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/*!
  \class SoSpotLight SoSpotLight.h Inventor/nodes/SoSpotLight.h
  \brief The SoSpotLight class is a node type for light sources with a cone shaped lightvolume.
  \ingroup nodes

  Spotlights are light sources with a position and a direction. They
  can be thought of as a pointlight with a lampshade.

  See also documentation of parent class for important information
  regarding light sources in general.

  <b>FILE FORMAT/DEFAULTS:</b>
  \code
    SpotLight {
        on TRUE
        intensity 1
        color 1 1 1
        location 0 0 1
        direction 0 0 -1
        dropOffRate 0
        cutOffAngle 0.78539819
    }
  \endcode

  \sa SoSpotLight
*/

// *************************************************************************

#include <Inventor/nodes/SoSpotLight.h>
#include <Inventor/nodes/SoSubNodeP.h>

#include <Inventor/SbColor4f.h>
#include <Inventor/SbVec4f.h>
#include <Inventor/actions/SoGLRenderAction.h>
#include <Inventor/elements/SoEnvironmentElement.h>
#include <Inventor/elements/SoGLLightIdElement.h>
#include <Inventor/elements/SoModelMatrixElement.h>
#include <Inventor/elements/SoViewingMatrixElement.h>
#include <Inventor/elements/SoLightElement.h>
#include <Inventor/errors/SoDebugError.h>

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif // HAVE_CONFIG_H
#include <Inventor/system/gl.h>

// *************************************************************************

/*!
  \var SoSFVec3f SoSpotLight::location

  3D position of light source. Default position is <0, 0, 1>.
*/
/*!
  \var SoSFVec3f SoSpotLight::direction

  Direction vector, where the light is pointing. Default is to point
  along the negative z-axis.
*/
/*!
  \var SoSFFloat SoSpotLight::dropOffRate

  The rate of intensity drop-off from the ray along the direction
  vector. Value must be between 0.0 (equal intensity for the whole
  cone of light), to 1.0 (a narrow intensity ray).

  Default value is 0.0.
*/
/*!
  \var SoSFFloat SoSpotLight::cutOffAngle

  The angle in radians from the direction vector where there will be
  no light outside (i.e. the angle of the "lampshade"). Default value
  is PI/4.0 (i.e. 45°).
*/


// *************************************************************************

SO_NODE_SOURCE(SoSpotLight);

// *************************************************************************

/*!
  Constructor.
*/
SoSpotLight::SoSpotLight(void)
{
  SO_NODE_INTERNAL_CONSTRUCTOR(SoSpotLight);

  SO_NODE_ADD_FIELD(location, (0.0f, 0.0f, 1.0f));
  SO_NODE_ADD_FIELD(direction, (0.0f, 0.0f, -1.0f));
  SO_NODE_ADD_FIELD(dropOffRate, (0.0f));
  SO_NODE_ADD_FIELD(cutOffAngle, (float(M_PI)/4.0f));
}

/*!
  Destructor.
*/
SoSpotLight::~SoSpotLight()
{
}

// Doc in superclass.
void
SoSpotLight::initClass(void)
{
  SO_NODE_INTERNAL_INIT_CLASS(SoSpotLight, SO_FROM_INVENTOR_1|SoNode::VRML1);
}

// Doc in superclass.
void
SoSpotLight::GLRender(SoGLRenderAction * action)
{
  if (!this->on.getValue()) return;

  SoState * state = action->getState();
  int idx = SoGLLightIdElement::increment(state);

  if (idx < 0) {
#if COIN_DEBUG
    SoDebugError::post("SoSpotLight::GLRender()",
                       "Max # lights exceeded :(\n");
#endif // COIN_DEBUG
    return;
  }

  SoLightElement::add(state, this, SoModelMatrixElement::get(state) *
                      SoViewingMatrixElement::get(state));
  
  GLenum light = (GLenum) (idx + GL_LIGHT0);

  SbVec3f attenuation = SoEnvironmentElement::getLightAttenuation(state);

  glLightf(light, GL_QUADRATIC_ATTENUATION, attenuation[0]);
  glLightf(light, GL_LINEAR_ATTENUATION, attenuation[1]);
  glLightf(light, GL_CONSTANT_ATTENUATION, attenuation[2]);

  SbColor4f lightcolor(0.0f, 0.0f, 0.0f, 1.0f);
  // disable ambient contribution from this light source
  glLightfv(light, GL_AMBIENT, lightcolor.getValue());
  lightcolor.setRGB(this->color.getValue());
  lightcolor *= this->intensity.getValue();

  glLightfv(light, GL_DIFFUSE, lightcolor.getValue());
  glLightfv(light, GL_SPECULAR, lightcolor.getValue());

  SbVec3f loc = this->location.getValue();

  // point (or spot) light when w = 1.0
  SbVec4f posvec(loc[0], loc[1], loc[2], 1.0f);
  glLightfv(light, GL_POSITION, posvec.getValue());
  glLightfv(light, GL_SPOT_DIRECTION, this->direction.getValue().getValue());

  float cutoff = this->cutOffAngle.getValue() * 180.0f / float(M_PI);
  float dropoff = this->dropOffRate.getValue() * 128.0f;

  glLightf(light, GL_SPOT_EXPONENT, dropoff);
  glLightf(light, GL_SPOT_CUTOFF, cutoff);
}
