/*
 * 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"

CCL_NAMESPACE_BEGIN

using namespace OSL;

/// Variable cone emissive closure
///
/// This primitive emits in a cone having a configurable
/// penumbra area where the light decays to 0 reaching the
/// outer_angle limit. It can also behave as a lambertian emitter
/// if the provided angles are PI/2, which is the default
///
class GenericEmissiveClosure : public EmissiveClosure {
public:
    GenericEmissiveClosure() { }

    void setup() { }

    size_t memsize () const { return sizeof(*this); }

    const char *name () const { return "emission"; }

    void print_on (std::ostream &out) const {
        out << name() << "()";
    }

    Color3 eval (const Vec3 &Ng, const Vec3 &omega_out) const
    {
        float cosNO = fabsf(Ng.dot(omega_out));
        float res = cosNO > 0 ? 1.0f / float(M_PI) : 0.0f;
        return Color3(res, res, res);
    }

    void sample (const Vec3 &Ng, float randu, float randv,
                 Vec3 &omega_out, float &pdf) const
    {
        // We don't do anything sophisticated here for the step
        // We just sample the whole cone uniformly to the cosine
        Vec3 T, B;
        make_orthonormals(Ng, T, B);
        float phi = 2 * (float) M_PI * randu;
        float cosTheta = sqrtf(1.0f - 1.0f * randv);
        float sinTheta = sqrtf(1.0f - cosTheta * cosTheta);
        omega_out = (cosf(phi) * sinTheta) * T +
                    (sinf(phi) * sinTheta) * B +
                                 cosTheta  * Ng;
        pdf = 1.0f / float(M_PI);
    }

    /// Return the probability distribution function in the direction omega_out,
    /// given the parameters and the light's surface normal.  This MUST match
    /// the PDF computed by sample().
    float pdf (const Vec3 &Ng,
               const Vec3 &omega_out) const
    {
        float cosNO = Ng.dot(omega_out);
        return cosNO > 0 ? 1.0f / float(M_PI) : 0.0f;
    }
};



ClosureParam closure_emission_params[] = {
    CLOSURE_STRING_KEYPARAM("label"),
    CLOSURE_FINISH_PARAM(GenericEmissiveClosure) };

CLOSURE_PREPARE(closure_emission_prepare, GenericEmissiveClosure)

CCL_NAMESPACE_END

