/*=========================================================================

  Program:   Visualization Toolkit
  Module:    vtkOpenGLLight.cxx

  Copyright (c) Ken Martin, Will Schroeder, Bill Lorensen
  All rights reserved.
  See Copyright.txt or http://www.kitware.com/Copyright.htm for details.

     This software is distributed WITHOUT ANY WARRANTY; without even
     the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
     PURPOSE.  See the above copyright notice for more information.

=========================================================================*/
#include "vtkOpenGLLight.h"

#include "vtkOpenGLRenderer.h"
#include "vtkObjectFactory.h"
#include "vtkMatrix4x4.h"
#include "vtkOpenGLError.h"

#include "vtkOpenGL.h"

#include <cmath>

vtkStandardNewMacro(vtkOpenGLLight);

// Implement base class method.
void vtkOpenGLLight::Render(vtkRenderer *vtkNotUsed(ren), int light_index)
{
  vtkOpenGLClearErrorMacro();
  float color[4];
  float info[4];

  // get required info from light
  float dx = this->FocalPoint[0] - this->Position[0];
  float dy = this->FocalPoint[1] - this->Position[1];
  float dz = this->FocalPoint[2] - this->Position[2];

  if (this->TransformMatrix)
    {
    double mat[16];
    vtkMatrix4x4::Transpose(*this->TransformMatrix->Element, mat);

    // code assumes that we're already in GL_MODELVIEW matrix mode
    glPushMatrix();
    glMultMatrixd(mat);
    }

  color[0] = this->Intensity * this->AmbientColor[0];
  color[1] = this->Intensity * this->AmbientColor[1];
  color[2] = this->Intensity * this->AmbientColor[2];
  color[3] = 1.f;
  glLightfv(static_cast<GLenum>(light_index), GL_AMBIENT, color);

  color[0] = this->Intensity * this->DiffuseColor[0];
  color[1] = this->Intensity * this->DiffuseColor[1];
  color[2] = this->Intensity * this->DiffuseColor[2];
  glLightfv(static_cast<GLenum>(light_index), GL_DIFFUSE, color);

  color[0] = this->Intensity * this->SpecularColor[0];
  color[1] = this->Intensity * this->SpecularColor[1];
  color[2] = this->Intensity * this->SpecularColor[2];
  glLightfv(static_cast<GLenum>(light_index), GL_SPECULAR, color);

  // define the light source
  if (!this->Positional)
    {
    info[0] = -dx;
    info[1] = -dy;
    info[2] = -dz;
    info[3] = 0.f;

    glLightf(static_cast<GLenum>(light_index), GL_SPOT_EXPONENT, 0.f);
    glLightf(static_cast<GLenum>(light_index), GL_SPOT_CUTOFF, 180.f);

    glLightfv(static_cast<GLenum>(light_index), GL_POSITION, info);
    }
  else
    {
    // specify position and attenuation
    info[0] = this->Position[0];
    info[1] = this->Position[1];
    info[2] = this->Position[2];
    info[3] = 1.f;
    glLightfv(static_cast<GLenum>(light_index), GL_POSITION, info);

    glLightf(static_cast<GLenum>(light_index),
             GL_CONSTANT_ATTENUATION, this->AttenuationValues[0]);
    glLightf(static_cast<GLenum>(light_index),
             GL_LINEAR_ATTENUATION, this->AttenuationValues[1]);
    glLightf(static_cast<GLenum>(light_index),
             GL_QUADRATIC_ATTENUATION, this->AttenuationValues[2]);

    // set up spot parameters if necessary
    if (this->ConeAngle < 180.0)
      {
      info[0] = dx;
      info[1] = dy;
      info[2] = dz;
      glLightfv(static_cast<GLenum>(light_index), GL_SPOT_DIRECTION, info);
      glLightf(static_cast<GLenum>(light_index), GL_SPOT_EXPONENT,
               this->Exponent);
      glLightf(static_cast<GLenum>(light_index), GL_SPOT_CUTOFF,
               this->ConeAngle);
      }
    else
      {
      glLighti(static_cast<GLenum>(light_index), GL_SPOT_CUTOFF, 180);
      }
    }

  if (this->TransformMatrix)
    {
    glPopMatrix();
    }

  vtkOpenGLCheckErrorMacro("failed after Render");
}

//----------------------------------------------------------------------------
void vtkOpenGLLight::PrintSelf(ostream& os, vtkIndent indent)
{
  this->Superclass::PrintSelf(os, indent);
}
