local_m.x + Y*local_m.y + Z*local_m.z; float3 m = X*local_m.x + Y*local_m.y + Z*local_m.z;
float cosThetaM = local_m.z; float cosThetaM = local_m.z;
/* reflection or refraction? */ /* reflection or refraction? */
if(!m_refractive) { if(!m_refractive) {
float cosMO = dot(m, I); float cosMO = dot(m, I);
▲ Show 20 Lines • Show All 309 Lines • ▼ Show 20 Linesccl_device float3 bsdf_microfacet_beckmann_eval_transmit(const ShaderClosure *sc, const float3 I, const float3 omega_in, float *pdf)
* pdf = pm * (m_eta * m_eta) * fabsf(cosHI) / Ht2 */ * pdf = pm * (m_eta * m_eta) * fabsf(cosHI) / Ht2 */
float common = D * (m_eta * m_eta) / (cosNO * Ht2); float common = D * (m_eta * m_eta) / (cosNO * Ht2);
float out = G * fabsf(cosHI * cosHO) * common; float out = G * fabsf(cosHI * cosHO) * common;
*pdf = G1o * cosHO * fabsf(cosHI) * common; *pdf = G1o * cosHO * fabsf(cosHI) * common;
return make_float3(out, out, out); return make_float3(out, out, out);
} }
ccl_device int bsdf_microfacet_beckmann_sample(const ShaderClosure *sc, float3 Ng, float3 I, float3 dIdx, float3 dIdy, float randu, float randv, float3 *eval, float3 *omega_in, float3 *domega_in_dx, float3 *domega_in_dy, float *pdf) ccl_device int bsdf_microfacet_beckmann_sample(KernelGlobals *kg, const ShaderClosure *sc, float3 Ng, float3 I, float3 dIdx, float3 dIdy, float randu, float randv, float3 *eval, float3 *omega_in, float3 *domega_in_dx, float3 *domega_in_dy, float *pdf)
{ {
float alpha_x = sc->data0; float alpha_x = sc->data0;
float alpha_y = sc->data1; float alpha_y = sc->data1;
int m_refractive = sc->type == CLOSURE_BSDF_MICROFACET_BECKMANN_REFRACTION_ID; int m_refractive = sc->type == CLOSURE_BSDF_MICROFACET_BECKMANN_REFRACTION_ID;
float3 N = sc->N; float3 N = sc->N;
float cosNO = dot(N, I); float cosNO = dot(N, I);
if(cosNO > 0) { if(cosNO > 0) {
float3 X, Y, Z = N; float3 X, Y, Z = N;
if(alpha_x == alpha_y) if(alpha_x == alpha_y)
make_orthonormals(Z, &X, &Y); make_orthonormals(Z, &X, &Y);
else else
make_orthonormals_tangent(Z, sc->T, &X, &Y); make_orthonormals_tangent(Z, sc->T, &X, &Y);
/* importance sampling with distribution of visible normals. vectors are /* importance sampling with distribution of visible normals. vectors are
* transformed to local space before and after */ * transformed to local space before and after */
float3 local_I = make_float3(dot(X, I), dot(Y, I), cosNO); float3 local_I = make_float3(dot(X, I), dot(Y, I), cosNO);
float3 local_m; float3 local_m;
float G1o; float G1o;
local_m = microfacet_sample_stretched(local_I, alpha_x, alpha_x, local_m = microfacet_sample_stretched(kg, local_I, alpha_x, alpha_x,
randu, randv, true, &G1o); randu, randv, true, &G1o);
float3 m = X*local_m.x + Y*local_m.y + Z*local_m.z; float3 m = X*local_m.x + Y*local_m.y + Z*local_m.z;
float cosThetaM = local_m.z; float cosThetaM = local_m.z;
/* reflection or refraction? */ /* reflection or refraction? */
if(!m_refractive) { if(!m_refractive) {
float cosMO = dot(m, I); float cosMO = dot(m, I);
▲ Show 20 Lines • Show All 141 Lines • Show Last 20 Lines