Course 3D_OpenGL: 3D-Graphics with C++ and OpenGL Chapter 1: Moving Triangles Copyright © by V. Miszalok, last update: 2011-03-20
Let me know what you think	Project triangle1   Animation   Three Triangles   Hundred Triangles

This project is the OpenGL-clone of the C#-projects:
3D-Computer Graphics with XNA, Chapter C1: Moving Triangles and of
3D-Computer Graphics with Managed DirectX, Chapter C1: Moving Triangles.

Project triangle1

Start Visual C++ 2010 Express:
File → New → Project → Win32 Project → Name: triangle1 → Location: C:\temp → uncheck Create directory for solution → Win 32 Application Wizard - triangle1 → Application Settings → Application type: Windows application → Additional options: Empty project → quit with button Finish.

In the Solution Explorer - window Right-click triangle1. A drop-down menu appears with a branch: "Add". Click Add → Existing item... → C:\Program Files\Microsoft SDKs\Windows\v7.0A\Lib\OpenGl32.Lib → Quit with button Add.
(If you don't find OpenGl32.Lib download opengl32.lib and gl.h.)
Check whether OpenGl32.Lib arrived in the Solution Explorer tree.

In the Solution Explorer - window click the + sign in front of triangle1.
A tree appears with a branch: "Source Files". Right-click Source Files. A drop-down menu appears. Click Add → New Item... → Add New item - triangle1 → Visual Studio installed templates: C++ File (.cpp) → Name: triangle1 → Location: c:\Temp\triangle1 → Quit with button Add.
Check whether triangle1.cpp arrived under branch Source Files in the Solution Explorer tree.

If the Solution Explorer - window is invisible, open it via the main menu: View → Solution Explorer.

Copy the following code into the empty source file triangle1.cpp:

#include <windows.h>
#include <time.h>
#include <C:\Program Files\Microsoft SDKs\Windows\v7.0A\include\gl\Gl.h> //adjust path to your Gl.h !

LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam);
HWND     hWnd;
HDC      hDC;
HGLRC    hRC;

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int iCmdShow)
{ WNDCLASS wc;
  wc.style         = CS_OWNDC;
  wc.style         = CS_HREDRAW | CS_VREDRAW;
  wc.lpfnWndProc   = WndProc;
  wc.cbClsExtra    = wc.cbWndExtra = 0;
  wc.hInstance     = hInstance;
  wc.hIcon         = LoadIcon( NULL, IDI_APPLICATION );
  wc.hCursor       = LoadCursor( NULL, IDC_ARROW );
  wc.hbrBackground = (HBRUSH)GetStockObject( BLACK_BRUSH );
  wc.lpszMenuName  = NULL;
  wc.lpszClassName = L"ogl1";
  RegisterClass( &wc );
  hWnd = CreateWindow( wc.lpszClassName, L"C++ OpenGL Chapter 1", 
                       WS_CAPTION | WS_POPUPWINDOW | WS_VISIBLE,
                       0, 0, 300, 300, NULL, NULL, hInstance, NULL );
  hDC = GetDC( hWnd );
  PIXELFORMATDESCRIPTOR pfd;
  ZeroMemory( &pfd, sizeof( pfd ) );
  pfd.nSize      = sizeof( pfd );
  pfd.nVersion   = 1;
  pfd.dwFlags    = PFD_DRAW_TO_WINDOW | PFD_SUPPORT_OPENGL | PFD_DOUBLEBUFFER;
  pfd.iPixelType = PFD_TYPE_RGBA;
  pfd.cColorBits = 24;
  pfd.cDepthBits = 16;
  pfd.iLayerType = PFD_MAIN_PLANE;
  int format = ChoosePixelFormat( hDC, &pfd );
  SetPixelFormat( hDC, format, &pfd );
  hRC = wglCreateContext( hDC );
  wglMakeCurrent( hDC, hRC );
  GLfloat vertex[] = {-0.5f,-0.5f, 0.0f,  //lower left  vertex
                       0.0f, 0.5f, 0.0f,  //mid   peek  vertex
                       0.5f,-0.5f, 0.0f };//lower right vertex
  GLfloat color[]  = { 0.0f, 0.0f, 1.0f,  //blue
                       0.0f, 1.0f, 0.0f,  //green
                       1.0f, 0.0f, 0.0f };//red
  glVertexPointer( 3, GL_FLOAT, 0, vertex );
  glColorPointer ( 3, GL_FLOAT, 0, color );
  glEnableClientState( GL_VERTEX_ARRAY );
  glEnableClientState( GL_COLOR_ARRAY  );
 
  glClearColor( 0.0f, 0.0f, 0.0f, 0.0f );
  glClear( GL_COLOR_BUFFER_BIT );

  glLoadIdentity(); //erase all former transforms
  glDrawArrays( GL_TRIANGLES, 0, 3 ); //draw it
  SwapBuffers( hDC );                 //show it

  MSG msg;
  while ( TRUE ) //infinite message listening
  { if ( PeekMessage( &msg, NULL, 0, 0, PM_REMOVE ) )
    { if ( msg.message == WM_QUIT ) return 0; //stop infinite loop
      TranslateMessage( &msg ); 
      DispatchMessage ( &msg ); 
    } 
  } //end of infinite loop
}   //end of WinMain

LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{ switch (message)
  { case WM_CLOSE: PostQuitMessage( 0 ); return 0; //send WM_QUIT to stop infinite loop
    case WM_QUIT : wglMakeCurrent( hDC, NULL );    //disconnect hRC from hDC
                   wglDeleteContext( hRC );        //say goodbye to hRC
                   ReleaseDC( hWnd, hDC );         //say goodbye to hDC
                   DestroyWindow( hWnd ); return 0;//say goodbye to hWnd
    default      : return DefWindowProc( hWnd, message, wParam, lParam );
  }
}

Click Debug → Start Without Debugging Ctrl F5.

Experiments: (Debug → Start Without Debugging Ctrl F5 after any change.)

Animation

Delete the tail of the WinMain-procedure below glEnableClientState( GL_COLOR_ARRAY ); and its last bracket } //end of WinMain and replace the lines:

  glClearColor( 0.0f, 0.0f, 0.0f, 0.0f );
  .
  .
  .
  } //end of infinite loop

by

  float rot = 0.0f; 
  MSG msg;
  while ( TRUE ) //infinite loop
  { glClearColor( 0.0f, 0.0f, 0.0f, 0.0f );
    glClear( GL_COLOR_BUFFER_BIT );
    glLoadIdentity(); //erase all former transforms
    glRotatef( rot+=0.01f, 0.0f, 0.0f, 1.0f ); 
    glDrawArrays( GL_TRIANGLES, 0, 3 ); //draw it
    SwapBuffers( hDC );                 //show it

    if ( PeekMessage( &msg, NULL, 0, 0, PM_REMOVE ) )
    { if ( msg.message == WM_QUIT ) return 0; //stop infinite loop
      TranslateMessage( &msg ); 
      DispatchMessage ( &msg ); 
    } 
  } //end of infinite loop

Experiments: (Debug → Start Without Debugging Ctrl F5 after any change.)

Three Triangles

Change the while ( TRUE ) //infinite loop until il looks like this:

  while ( TRUE ) //infinite loop
  { glClearColor( 0.0f, 0.0f, 0.0f, 0.0f );
    glClear( GL_COLOR_BUFFER_BIT );
    glLoadIdentity(); //erase all former transforms
    glRotatef( rot+=0.1f, 0.0f, 0.0f, 1.0f );
    glDrawArrays( GL_TRIANGLES, 0, 3 ); //draw it in the middle
    glScalef    ( 0.7f, 0.7f, 0.7f );   //zoom it down
    glTranslatef( -1.0f, 0.0f, 0.0f );  //shift it to the left side
    glDrawArrays( GL_TRIANGLES, 0, 3 ); //draw it again
    glTranslatef( 2.0f, 0.0f, 0.0f );   //shift it to the right side
    glDrawArrays( GL_TRIANGLES, 0, 3 ); //draw it again
    SwapBuffers( hDC );                 //show it

    if ( PeekMessage( &msg, NULL, 0, 0, PM_REMOVE ) )
    { if ( msg.message == WM_QUIT ) return 0; //stop infinite loop
      TranslateMessage( &msg ); 
      DispatchMessage ( &msg ); 
    } 
  } //end of infinite loop

Click Debug → Start Without Debugging Ctrl F5.
Experiments: (Recover the change after any experiment.)

Hundred Triangles

Add the following declarations just below the line int WINAPI WinMain( ... ).
The head of int WINAPI WinMain( ... ) should look like this:

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int iCmdShow)
{ const int nTriangles = 100;
  float dx[nTriangles];
  float dy[nTriangles];
  float dz[nTriangles];
  float ax[nTriangles];
  float ay[nTriangles];
  float az[nTriangles];
  srand( (unsigned)time(NULL) ); //initialize random number generator
  for ( int i=0; i < nTriangles; i++ )
  { dx[i] = -0.5f + (float)rand() / RAND_MAX; //something between -0.5 and +0.5
    dy[i] = -0.5f + (float)rand() / RAND_MAX; //something between -0.5 and +0.5
    dz[i] = -0.5f + (float)rand() / RAND_MAX; //something between -0.5 and +0.5
    ax[i] = 90.0f * (float)rand() / RAND_MAX; //something between  0.0 and 90.0
    ay[i] = 90.0f * (float)rand() / RAND_MAX; //something between  0.0 and 90.0
    az[i] = 90.0f * (float)rand() / RAND_MAX; //something between  0.0 and 90.0
  }
  WNDCLASS wc;
  .
  .

Change the while ( TRUE ) //infinite loop as follows:

  while ( TRUE ) //infinite loop
  { glClearColor( 0.0f, 0.0f, 0.0f, 0.0f );
    glClear( GL_COLOR_BUFFER_BIT );
    for ( int i=0; i < nTriangles; i++ )
    { glLoadIdentity(); //erase all former transforms
      glScalef( 0.7f, 0.7f, 0.7f );
      glRotatef( ax[i]+=0.1f, 1.0f, 0.0f, 0.0f ); //around x-axis
      glRotatef( ay[i]+=0.1f, 0.0f, 1.0f, 0.0f ); //around y-axis
      glRotatef( az[i]+=0.1f, 0.0f, 0.0f, 1.0f ); //around z-axis
      glTranslatef( dx[i], dy[i], dz[i] );         //shifts
      glDrawArrays( GL_TRIANGLES, 0, 3 );          //draw it
    }
    SwapBuffers( hDC ); //show all
    MSG msg;            //listen to what happens outside the loop
    if ( PeekMessage( &msg, NULL, 0, 0, PM_REMOVE ) )
    { if ( msg.message == WM_QUIT ) return 0; //stop infinite loop
      TranslateMessage( &msg ); 
      DispatchMessage ( &msg ); 
    } 
  } //end of infinite loop

Click Debug → Start Without Debugging Ctrl F5. Hundred small triangles will dance as flying paper sheets do.

Experiments: (Recover the change after any experiment.)

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