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/*
* Adapted from Open Shading Language with this license:
*
* Copyright (c) 2009-2010 Sony Pictures Imageworks Inc., et al.
* All Rights Reserved.
*
* Modifications Copyright 2011, Blender Foundation.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met:
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* * Neither the name of Sony Pictures Imageworks nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#ifndef __BSDF_ASHIKHMIN_VELVET_H__
#define __BSDF_ASHIKHMIN_VELVET_H__
CCL_NAMESPACE_BEGIN
ccl_device int bsdf_ashikhmin_velvet_setup(ShaderClosure *sc)
{
float sigma = fmaxf(sc->data0, 0.01f);
sc->data0 = 1.0f/(sigma * sigma); /* m_invsigma2 */
sc->type = CLOSURE_BSDF_ASHIKHMIN_VELVET_ID;
return SD_BSDF|SD_BSDF_HAS_EVAL;
}
ccl_device float3 bsdf_ashikhmin_velvet_eval_reflect(const ShaderClosure *sc, const float3 I, const float3 omega_in, float *pdf)
{
float m_invsigma2 = sc->data0;
float3 N = sc->N;
float cosNO = dot(N, I);
float cosNI = dot(N, omega_in);
if(cosNO > 0 && cosNI > 0) {
float3 H = normalize(omega_in + I);
float cosNH = dot(N, H);
float cosHO = fabsf(dot(I, H));
if(!(fabsf(cosNH) < 1.0f-1e-5f && cosHO > 1e-5f))
return make_float3(0.0f, 0.0f, 0.0f);
float cosNHdivHO = cosNH / cosHO;
cosNHdivHO = fmaxf(cosNHdivHO, 1e-5f);
float fac1 = 2 * fabsf(cosNHdivHO * cosNO);
float fac2 = 2 * fabsf(cosNHdivHO * cosNI);
float sinNH2 = 1 - cosNH * cosNH;
float sinNH4 = sinNH2 * sinNH2;
float cotangent2 = (cosNH * cosNH) / sinNH2;
float D = expf(-cotangent2 * m_invsigma2) * m_invsigma2 * M_1_PI_F / sinNH4;
float G = min(1.0f, min(fac1, fac2)); // TODO: derive G from D analytically
float out = 0.25f * (D * G) / cosNO;
*pdf = 0.5f * M_1_PI_F;
return make_float3(out, out, out);
}
return make_float3(0.0f, 0.0f, 0.0f);
}
ccl_device float3 bsdf_ashikhmin_velvet_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 int bsdf_ashikhmin_velvet_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)
{
float m_invsigma2 = sc->data0;
float3 N = sc->N;
// we are viewing the surface from above - send a ray out with uniform
// distribution over the hemisphere
sample_uniform_hemisphere(N, randu, randv, omega_in, pdf);
if(dot(Ng, *omega_in) > 0) {
float3 H = normalize(*omega_in + I);
float cosNI = dot(N, *omega_in);
float cosNO = dot(N, I);
float cosNH = dot(N, H);
float cosHO = fabsf(dot(I, H));
if(fabsf(cosNO) > 1e-5f && fabsf(cosNH) < 1.0f-1e-5f && cosHO > 1e-5f) {
float cosNHdivHO = cosNH / cosHO;
cosNHdivHO = fmaxf(cosNHdivHO, 1e-5f);
float fac1 = 2 * fabsf(cosNHdivHO * cosNO);
float fac2 = 2 * fabsf(cosNHdivHO * cosNI);
float sinNH2 = 1 - cosNH * cosNH;
float sinNH4 = sinNH2 * sinNH2;
float cotangent2 = (cosNH * cosNH) / sinNH2;
float D = expf(-cotangent2 * m_invsigma2) * m_invsigma2 * M_1_PI_F / sinNH4;
float G = min(1.0f, min(fac1, fac2)); // TODO: derive G from D analytically
float power = 0.25f * (D * G) / cosNO;
*eval = make_float3(power, power, power);
#ifdef __RAY_DIFFERENTIALS__
// TODO: find a better approximation for the retroreflective bounce
*domega_in_dx = (2 * dot(N, dIdx)) * N - dIdx;
*domega_in_dy = (2 * dot(N, dIdy)) * N - dIdy;
#endif
}
else
*pdf = 0.0f;
}
else
*pdf = 0.0f;
return LABEL_REFLECT|LABEL_DIFFUSE;
}
CCL_NAMESPACE_END
#endif /* __BSDF_ASHIKHMIN_VELVET_H__ */
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