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Diffstat (limited to 'intern/cycles/kernel/closure/bsdf_ashikhmin_shirley.h')
-rw-r--r-- | intern/cycles/kernel/closure/bsdf_ashikhmin_shirley.h | 196 |
1 files changed, 196 insertions, 0 deletions
diff --git a/intern/cycles/kernel/closure/bsdf_ashikhmin_shirley.h b/intern/cycles/kernel/closure/bsdf_ashikhmin_shirley.h new file mode 100644 index 00000000000..ea5b610ae56 --- /dev/null +++ b/intern/cycles/kernel/closure/bsdf_ashikhmin_shirley.h @@ -0,0 +1,196 @@ +/* + * Copyright 2011-2013 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 + */ + +#ifndef __BSDF_ASHIKHMIN_SHIRLEY_H__ +#define __BSDF_ASHIKHMIN_SHIRLEY_H__ + +/* +ASHIKHMIN SHIRLEY BSDF + +Implementation of +Michael Ashikhmin and Peter Shirley: "An Anisotropic Phong BRDF Model" (2000) + +The Fresnel factor is missing to get a separable bsdf (intensity*color), as is +the case with all other microfacet-based BSDF implementations in Cycles. + +Other than that, the implementation directly follows the paper. +*/ + +CCL_NAMESPACE_BEGIN + + +ccl_device int bsdf_ashikhmin_shirley_setup(ShaderClosure *sc) +{ + sc->data0 = clamp(sc->data0, 1e-4f, 1.0f); /* store roughness. could already convert to exponent to save some cycles in eval, */ + sc->data1 = clamp(sc->data1, 1e-4f, 1.0f); /* but this is more consistent with other bsdfs and shader_blur. */ + + sc->type = CLOSURE_BSDF_ASHIKHMIN_SHIRLEY_ID; + return SD_BSDF | SD_BSDF_HAS_EVAL | SD_BSDF_GLOSSY; +} + +ccl_device void bsdf_ashikhmin_shirley_blur(ShaderClosure *sc, float roughness) +{ + sc->data0 = fmaxf(roughness, sc->data0); /* clamp roughness */ + sc->data1 = fmaxf(roughness, sc->data1); +} + +ccl_device_inline float bsdf_ashikhmin_shirley_roughness_to_exponent(float roughness) +{ + return 2.0f / (roughness*roughness) - 2.0f; +} + +ccl_device float3 bsdf_ashikhmin_shirley_eval_reflect(const ShaderClosure *sc, const float3 I, const float3 omega_in, float *pdf) +{ + float3 N = sc->N; + float3 T = sc->T; + + float NdotI = dot(N, I); /* in Cycles/OSL convention I is omega_out */ + float NdotO = dot(N, omega_in); /* and consequently we use for O omaga_in ;) */ + + float out = 0.0f; + + if (NdotI > 0.0f && NdotO > 0.0f) { + NdotI = fmaxf(NdotI, 1e-6f); + NdotO = fmaxf(NdotO, 1e-6f); + float3 H = normalize(omega_in + I); + float HdotI = fmaxf(dot(H, I), 1e-6f); + float HdotN = fmaxf(dot(H, N), 1e-6f); + + float pump = 1.0f / fmaxf(1e-6f, (HdotI*fmaxf(NdotO, NdotI))); /* pump from original paper (first derivative disc., but cancels the HdotI in the pdf nicely) */ + /*float pump = 1.0f / fmaxf(1e-4f, ((NdotO + NdotI) * (NdotO*NdotI))); */ /* pump from d-brdf paper */ + + float n_x = bsdf_ashikhmin_shirley_roughness_to_exponent(sc->data0); + float n_y = bsdf_ashikhmin_shirley_roughness_to_exponent(sc->data1); + + if (n_x == n_y) { /* => isotropic case */ + float e = n_x; + float lobe = powf(HdotN, e); + float norm = (n_x + 1.0f) / (8.0f * M_PI_F); + + out = NdotO * norm * lobe * pump; + *pdf = norm * lobe / HdotI; /* this is p_h / 4(H.I) (conversion from 'wh measure' to 'wi measure', eq. 8 in paper) */ + } + else { /* => ANisotropic case */ + float3 X, Y; + make_orthonormals_tangent(N, T, &X, &Y); + + float HdotX = dot(H, X); + float HdotY = dot(H, Y); + float e = (n_x * HdotX*HdotX + n_y * HdotY*HdotY) / (1.0f - HdotN*HdotN); + float lobe = powf(HdotN, e); + float norm = sqrtf((n_x + 1.0f)*(n_y + 1.0f)) / (8.0f * M_PI_F); + + out = NdotO * norm * lobe * pump; + *pdf = norm * lobe / HdotI; + } + } + + return make_float3(out, out, out); +} + +ccl_device float3 bsdf_ashikhmin_shirley_eval_transmit(const ShaderClosure *sc, const float3 I, const float3 omega_in, float *pdf) +{ + return make_float3(0.0f, 0.0f, 0.0f); +} + +ccl_device_inline void bsdf_ashikhmin_shirley_sample_first_quadrant(float n_x, float n_y, float randu, float randv, float *phi, float *cos_theta) +{ + *phi = atanf(sqrtf((n_x + 1.0f) / (n_y + 1.0f)) * tanf(M_PI_2_F * randu)); + float cos_phi = cosf(*phi); + float sin_phi = sinf(*phi); + *cos_theta = powf(randv, 1.0f / (n_x * cos_phi*cos_phi + n_y * sin_phi*sin_phi + 1.0f)); +} + +ccl_device int bsdf_ashikhmin_shirley_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) +{ + float3 N = sc->N; + float3 T = sc->T; + + float NdotI = dot(N, I); + if (NdotI > 0.0f) { + + float n_x = bsdf_ashikhmin_shirley_roughness_to_exponent(sc->data0); + float n_y = bsdf_ashikhmin_shirley_roughness_to_exponent(sc->data1); + + /* get x,y basis on the surface for anisotropy */ + float3 X, Y; + make_orthonormals_tangent(N, T, &X, &Y); + + /* sample spherical coords for h in tangent space */ + float phi; + float cos_theta; + if (n_x == n_y) { /* => simple isotropic sampling */ + phi = M_2PI_F * randu; + cos_theta = powf(randv, 1.0f / (n_x + 1.0f)); + } + else { /* => more complex anisotropic sampling */ + if (randu < 0.25f) { /* first quadrant */ + float remapped_randu = 4.0f * randu; + bsdf_ashikhmin_shirley_sample_first_quadrant(n_x, n_y, remapped_randu, randv, &phi, &cos_theta); + } + else if (randu < 0.5f) { /* second quadrant */ + float remapped_randu = 4.0f * (.5f - randu); + bsdf_ashikhmin_shirley_sample_first_quadrant(n_x, n_y, remapped_randu, randv, &phi, &cos_theta); + phi = M_PI_F - phi; + } + else if (randu < 0.75f) { /* third quadrant */ + float remapped_randu = 4.0f * (randu - 0.5f); + bsdf_ashikhmin_shirley_sample_first_quadrant(n_x, n_y, remapped_randu, randv, &phi, &cos_theta); + phi = M_PI_F + phi; + } + else { /* fourth quadrant */ + float remapped_randu = 4.0f * (1.0f - randu); + bsdf_ashikhmin_shirley_sample_first_quadrant(n_x, n_y, remapped_randu, randv, &phi, &cos_theta); + phi = 2.0f * M_PI_F - phi; + } + } + + /* get half vector in tangent space */ + float sin_theta = sqrtf(fmaxf(0.0f, 1.0f - cos_theta*cos_theta)); + float cos_phi = cosf(phi); + float sin_phi = sinf(phi); /* no sqrt(1-cos^2) here b/c it causes artifacts */ + float3 h = make_float3( + sin_theta * cos_phi, + sin_theta * sin_phi, + cos_theta + ); + + /* half vector to world space */ + float3 H = h.x*X + h.y*Y + h.z*N; + float HdotI = dot(H, I); + if (HdotI < 0.0f) H = -H; + + /* reflect I on H to get omega_in */ + *omega_in = -I + (2.0f * HdotI) * H; + + /* leave the rest to eval_reflect */ + /* (could maybe optimize a few things by manual inlining, but I doubt it would make much difference) */ + *eval = bsdf_ashikhmin_shirley_eval_reflect(sc, I, *omega_in, pdf); + +#ifdef __RAY_DIFFERENTIALS__ + /* just do the reflection thing for now */ + *domega_in_dx = (2.0f * dot(N, dIdx)) * N - dIdx; + *domega_in_dy = (2.0f * dot(N, dIdy)) * N - dIdy; +#endif + } + + return LABEL_REFLECT | LABEL_GLOSSY; +} + + +CCL_NAMESPACE_END + +#endif /* __BSDF_ASHIKHMIN_SHIRLEY_H__ */ |