/*
    This file is part of Nori, a simple educational ray tracer

    Copyright (c) 2015 by Wenzel Jakob

    Nori is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License Version 3
    as published by the Free Software Foundation.

    Nori is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program. If not, see <http://www.gnu.org/licenses/>.
*/

#pragma once

#include <nori/object.h>
#include <nori/mesh.h>

NORI_NAMESPACE_BEGIN

/**
 * \brief Superclass of all emitters
 */
class Emitter : public NoriObject {
public:

    //Sample Emitters without Mesh attached
    virtual Color3f samplePosition(const Point2f &s, EmitterSample& es) const {return Color3f();};

    /**
     * \brief Sample the Emiter
     *
     * \param scene   Scene
     * \param p       position
     * \param lp      light position
     * \param ln      light normal
     * \param pdf_dir direction of the PDF
     * \param sample  A uniformly distributed sample on \f$[0,1]^2\f$
     *
     * \return Color value
     */
    virtual Color3f sample(const Scene *scene, EmitterSample& es) const = 0;

    /**
     * \brief Returns the Color evaluated using the light normal and the light to interection path
     *
     * \param its    light intersection
     */
    virtual Color3f eval(const Intersection &its) const = 0;


        /**
     * \brief Returns the PDF using the light normal and the light to interection path
     * \param lti   ray
     */
    virtual float pdf(const Vector3f &lti) const = 0;


    /**
     * \brief Return the type of object (i.e. Mesh/Emitter/etc.) 
     * provided by this instance
     * */
    EClassType getClassType() const { return EEmitter; }
};

NORI_NAMESPACE_END