/*! --------------------------------------------------------------------

  \file   skybox.cpp

  \brief  Encapsulate a skybox

  \author James Kuffner
  \date   2002-09-18

// -------------------------------------------------------------------*/

#include "skybox.h"


//---------------------------------------------------------------------
//                            Skybox
//  Method:  Init
//
//! Initialize the skybox
//
//---------------------------------------------------------------------
bool Skybox::Init(const char* skyboxPath)
{
  const char* skyFiles[NUM_SKY_TEXTURES] =
  { "front.tif", "back.tif", "right.tif", "left.tif", "up.tif", "down.tif" };

  // load each texture
  for (int i = 0; i < NUM_SKY_TEXTURES; i++) {

    // set up texture load
    char imagepath[1024];
    sprintf(imagepath, "%s/%s", skyboxPath, skyFiles[i]);

    if (_skyBoxTexture[i].LoadTIFF(imagepath)) {
      // set up params and bind name
      _skyBoxTexture[i].InitTextureParams(false);
      glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
      glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
    }
  }

  return true;
}


//---------------------------------------------------------------------
//                            Skybox
//  Method:  Render
//
//! Render the skybox
//
//---------------------------------------------------------------------
bool Skybox::Render() const
{
  // constant skybox geometry
  static const GLfloat SKY_SIZE = 100.0;
  static const int NUM_VERTS = 8;
  static const GLfloat SKY_VERTS[NUM_VERTS][3] = {
    { -SKY_SIZE, -SKY_SIZE, -SKY_SIZE },
    {  SKY_SIZE, -SKY_SIZE, -SKY_SIZE },
    {  SKY_SIZE,  SKY_SIZE, -SKY_SIZE },
    { -SKY_SIZE,  SKY_SIZE, -SKY_SIZE },
    {  SKY_SIZE, -SKY_SIZE,  SKY_SIZE },
    { -SKY_SIZE, -SKY_SIZE,  SKY_SIZE },
    { -SKY_SIZE,  SKY_SIZE,  SKY_SIZE },
    {  SKY_SIZE,  SKY_SIZE,  SKY_SIZE }
  };
  static const int NUM_FACES = 6;
  static const unsigned short SKY_FACES[NUM_FACES][4] = {
    { 0, 3, 2, 1 },   // front
    { 4, 7, 6, 5 },   // back
    { 5, 6, 3, 0 },   // right
    { 1, 2, 7, 4 },   // left
    { 6, 7, 2, 3 },   // up
    { 4, 5, 0, 1 }    // down
  };

  // set up rendering attributes
  glDisable(GL_LIGHTING);
  glDisable(GL_DEPTH_WRITEMASK);
  glDisable(GL_DEPTH_TEST);
  glEnable(GL_TEXTURE_2D);
  
  // load camera transformation matrix
  GLfloat modelview[16];
  glPushMatrix();
  glGetFloatv(GL_MODELVIEW_MATRIX, modelview);

  // zero the translation part 
  modelview[12] = 0.0;
  modelview[13] = 0.0;
  modelview[14] = 0.0;
  glLoadMatrixf(modelview);

  // render all skybox faces
  glColor3f(1.0, 1.0, 1.0);
  for (int i = 0; i < NUM_FACES; i++)
  {
    // make the texture we want active
    glBindTexture(GL_TEXTURE_2D, _skyBoxTexture[i].GetName());

    // draw the quad
    glBegin(GL_QUADS);
    glTexCoord2i(0, 0);
    glVertex3fv(SKY_VERTS[SKY_FACES[i][0]]);
    glTexCoord2i(0, 1);
    glVertex3fv(SKY_VERTS[SKY_FACES[i][1]]);
    glTexCoord2i(1, 1);
    glVertex3fv(SKY_VERTS[SKY_FACES[i][2]]);
    glTexCoord2i(1, 0);
    glVertex3fv(SKY_VERTS[SKY_FACES[i][3]]);
    glEnd();
  }

  // restore rendering state
  glPopMatrix();
  glEnable(GL_LIGHTING);  
  glEnable(GL_DEPTH_TEST);
  glEnable(GL_DEPTH_WRITEMASK);

  return true;
}