void setup()
{
  size(screen.width, screen.height, OPENGL);
  //  size(screenWidth, screenHeight, OPENGL);  // fullscreen
  // frameRate(3000);
  pgl = (PGraphicsOpenGL) g;
  gl = pgl.gl;
  hint(DISABLE_DEPTH_TEST);
  gl.glDepthMask(false);
  gl.glDisable(GL.GL_DEPTH_TEST);
  loadSkybox(skyboxName, ".jpg"); //   loadSkybox(skyboxName, ".png");
  pgl.beginGL();
  skybox = gl.glGenLists(1);
  gl.glNewList(skybox, GL.GL_COMPILE);
  stroke(312,0,0);  // comment it to see NO cube edges
  //noStroke();  // comment it to see cube edges
  //gl.glFrontFace(GL.GL_CCW);
  // gl.glEnable(GL.GL_CULL_FACE);
  TexturedCube();
  gl.glDisable(GL.GL_CULL_FACE);
  gl.glEndList();
  pgl.endGL();
  float fov = PI/3.0;
  float cameraZ = (height/2.0) / tan(fov/2.0);
  perspective(fov, float(width)/float(height), cameraZ/10.0, cameraZ*100.0);
  cam = new PeasyCam(this, width);
  cam.setResetOnDoubleClick(false);
  cam.setMinimumDistance(10);
  cam.setMaximumDistance(width*10);
  // gl.glEnable(GL.GL_CULL_FACE);
}

void draw()
{
  background(255);
  pgl.beginGL();
  gl.glCallList( skybox );
  pgl.endGL();
  //translate(width/2.0, height/2.0, -100);
  println("FPS: "+ frameRate);
}

float p = 400;   // half skybox size
float m = 200 ; // -p;

// create cube edges
PVector P000 = new PVector (m,m,m);
PVector P010 = new PVector (m,p,m);
PVector P110 = new PVector (p,p,m);
PVector P100 = new PVector (p,m,m);
PVector P001 = new PVector (m,m,p);
PVector P011 = new PVector (m,p,p);
PVector P111 = new PVector (p,p,p);
PVector P101 = new PVector (p,m,p);

Texture tex1,tex2,tex3,tex4,tex5,tex6;   // texture images

// load six skybox images as cube texture

void loadSkybox(String skyboxName, String fExt)

{

  try {

    tex1 = TextureIO.newTexture(new File(dataPath(skyboxName + "_front" + fExt)), true);

    tex2 = TextureIO.newTexture(new File(dataPath(skyboxName + "_front" + fExt)), true);

    tex3 = TextureIO.newTexture(new File(dataPath(skyboxName + "_front" + fExt)), true);

    tex4 = TextureIO.newTexture(new File(dataPath(skyboxName + "_front" + fExt)), true);

    tex5 = TextureIO.newTexture(new File(dataPath(skyboxName + "_front" + fExt)), true);

    tex6 = TextureIO.newTexture(new File(dataPath(skyboxName + "_front" + fExt)), true);
  }

  catch (IOException e) {   

    println( e);
    exit();
  }

  //textureMode(NORMALIZED);
}

// Assign six texture to the six cube faces

void TexturedCube()

{

  TexturedCubeSide (P100, P000, P010, P110, tex1);   // -Z "front" face

  TexturedCubeSide (P001, P101, P111, P011, tex2);   // +Z "back" face

  TexturedCubeSide (P000, P001, P011, P010, tex3);   // -X "left" face

  TexturedCubeSide (P101, P100, P110, P111, tex4);   // +X "right" face

  TexturedCubeSide (P110, P010, P011, P111, tex5);   // +Y "base" face

  TexturedCubeSide (P101, P001, P000, P100, tex6);   // -Y "top" face
}

// create a cube side given by 4 edge vertices and a texture

void TexturedCubeSide(PVector P1, PVector P2, PVector P3, PVector P4, Texture tex)
{

  //gl.glutSolidCube(74.2);

  tex.enable();
  tex.bind();

  gl.glBegin(GL.GL_QUADS);

  gl.glTexCoord2f(1.0f, 0.0f);

  gl.glVertex3f(P1.x, P1.y, P1.z);

  gl.glTexCoord2f(0.0f, 0.0f);

  gl.glVertex3f(P2.x, P2.y, P2.z);

  gl.glTexCoord2f(0.0f, 1.0f);

  gl.glVertex3f(P3.x, P3.y, P3.z);

  gl.glTexCoord2f(1.0f, 1.0f);

  gl.glVertex3f(P4.x, P4.y, P4.z);

  gl.glEnd();

  tex.disable();
}