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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_WARD_H__
#define __BSDF_WARD_H__
CCL_NAMESPACE_BEGIN
/* WARD */
__device int bsdf_ward_setup(ShaderClosure *sc)
{
sc->data0 = clamp(sc->data0, 1e-4f, 1.0f); /* m_ax */
sc->data1 = clamp(sc->data1, 1e-4f, 1.0f); /* m_ay */
sc->type = CLOSURE_BSDF_WARD_ID;
return SD_BSDF|SD_BSDF_HAS_EVAL|SD_BSDF_GLOSSY;
}
__device void bsdf_ward_blur(ShaderClosure *sc, float roughness)
{
sc->data0 = fmaxf(roughness, sc->data0); /* m_ax */
sc->data1 = fmaxf(roughness, sc->data1); /* m_ay */
}
__device float3 bsdf_ward_eval_reflect(const ShaderClosure *sc, const float3 I, const float3 omega_in, float *pdf)
{
float m_ax = sc->data0;
float m_ay = sc->data1;
float3 N = sc->N;
float3 T = sc->T;
float cosNO = dot(N, I);
float cosNI = dot(N, omega_in);
if(cosNI > 0.0f && cosNO > 0.0f) {
cosNO = max(cosNO, 1e-4f);
cosNI = max(cosNI, 1e-4f);
// get half vector and get x,y basis on the surface for anisotropy
float3 H = normalize(omega_in + I); // normalize needed for pdf
float3 X, Y;
make_orthonormals_tangent(N, T, &X, &Y);
// eq. 4
float dotx = dot(H, X) / m_ax;
float doty = dot(H, Y) / m_ay;
float dotn = dot(H, N);
float exp_arg = (dotx * dotx + doty * doty) / (dotn * dotn);
float denom = (M_4PI_F * m_ax * m_ay * sqrtf(cosNO * cosNI));
float exp_val = expf(-exp_arg);
float out = cosNI * exp_val / denom;
float oh = dot(H, I);
denom = M_4PI_F * m_ax * m_ay * oh * dotn * dotn * dotn;
*pdf = exp_val / denom;
return make_float3 (out, out, out);
}
return make_float3 (0, 0, 0);
}
__device float3 bsdf_ward_eval_transmit(const ShaderClosure *sc, const float3 I, const float3 omega_in, float *pdf)
{
return make_float3(0.0f, 0.0f, 0.0f);
}
__device int bsdf_ward_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_ax = sc->data0;
float m_ay = sc->data1;
float3 N = sc->N;
float3 T = sc->T;
float cosNO = dot(N, I);
if(cosNO > 0.0f) {
// get x,y basis on the surface for anisotropy
float3 X, Y;
make_orthonormals_tangent(N, T, &X, &Y);
// generate random angles for the half vector
// eq. 7 (taking care around discontinuities to keep
//ttoutput angle in the right quadrant)
// we take advantage of cos(atan(x)) == 1/sqrt(1+x^2)
//tttt and sin(atan(x)) == x/sqrt(1+x^2)
float alphaRatio = m_ay / m_ax;
float cosPhi, sinPhi;
if(randu < 0.25f) {
float val = 4 * randu;
float tanPhi = alphaRatio * tanf(M_PI_2_F * val);
cosPhi = 1 / sqrtf(1 + tanPhi * tanPhi);
sinPhi = tanPhi * cosPhi;
}
else if(randu < 0.5f) {
float val = 1 - 4 * (0.5f - randu);
float tanPhi = alphaRatio * tanf(M_PI_2_F * val);
// phi = M_PI_F - phi;
cosPhi = -1 / sqrtf(1 + tanPhi * tanPhi);
sinPhi = -tanPhi * cosPhi;
}
else if(randu < 0.75f) {
float val = 4 * (randu - 0.5f);
float tanPhi = alphaRatio * tanf(M_PI_2_F * val);
//phi = M_PI_F + phi;
cosPhi = -1 / sqrtf(1 + tanPhi * tanPhi);
sinPhi = tanPhi * cosPhi;
}
else {
float val = 1 - 4 * (1 - randu);
float tanPhi = alphaRatio * tanf(M_PI_2_F * val);
// phi = M_2PI_F - phi;
cosPhi = 1 / sqrtf(1 + tanPhi * tanPhi);
sinPhi = -tanPhi * cosPhi;
}
// eq. 6
// we take advantage of cos(atan(x)) == 1/sqrt(1+x^2)
//tttt and sin(atan(x)) == x/sqrt(1+x^2)
float thetaDenom = (cosPhi * cosPhi) / (m_ax * m_ax) + (sinPhi * sinPhi) / (m_ay * m_ay);
float tanTheta2 = -logf(1 - randv) / thetaDenom;
float cosTheta = 1 / sqrtf(1 + tanTheta2);
float sinTheta = cosTheta * sqrtf(tanTheta2);
float3 h; // already normalized becaused expressed from spherical coordinates
h.x = sinTheta * cosPhi;
h.y = sinTheta * sinPhi;
h.z = cosTheta;
// compute terms that are easier in local space
float dotx = h.x / m_ax;
float doty = h.y / m_ay;
float dotn = h.z;
// transform to world space
h = h.x * X + h.y * Y + h.z * N;
// generate the final sample
float oh = dot(h, I);
*omega_in = 2.0f * oh * h - I;
if(dot(Ng, *omega_in) > 0) {
float cosNI = dot(N, *omega_in);
if(cosNI > 0) {
cosNO = max(cosNO, 1e-4f);
cosNI = max(cosNI, 1e-4f);
// eq. 9
float exp_arg = (dotx * dotx + doty * doty) / (dotn * dotn);
float denom = M_4PI_F * m_ax * m_ay * oh * dotn * dotn * dotn;
*pdf = expf(-exp_arg) / denom;
// compiler will reuse expressions already computed
denom = (M_4PI_F * m_ax * m_ay * sqrtf(cosNO * cosNI));
float power = cosNI * expf(-exp_arg) / denom;
*eval = make_float3(power, power, power);
#ifdef __RAY_DIFFERENTIALS__
*domega_in_dx = (2 * dot(N, dIdx)) * N - dIdx;
*domega_in_dy = (2 * dot(N, dIdy)) * N - dIdy;
#endif
}
}
}
return LABEL_REFLECT|LABEL_GLOSSY;
}
CCL_NAMESPACE_END
#endif /* __BSDF_WARD_H__ */
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