(****************************************
 *    NDS NeHe Lesson 03          *
 *    Author: Dovoto          *
 ****************************************)

program Lesson03;

{$mode objfpc}

uses
  ctypes, nds9;

function DrawGLScene(): boolean;
begin
  glLoadIdentity();                 // Reset The Current Modelview Matrix
  glTranslatef(-1.5,0.0,-6.0);            // Move Left 1.5 Units And Into The Screen 6.0
  glBegin(GL_TRIANGLES);                // Drawing Using Triangles
    glColor3f(1.0,0.0,0.0);           // Set The Color To Red
    glVertex3f( 0.0, 1.0, 0.0);         // Top
    glColor3f(0.0,1.0,0.0);           // Set The Color To Green
    glVertex3f(-1.0,-1.0, 0.0);         // Bottom Left
    glColor3f(0.0,0.0,1.0);           // Set The Color To Blue
    glVertex3f( 1.0,-1.0, 0.0);         // Bottom Right
  glEnd();                      // Finished Drawing The Triangle
  glTranslatef(3.0,0.0,0.0);            // Move Right 3 Units
  glColor3f(0.5,0.5,1.0);             // Set The Color To Blue One Time Only
  glBegin(GL_QUADS);                  // Draw A Quad
    glVertex3f(-1.0, 1.0, 0.0);         // Top Left
    glVertex3f( 1.0, 1.0, 0.0);         // Top Right
    glVertex3f( 1.0,-1.0, 0.0);         // Bottom Right
    glVertex3f(-1.0,-1.0, 0.0);         // Bottom Left
  glEnd();                      // Done Drawing The Quad
  result := true;                   // Keep Going
end;

var
  keys: integer;
begin
  // Setup the Main screen for 3D 
  videoSetMode(MODE_0_3D);

  glInit();

  // enable antialiasing
  glEnable(GL_ANTIALIAS);
  
  // setup the rear plane
  glClearColor(0,0,0,31); // BG must be opaque for AA to work
  glClearPolyID(63); // BG must have a unique polygon ID for AA to work
  glClearDepth($7FFF);
   
  // Set our viewport to be the same size as the screen
  glViewPort(0,0,255,191);
  

  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
  gluPerspective(70, 256.0 / 192.0, 0.1, 100);

  //ds specific, several attributes can be set here 
  glPolyFmt(POLY_ALPHA(31) or POLY_CULL_NONE);
    
  // Set the current matrix to be the model matrix
  glMatrixMode(GL_MODELVIEW);
  
  glColor3f(1, 1, 1);                 // Set the color..not in nehe source...ds gl default will be black
  
  while true do 
  begin

    DrawGLScene();
    
    // flush to screen  
    glFlush(0);

    //a handy little built in function to wait for a screen refresh
    swiWaitForVBlank();
    scanKeys();
    keys := keysDown();
    if (keys and KEY_START) <> 0 then break;    
  end;
  
end.