/*
 * 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 : 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 : 0.0f;
	}
};



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

CLOSURE_PREPARE(closure_emission_prepare, GenericEmissiveClosure)

CCL_NAMESPACE_END