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Diffstat (limited to 'intern/cycles/kernel/closure/bsdf_hair_principled.h')
| -rw-r--r-- | intern/cycles/kernel/closure/bsdf_hair_principled.h | 502 |
1 files changed, 502 insertions, 0 deletions
diff --git a/intern/cycles/kernel/closure/bsdf_hair_principled.h b/intern/cycles/kernel/closure/bsdf_hair_principled.h new file mode 100644 index 00000000000..4ee58089384 --- /dev/null +++ b/intern/cycles/kernel/closure/bsdf_hair_principled.h @@ -0,0 +1,502 @@ +/* + * Copyright 2018 Blender Foundation + * + * Licensed under the Apache License, Version 2.0 (the "License"); + * you may not use this file except in compliance with the License. + * You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ + +#ifdef __KERNEL_CPU__ +#include <fenv.h> +#endif + +#include "kernel/kernel_color.h" + +#ifndef __BSDF_HAIR_PRINCIPLED_H__ +#define __BSDF_HAIR_PRINCIPLED_H__ + +CCL_NAMESPACE_BEGIN + +typedef ccl_addr_space struct PrincipledHairExtra { + /* Geometry data. */ + float4 geom; +} PrincipledHairExtra; + +typedef ccl_addr_space struct PrincipledHairBSDF { + SHADER_CLOSURE_BASE; + + /* Absorption coefficient. */ + float3 sigma; + /* Variance of the underlying logistic distribution. */ + float v; + /* Scale factor of the underlying logistic distribution. */ + float s; + /* Cuticle tilt angle. */ + float alpha; + /* IOR. */ + float eta; + /* Effective variance for the diffuse bounce only. */ + float m0_roughness; + + /* Extra closure. */ + PrincipledHairExtra *extra; +} PrincipledHairBSDF; + +static_assert(sizeof(ShaderClosure) >= sizeof(PrincipledHairBSDF), "PrincipledHairBSDF is too large!"); +static_assert(sizeof(ShaderClosure) >= sizeof(PrincipledHairExtra), "PrincipledHairExtra is too large!"); + +ccl_device_inline float cos_from_sin(const float s) +{ + return safe_sqrtf(1.0f - s*s); +} + +/* Gives the change in direction in the normal plane for the given angles and p-th-order scattering. */ +ccl_device_inline float delta_phi(int p, float gamma_o, float gamma_t) +{ + return 2.0f * p * gamma_t - 2.0f * gamma_o + p * M_PI_F; +} + +/* Remaps the given angle to [-pi, pi]. */ +ccl_device_inline float wrap_angle(float a) +{ + while(a > M_PI_F) { + a -= M_2PI_F; + } + while(a < -M_PI_F) { + a += M_2PI_F; + } + return a; +} + +/* Logistic distribution function. */ +ccl_device_inline float logistic(float x, float s) +{ + float v = expf(-fabsf(x)/s); + return v / (s * sqr(1.0f + v)); +} + +/* Logistic cumulative density function. */ +ccl_device_inline float logistic_cdf(float x, float s) +{ + float arg = -x/s; + /* expf() overflows if arg >= 89.0. */ + if(arg > 88.0f) { + return 0.0f; + } + else { + return 1.0f / (1.0f + expf(arg)); + } +} + +/* Numerical approximation to the Bessel function of the first kind. */ +ccl_device_inline float bessel_I0(float x) +{ + x = sqr(x); + float val = 1.0f + 0.25f*x; + float pow_x_2i = sqr(x); + uint64_t i_fac_2 = 1; + int pow_4_i = 16; + for(int i = 2; i < 10; i++) { + i_fac_2 *= i*i; + float newval = val + pow_x_2i / (pow_4_i * i_fac_2); + if(val == newval) { + return val; + } + val = newval; + pow_x_2i *= x; + pow_4_i *= 4; + } + return val; +} + +/* Logarithm of the Bessel function of the first kind. */ +ccl_device_inline float log_bessel_I0(float x) +{ + if (x > 12.0f) { + /* log(1/x) == -log(x) iff x > 0. + * This is only used with positive cosines */ + return x + 0.5f * (1.f / (8.0f * x) - M_LN_2PI_F - logf(x)); + } + else { + return logf(bessel_I0(x)); + } +} + +/* Logistic distribution limited to the interval [-pi, pi]. */ +ccl_device_inline float trimmed_logistic(float x, float s) +{ + /* The logistic distribution is symmetric and centered around zero, + * so logistic_cdf(x, s) = 1 - logistic_cdf(-x, s). + * Therefore, logistic_cdf(x, s)-logistic_cdf(-x, s) = 1 - 2*logistic_cdf(-x, s) */ + float scaling_fac = 1.0f - 2.0f*logistic_cdf(-M_PI_F, s); + float val = logistic(x, s); + return safe_divide(val, scaling_fac); +} + +/* Sampling function for the trimmed logistic function. */ +ccl_device_inline float sample_trimmed_logistic(float u, float s) +{ + float cdf_minuspi = logistic_cdf(-M_PI_F, s); + float x = -s*logf(1.0f / (u*(1.0f - 2.0f*cdf_minuspi) + cdf_minuspi) - 1.0f); + return clamp(x, -M_PI_F, M_PI_F); +} + +/* Azimuthal scattering function Np. */ +ccl_device_inline float azimuthal_scattering(float phi, + int p, + float s, + float gamma_o, + float gamma_t) +{ + float phi_o = wrap_angle(phi - delta_phi(p, gamma_o, gamma_t)); + float val = trimmed_logistic(phi_o, s); + return val; +} + +/* Longitudinal scattering function Mp. */ +ccl_device_inline float longitudinal_scattering(float sin_theta_i, + float cos_theta_i, + float sin_theta_o, + float cos_theta_o, + float v) +{ + float inv_v = 1.0f/v; + float cos_arg = cos_theta_i * cos_theta_o * inv_v; + float sin_arg = sin_theta_i * sin_theta_o * inv_v; + if(v <= 0.1f) { + float i0 = log_bessel_I0(cos_arg); + float val = expf(i0 - sin_arg - inv_v + 0.6931f + logf(0.5f*inv_v)); + return val; + } + else { + float i0 = bessel_I0(cos_arg); + float val = (expf(-sin_arg) * i0) / (sinhf(inv_v) * 2.0f * v); + return val; + } +} + +/* Combine the three values using their luminances. */ +ccl_device_inline float4 combine_with_energy(KernelGlobals *kg, float3 c) +{ + return make_float4(c.x, c.y, c.z, linear_rgb_to_gray(kg, c)); +} + +#ifdef __HAIR__ +/* Set up the hair closure. */ +ccl_device int bsdf_principled_hair_setup(ShaderData *sd, PrincipledHairBSDF *bsdf) +{ + bsdf->type = CLOSURE_BSDF_HAIR_PRINCIPLED_ID; + bsdf->v = clamp(bsdf->v, 0.001f, 1.0f); + bsdf->s = clamp(bsdf->s, 0.001f, 1.0f); + /* Apply Primary Reflection Roughness modifier. */ + bsdf->m0_roughness = clamp(bsdf->m0_roughness*bsdf->v, 0.001f, 1.0f); + + /* Map from roughness_u and roughness_v to variance and scale factor. */ + bsdf->v = sqr(0.726f*bsdf->v + 0.812f*sqr(bsdf->v) + 3.700f*pow20(bsdf->v)); + bsdf->s = (0.265f*bsdf->s + 1.194f*sqr(bsdf->s) + 5.372f*pow22(bsdf->s))*M_SQRT_PI_8_F; + bsdf->m0_roughness = sqr(0.726f*bsdf->m0_roughness + 0.812f*sqr(bsdf->m0_roughness) + 3.700f*pow20(bsdf->m0_roughness)); + + /* Compute local frame, aligned to curve tangent and ray direction. */ + float3 X = safe_normalize(sd->dPdu); + float3 Y = safe_normalize(cross(X, sd->I)); + float3 Z = safe_normalize(cross(X, Y)); + /* TODO: the solution below works where sd->Ng is the normal + * pointing from the center of the curve to the shading point. + * It doesn't work for triangles, see https://developer.blender.org/T43625 */ + + /* h -1..0..1 means the rays goes from grazing the hair, to hitting it at + * the center, to grazing the other edge. This is the sine of the angle + * between sd->Ng and Z, as seen from the tangent X. */ + + /* TODO: we convert this value to a cosine later and discard the sign, so + * we could probably save some operations. */ + float h = dot(cross(sd->Ng, X), Z); + + kernel_assert(fabsf(h) < 1.0f + 1e-4f); + kernel_assert(isfinite3_safe(Y)); + kernel_assert(isfinite_safe(h)); + + bsdf->extra->geom = make_float4(Y.x, Y.y, Y.z, h); + + return SD_BSDF|SD_BSDF_HAS_EVAL|SD_BSDF_NEEDS_LCG; +} + +#endif /* __HAIR__ */ + +/* Given the Fresnel term and transmittance, generate the attenuation terms for each bounce. */ +ccl_device_inline void hair_attenuation(KernelGlobals *kg, + float f, + float3 T, + float4 *Ap) +{ + /* Primary specular (R). */ + Ap[0] = make_float4(f, f, f, f); + + /* Transmission (TT). */ + float3 col = sqr(1.0f - f) * T; + Ap[1] = combine_with_energy(kg, col); + + /* Secondary specular (TRT). */ + col *= T*f; + Ap[2] = combine_with_energy(kg, col); + + /* Residual component (TRRT+). */ + col *= safe_divide_color(T*f, make_float3(1.0f, 1.0f, 1.0f) - T*f); + Ap[3] = combine_with_energy(kg, col); + + /* Normalize sampling weights. */ + float totweight = Ap[0].w + Ap[1].w + Ap[2].w + Ap[3].w; + float fac = safe_divide(1.0f, totweight); + + Ap[0].w *= fac; + Ap[1].w *= fac; + Ap[2].w *= fac; + Ap[3].w *= fac; +} + +/* Given the tilt angle, generate the rotated theta_i for the different bounces. */ +ccl_device_inline void hair_alpha_angles(float sin_theta_i, + float cos_theta_i, + float alpha, + float *angles) +{ + float sin_1alpha = sinf(alpha); + float cos_1alpha = cos_from_sin(sin_1alpha); + float sin_2alpha = 2.0f*sin_1alpha*cos_1alpha; + float cos_2alpha = sqr(cos_1alpha) - sqr(sin_1alpha); + float sin_4alpha = 2.0f*sin_2alpha*cos_2alpha; + float cos_4alpha = sqr(cos_2alpha) - sqr(sin_2alpha); + + angles[0] = sin_theta_i*cos_2alpha + cos_theta_i*sin_2alpha; + angles[1] = fabsf(cos_theta_i*cos_2alpha - sin_theta_i*sin_2alpha); + angles[2] = sin_theta_i*cos_1alpha - cos_theta_i*sin_1alpha; + angles[3] = fabsf(cos_theta_i*cos_1alpha + sin_theta_i*sin_1alpha); + angles[4] = sin_theta_i*cos_4alpha - cos_theta_i*sin_4alpha; + angles[5] = fabsf(cos_theta_i*cos_4alpha + sin_theta_i*sin_4alpha); +} + +/* Evaluation function for our shader. */ +ccl_device float3 bsdf_principled_hair_eval(KernelGlobals *kg, + const ShaderData *sd, + const ShaderClosure *sc, + const float3 omega_in, + float *pdf) +{ + kernel_assert(isfinite3_safe(sd->P) && isfinite_safe(sd->ray_length)); + + const PrincipledHairBSDF *bsdf = (const PrincipledHairBSDF*) sc; + float3 Y = float4_to_float3(bsdf->extra->geom); + + float3 X = safe_normalize(sd->dPdu); + kernel_assert(fabsf(dot(X, Y)) < 1e-4f); + float3 Z = safe_normalize(cross(X, Y)); + + float3 wo = make_float3(dot(sd->I, X), dot(sd->I, Y), dot(sd->I, Z)); + float3 wi = make_float3(dot(omega_in, X), dot(omega_in, Y), dot(omega_in, Z)); + + float sin_theta_o = wo.x; + float cos_theta_o = cos_from_sin(sin_theta_o); + float phi_o = atan2f(wo.z, wo.y); + + float sin_theta_t = sin_theta_o / bsdf->eta; + float cos_theta_t = cos_from_sin(sin_theta_t); + + float sin_gamma_o = bsdf->extra->geom.w; + float cos_gamma_o = cos_from_sin(sin_gamma_o); + float gamma_o = safe_asinf(sin_gamma_o); + + float sin_gamma_t = sin_gamma_o * cos_theta_o / sqrtf(sqr(bsdf->eta) - sqr(sin_theta_o)); + float cos_gamma_t = cos_from_sin(sin_gamma_t); + float gamma_t = safe_asinf(sin_gamma_t); + + float3 T = exp3(-bsdf->sigma * (2.0f * cos_gamma_t / cos_theta_t)); + float4 Ap[4]; + hair_attenuation(kg, fresnel_dielectric_cos(cos_theta_o * cos_gamma_o, bsdf->eta), T, Ap); + + float sin_theta_i = wi.x; + float cos_theta_i = cos_from_sin(sin_theta_i); + float phi_i = atan2f(wi.z, wi.y); + + float phi = phi_i - phi_o; + + float angles[6]; + hair_alpha_angles(sin_theta_i, cos_theta_i, bsdf->alpha, angles); + + float4 F; + float Mp, Np; + + /* Primary specular (R). */ + Mp = longitudinal_scattering(angles[0], angles[1], sin_theta_o, cos_theta_o, bsdf->m0_roughness); + Np = azimuthal_scattering(phi, 0, bsdf->s, gamma_o, gamma_t); + F = Ap[0] * Mp * Np; + kernel_assert(isfinite3_safe(float4_to_float3(F))); + + /* Transmission (TT). */ + Mp = longitudinal_scattering(angles[2], angles[3], sin_theta_o, cos_theta_o, 0.25f*bsdf->v); + Np = azimuthal_scattering(phi, 1, bsdf->s, gamma_o, gamma_t); + F += Ap[1] * Mp * Np; + kernel_assert(isfinite3_safe(float4_to_float3(F))); + + /* Secondary specular (TRT). */ + Mp = longitudinal_scattering(angles[4], angles[5], sin_theta_o, cos_theta_o, 4.0f*bsdf->v); + Np = azimuthal_scattering(phi, 2, bsdf->s, gamma_o, gamma_t); + F += Ap[2] * Mp * Np; + kernel_assert(isfinite3_safe(float4_to_float3(F))); + + /* Residual component (TRRT+). */ + Mp = longitudinal_scattering(sin_theta_i, cos_theta_i, sin_theta_o, cos_theta_o, 4.0f*bsdf->v); + Np = M_1_2PI_F; + F += Ap[3] * Mp * Np; + kernel_assert(isfinite3_safe(float4_to_float3(F))); + + *pdf = F.w; + return float4_to_float3(F); +} + +/* Sampling function for the hair shader. */ +ccl_device int bsdf_principled_hair_sample(KernelGlobals *kg, + const ShaderClosure *sc, + ShaderData *sd, + float randu, + float randv, + float3 *eval, + float3 *omega_in, + float3 *domega_in_dx, + float3 *domega_in_dy, + float *pdf) +{ + PrincipledHairBSDF *bsdf = (PrincipledHairBSDF*) sc; + + float3 Y = float4_to_float3(bsdf->extra->geom); + + float3 X = safe_normalize(sd->dPdu); + kernel_assert(fabsf(dot(X, Y)) < 1e-4f); + float3 Z = safe_normalize(cross(X, Y)); + + float3 wo = make_float3(dot(sd->I, X), dot(sd->I, Y), dot(sd->I, Z)); + + float2 u[2]; + u[0] = make_float2(randu, randv); + u[1].x = lcg_step_float_addrspace(&sd->lcg_state); + u[1].y = lcg_step_float_addrspace(&sd->lcg_state); + + float sin_theta_o = wo.x; + float cos_theta_o = cos_from_sin(sin_theta_o); + float phi_o = atan2f(wo.z, wo.y); + + float sin_theta_t = sin_theta_o / bsdf->eta; + float cos_theta_t = cos_from_sin(sin_theta_t); + + float sin_gamma_o = bsdf->extra->geom.w; + float cos_gamma_o = cos_from_sin(sin_gamma_o); + float gamma_o = safe_asinf(sin_gamma_o); + + float sin_gamma_t = sin_gamma_o * cos_theta_o / sqrtf(sqr(bsdf->eta) - sqr(sin_theta_o)); + float cos_gamma_t = cos_from_sin(sin_gamma_t); + float gamma_t = safe_asinf(sin_gamma_t); + + float3 T = exp3(-bsdf->sigma * (2.0f * cos_gamma_t / cos_theta_t)); + float4 Ap[4]; + hair_attenuation(kg, fresnel_dielectric_cos(cos_theta_o * cos_gamma_o, bsdf->eta), T, Ap); + + int p = 0; + for(; p < 3; p++) { + if(u[0].x < Ap[p].w) { + break; + } + u[0].x -= Ap[p].w; + } + + float v = bsdf->v; + if(p == 1) { + v *= 0.25f; + } + if(p >= 2) { + v *= 4.0f; + } + + u[1].x = max(u[1].x, 1e-5f); + float fac = 1.0f + v*logf(u[1].x + (1.0f - u[1].x)*expf(-2.0f/v)); + float sin_theta_i = -fac * sin_theta_o + cos_from_sin(fac) * cosf(M_2PI_F * u[1].y) * cos_theta_o; + float cos_theta_i = cos_from_sin(sin_theta_i); + + float angles[6]; + if(p < 3) { + hair_alpha_angles(sin_theta_i, cos_theta_i, -bsdf->alpha, angles); + sin_theta_i = angles[2*p]; + cos_theta_i = angles[2*p+1]; + } + + float phi; + if(p < 3) { + phi = delta_phi(p, gamma_o, gamma_t) + sample_trimmed_logistic(u[0].y, bsdf->s); + } + else { + phi = M_2PI_F*u[0].y; + } + float phi_i = phi_o + phi; + + hair_alpha_angles(sin_theta_i, cos_theta_i, bsdf->alpha, angles); + + float4 F; + float Mp, Np; + + /* Primary specular (R). */ + Mp = longitudinal_scattering(angles[0], angles[1], sin_theta_o, cos_theta_o, bsdf->m0_roughness); + Np = azimuthal_scattering(phi, 0, bsdf->s, gamma_o, gamma_t); + F = Ap[0] * Mp * Np; + kernel_assert(isfinite3_safe(float4_to_float3(F))); + + /* Transmission (TT). */ + Mp = longitudinal_scattering(angles[2], angles[3], sin_theta_o, cos_theta_o, 0.25f*bsdf->v); + Np = azimuthal_scattering(phi, 1, bsdf->s, gamma_o, gamma_t); + F += Ap[1] * Mp * Np; + kernel_assert(isfinite3_safe(float4_to_float3(F))); + + /* Secondary specular (TRT). */ + Mp = longitudinal_scattering(angles[4], angles[5], sin_theta_o, cos_theta_o, 4.0f*bsdf->v); + Np = azimuthal_scattering(phi, 2, bsdf->s, gamma_o, gamma_t); + F += Ap[2] * Mp * Np; + kernel_assert(isfinite3_safe(float4_to_float3(F))); + + /* Residual component (TRRT+). */ + Mp = longitudinal_scattering(sin_theta_i, cos_theta_i, sin_theta_o, cos_theta_o, 4.0f*bsdf->v); + Np = M_1_2PI_F; + F += Ap[3] * Mp * Np; + kernel_assert(isfinite3_safe(float4_to_float3(F))); + + *eval = float4_to_float3(F); + *pdf = F.w; + + *omega_in = X*sin_theta_i + Y*cos_theta_i*cosf(phi_i) + Z*cos_theta_i*sinf(phi_i); + +#ifdef __RAY_DIFFERENTIALS__ + float3 N = safe_normalize(sd->I + *omega_in); + *domega_in_dx = (2 * dot(N, sd->dI.dx)) * N - sd->dI.dx; + *domega_in_dy = (2 * dot(N, sd->dI.dy)) * N - sd->dI.dy; +#endif + + return LABEL_GLOSSY|((p == 0)? LABEL_REFLECT : LABEL_TRANSMIT); +} + +/* Implements Filter Glossy by capping the effective roughness. */ +ccl_device void bsdf_principled_hair_blur(ShaderClosure *sc, float roughness) +{ + PrincipledHairBSDF *bsdf = (PrincipledHairBSDF*)sc; + + bsdf->v = fmaxf(roughness, bsdf->v); + bsdf->s = fmaxf(roughness, bsdf->s); + bsdf->m0_roughness = fmaxf(roughness, bsdf->m0_roughness); +} + +CCL_NAMESPACE_END + +#endif /* __BSDF_HAIR_PRINCIPLED_H__ */ |