blender/intern/cycles/kernel/osl/bsdf_ward.cpp
Ton Roosendaal da376e0237 Cycles render engine, initial commit. This is the engine itself, blender modifications and build instructions will follow later.
Cycles uses code from some great open source projects, many thanks them:

* BVH building and traversal code from NVidia's "Understanding the Efficiency of Ray Traversal on GPUs":
http://code.google.com/p/understanding-the-efficiency-of-ray-traversal-on-gpus/
* Open Shading Language for a large part of the shading system:
http://code.google.com/p/openshadinglanguage/
* Blender for procedural textures and a few other nodes.
* Approximate Catmull Clark subdivision from NVidia Mesh tools:
http://code.google.com/p/nvidia-mesh-tools/
* Sobol direction vectors from:
http://web.maths.unsw.edu.au/~fkuo/sobol/
* Film response functions from:
http://www.cs.columbia.edu/CAVE/software/softlib/dorf.php
2011-04-27 11:58:34 +00:00

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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.
*/
#include <OpenImageIO/fmath.h>
#include <OSL/genclosure.h>
#include "osl_closures.h"
#include "util_math.h"
CCL_NAMESPACE_BEGIN
using namespace OSL;
// anisotropic ward - leaks energy at grazing angles
// see http://www.graphics.cornell.edu/~bjw/wardnotes.pdf
class WardClosure : public BSDFClosure {
public:
Vec3 m_N;
Vec3 m_T;
float m_ax, m_ay;
WardClosure() : BSDFClosure(Labels::GLOSSY) { }
void setup()
{
m_ax = clamp(m_ax, 1e-5f, 1.0f);
m_ay = clamp(m_ay, 1e-5f, 1.0f);
}
bool mergeable (const ClosurePrimitive *other) const {
const WardClosure *comp = (const WardClosure *)other;
return m_N == comp->m_N && m_T == comp->m_T &&
m_ax == comp->m_ax && m_ay == comp->m_ay &&
BSDFClosure::mergeable(other);
}
size_t memsize () const { return sizeof(*this); }
const char *name () const { return "ward"; }
void print_on (std::ostream &out) const {
out << name() << " ((";
out << m_N[0] << ", " << m_N[1] << ", " << m_N[2] << "), (";
out << m_T[0] << ", " << m_T[1] << ", " << m_T[2] << "), ";
out << m_ax << ", " << m_ay << ")";
}
float albedo (const Vec3 &omega_out) const
{
return 1.0f;
}
Color3 eval_reflect (const Vec3 &omega_out, const Vec3 &omega_in, float& pdf) const
{
float cosNO = m_N.dot(omega_out);
float cosNI = m_N.dot(omega_in);
if (cosNI > 0 && cosNO > 0) {
// get half vector and get x,y basis on the surface for anisotropy
Vec3 H = omega_in + omega_out;
H.normalize(); // normalize needed for pdf
Vec3 X, Y;
make_orthonormals(m_N, m_T, X, Y);
// eq. 4
float dotx = H.dot(X) / m_ax;
float doty = H.dot(Y) / m_ay;
float dotn = H.dot(m_N);
float exp_arg = (dotx * dotx + doty * doty) / (dotn * dotn);
float denom = (4 * (float) M_PI * m_ax * m_ay * sqrtf(cosNO * cosNI));
float exp_val = expf(-exp_arg);
float out = cosNI * exp_val / denom;
float oh = H.dot(omega_out);
denom = 4 * (float) M_PI * m_ax * m_ay * oh * dotn * dotn * dotn;
pdf = exp_val / denom;
return Color3 (out, out, out);
}
return Color3 (0, 0, 0);
}
Color3 eval_transmit (const Vec3 &omega_out, const Vec3 &omega_in, float& pdf) const
{
return Color3 (0, 0, 0);
}
ustring sample (const Vec3 &Ng,
const Vec3 &omega_out, const Vec3 &domega_out_dx, const Vec3 &domega_out_dy,
float randu, float randv,
Vec3 &omega_in, Vec3 &domega_in_dx, Vec3 &domega_in_dy,
float &pdf, Color3 &eval) const
{
float cosNO = m_N.dot(omega_out);
if (cosNO > 0) {
// get x,y basis on the surface for anisotropy
Vec3 X, Y;
make_orthonormals(m_N, m_T, X, Y);
// generate random angles for the half vector
// eq. 7 (taking care around discontinuities to keep
// output angle in the right quadrant)
// we take advantage of cos(atan(x)) == 1/sqrt(1+x^2)
// 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((float) M_PI_2 * val);
cosPhi = 1 / sqrtf(1 + tanPhi * tanPhi);
sinPhi = tanPhi * cosPhi;
} else if (randu < 0.5) {
float val = 1 - 4 * (0.5f - randu);
float tanPhi = alphaRatio * tanf((float) M_PI_2 * val);
// phi = (float) M_PI - 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((float) M_PI_2 * val);
//phi = (float) M_PI + phi;
cosPhi = -1 / sqrtf(1 + tanPhi * tanPhi);
sinPhi = tanPhi * cosPhi;
} else {
float val = 1 - 4 * (1 - randu);
float tanPhi = alphaRatio * tanf((float) M_PI_2 * val);
// phi = 2 * (float) M_PI - phi;
cosPhi = 1 / sqrtf(1 + tanPhi * tanPhi);
sinPhi = -tanPhi * cosPhi;
}
// eq. 6
// we take advantage of cos(atan(x)) == 1/sqrt(1+x^2)
// 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);
Vec3 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 * m_N;
// generate the final sample
float oh = h.dot(omega_out);
omega_in.x = 2 * oh * h.x - omega_out.x;
omega_in.y = 2 * oh * h.y - omega_out.y;
omega_in.z = 2 * oh * h.z - omega_out.z;
if (Ng.dot(omega_in) > 0) {
float cosNI = m_N.dot(omega_in);
if (cosNI > 0) {
// eq. 9
float exp_arg = (dotx * dotx + doty * doty) / (dotn * dotn);
float denom = 4 * (float) M_PI * m_ax * m_ay * oh * dotn * dotn * dotn;
pdf = expf(-exp_arg) / denom;
// compiler will reuse expressions already computed
denom = (4 * (float) M_PI * m_ax * m_ay * sqrtf(cosNO * cosNI));
float power = cosNI * expf(-exp_arg) / denom;
eval.setValue(power, power, power);
domega_in_dx = (2 * m_N.dot(domega_out_dx)) * m_N - domega_out_dx;
domega_in_dy = (2 * m_N.dot(domega_out_dy)) * m_N - domega_out_dy;
/* disabled for now - gives texture filtering problems */
#if 0
// Since there is some blur to this reflection, make the
// derivatives a bit bigger. In theory this varies with the
// roughness but the exact relationship is complex and
// requires more ops than are practical.
domega_in_dx *= 10;
domega_in_dy *= 10;
#endif
}
}
}
return Labels::REFLECT;
}
};
ClosureParam bsdf_ward_params[] = {
CLOSURE_VECTOR_PARAM(WardClosure, m_N),
CLOSURE_VECTOR_PARAM(WardClosure, m_T),
CLOSURE_FLOAT_PARAM (WardClosure, m_ax),
CLOSURE_FLOAT_PARAM (WardClosure, m_ay),
CLOSURE_STRING_KEYPARAM("label"),
CLOSURE_FINISH_PARAM(WardClosure) };
CLOSURE_PREPARE(bsdf_ward_prepare, WardClosure)
CCL_NAMESPACE_END