text: /**************************************************************************\
   *
   *  This file is part of the Coin 3D visualization library.
   *  Copyright (C) by Kongsberg Oil & Gas Technologies.
   *
   *  This library is free software; you can redistribute it and/or
   *  modify it under the terms of the GNU General Public License
   *  ("GPL") version 2 as published by the Free Software Foundation.
   *  See the file LICENSE.GPL at the root directory of this source
   *  distribution for additional information about the GNU GPL.
   *
   *  For using Coin with software that can not be combined with the GNU
   *  GPL, and for taking advantage of the additional benefits of our
   *  support services, please contact Kongsberg Oil & Gas Technologies
   *  about acquiring a Coin Professional Edition License.
   *
   *  See http://www.coin3d.org/ for more information.
   *
   *  Kongsberg Oil & Gas Technologies, Bygdoy Alle 5, 0257 Oslo, NORWAY.
   *  http://www.sim.no/  sales@sim.no  coin-support@coin3d.org
   *
  \**************************************************************************/
  
  /*!
    \class SoLight SoLight.h Inventor/nodes/SoLight.h
    \brief The SoLight class is the base class for light emitting nodes.
    \ingroup nodes
  
    This node type is abstract and does not in itself provide any light
    sources to the scene, you need to use one of its subclasses.
  
    There are a few important things to know about light sources in
    Coin. First of all, the more light sources you have in your scene,
    the slower the rendering will be. The impact on rendering speed is
    highly dependent on the graphics hardware and/or rendering subsystem
    software implementation (i.e. how optimized an OpenGL you or your
    users are running), but it could be severe.
  
    Another issue which is important to know is that OpenGL rendering
    engines usually have a fixed maximum number of available light
    sources which can be present in the state at the same time. If you
    reach the maximum number, further light sources will simply be
    ignored. The maximum number of light sources for OpenGL rendering
    can be found by using:
  
    \code
        #include <Inventor/elements/SoGLLightIdElement.h>
  #include <Inventor/nodes/SoSubNodeP.h>
        // ...[snip]...
        int nrlights = SoGLLightIdElement::getMaxGLSources();
    \endcode
  
    If you are clever with how you use light sources, you can get away
    with using a lot more lights in a scene graph than the max available
    from the rendering system. This is because light sources are stacked
    on the traversal state, just like other appearance data. So if you
    put light sources under SoSeparator nodes, they will be popped off
    and "forgotten" for the remaining geometry of the scene graph after
    the subgraph below an SoSeparator has been traversed.
  */
  
  #include <Inventor/nodes/SoLight.h>
  
  #include <Inventor/actions/SoCallbackAction.h>
  #include <Inventor/actions/SoGLRenderAction.h>
  #include <Inventor/elements/SoGLLightIdElement.h>
  #include <Inventor/elements/SoLightAttenuationElement.h>
  #include <Inventor/elements/SoLightElement.h>
  #include <Inventor/elements/SoModelMatrixElement.h>
  #include <Inventor/elements/SoViewingMatrixElement.h>
  
  #include "nodes/SoSubNodeP.h"
  
  /*!
    \var SoSFBool SoLight::on
  
    Whether light source should be on or off. The on-flag defaults to \c
    TRUE.
  */
  /*!
    \var SoSFFloat SoLight::intensity
  
    Intensity of light source. This decides how much the light source
    should affect the colors etc of the scene geometry. Valid range is
    0.0 (none) to 1.0 (maximum). Default value is 1.0.
  */
  /*!
    \var SoSFColor SoLight::color
  
    Color of light source. Default is an all-white light source.
  */
  
  
  SO_NODE_ABSTRACT_SOURCE(SoLight);
  
  /*!
    Constructor.
  */
  SoLight::SoLight(void)
  {
    SO_NODE_INTERNAL_CONSTRUCTOR(SoLight);
  
    SO_NODE_ADD_FIELD(on, (TRUE));
    SO_NODE_ADD_FIELD(intensity, (1.0f));
    SO_NODE_ADD_FIELD(color, (SbColor(1.0f, 1.0f, 1.0f)));
  }
  
  /*!
    Destructor.
  */
  SoLight::~SoLight()
  {
  }
  
  // Doc from superclass.
  void
  SoLight::initClass(void)
  {
    SO_NODE_INTERNAL_INIT_ABSTRACT_CLASS(SoLight, SO_FROM_INVENTOR_1);
  
    SO_ENABLE(SoGLRenderAction, SoLightAttenuationElement);
    SO_ENABLE(SoGLRenderAction, SoGLLightIdElement);
    SO_ENABLE(SoGLRenderAction, SoLightElement);
  
    SO_ENABLE(SoCallbackAction, SoLightAttenuationElement);
    SO_ENABLE(SoCallbackAction, SoLightElement);
  }
  
  // Doc from superclass.
  void
  SoLight::callback(SoCallbackAction * action)
  {
    SoState * state = action->getState();
    SoLightElement::add(state, this, (SoModelMatrixElement::get(state) * 
                                      SoViewingMatrixElement::get(state)));
  }
  