C++: Forest Fire

Bjarne-stroustrup
 

Implement the Drossel and Schwabl definition of the forest-fire model.

It is basically a 2D cellular automaton where each cell can be in three distinct states (empty, tree and burning) and evolves according to the following rules (as given by Wikipedia)

  1. A burning cell turns into an empty cell
  2. A tree will burn if at least one neighbor is burning
  3. A tree ignites with probability f even if no neighbor is burning
  4. An empty space fills with a tree with probability p

Neighborhood is the Moore neighborhood; boundary conditions are so that on the boundary the cells are always empty (“fixed” boundary condition).

At the beginning, populate the lattice with empty and tree cells according to a specific probability (e.g. a cell has the probability 0.5 to be a tree). Then, let the system evolve.

Task’s requirements do not include graphical display or the ability to change parameters (probabilities p and f) through a graphical or command line interface.

ForestFireCpp.png

#include <windows.h>
#include <string>

//--------------------------------------------------------------------------------------------------
using namespace std;

//--------------------------------------------------------------------------------------------------
enum states { NONE, TREE, FIRE };
const int MAX_SIDE = 500;

//--------------------------------------------------------------------------------------------------
class myBitmap
{
public:
	myBitmap() : pen( NULL ) {}
	~myBitmap()
	{
		DeleteObject( pen );
		DeleteDC( hdc );
		DeleteObject( bmp );
	}

	bool create( int w, int h )
	{
		BITMAPINFO	bi;
		ZeroMemory( &bi, sizeof( bi ) );

		bi.bmiHeader.biSize	   = sizeof( bi.bmiHeader );
		bi.bmiHeader.biBitCount	   = sizeof( DWORD ) * 8;
		bi.bmiHeader.biCompression = BI_RGB;
		bi.bmiHeader.biPlanes	   = 1;
		bi.bmiHeader.biWidth	   =  w;
		bi.bmiHeader.biHeight	   = -h;

		HDC dc = GetDC( GetConsoleWindow() );
		bmp = CreateDIBSection( dc, &bi, DIB_RGB_COLORS, &pBits, NULL, 0 );
		if( !bmp ) return false;

		hdc = CreateCompatibleDC( dc );
		SelectObject( hdc, bmp );
		ReleaseDC( GetConsoleWindow(), dc ); 

		width = w; height = h;

		return true;
	}

	void clear()
	{
		ZeroMemory( pBits, width * height * sizeof( DWORD ) );
	}

	void setPenColor( DWORD clr )
	{
		if( pen ) DeleteObject( pen );
		pen = CreatePen( PS_SOLID, 1, clr );
		SelectObject( hdc, pen );
	}

	void saveBitmap( string path )
	{
		BITMAPFILEHEADER fileheader;
		BITMAPINFO	 infoheader;
		BITMAP		 bitmap;
		DWORD		 wb;

		GetObject( bmp, sizeof( bitmap ), &bitmap );

		DWORD* dwpBits = new DWORD[bitmap.bmWidth * bitmap.bmHeight];
		ZeroMemory( dwpBits, bitmap.bmWidth * bitmap.bmHeight * sizeof( DWORD ) );
		ZeroMemory( &infoheader, sizeof( BITMAPINFO ) );
		ZeroMemory( &fileheader, sizeof( BITMAPFILEHEADER ) );

		infoheader.bmiHeader.biBitCount = sizeof( DWORD ) * 8;
		infoheader.bmiHeader.biCompression = BI_RGB;
		infoheader.bmiHeader.biPlanes = 1;
		infoheader.bmiHeader.biSize = sizeof( infoheader.bmiHeader );
		infoheader.bmiHeader.biHeight = bitmap.bmHeight;
		infoheader.bmiHeader.biWidth = bitmap.bmWidth;
		infoheader.bmiHeader.biSizeImage = bitmap.bmWidth * bitmap.bmHeight * sizeof( DWORD );

		fileheader.bfType    = 0x4D42;
		fileheader.bfOffBits = sizeof( infoheader.bmiHeader ) + sizeof( BITMAPFILEHEADER );
		fileheader.bfSize    = fileheader.bfOffBits + infoheader.bmiHeader.biSizeImage;

		GetDIBits( hdc, bmp, 0, height, ( LPVOID )dwpBits, &infoheader, DIB_RGB_COLORS );

		HANDLE file = CreateFile( path.c_str(), GENERIC_WRITE, 0, NULL, CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL );
		WriteFile( file, &fileheader, sizeof( BITMAPFILEHEADER ), &wb, NULL );
		WriteFile( file, &infoheader.bmiHeader, sizeof( infoheader.bmiHeader ), &wb, NULL );
		WriteFile( file, dwpBits, bitmap.bmWidth * bitmap.bmHeight * 4, &wb, NULL );
		CloseHandle( file );

		delete [] dwpBits;
	}

	HDC getDC() const     { return hdc; }
	int getWidth() const  { return width; }
	int getHeight() const { return height; }

private:
	HBITMAP bmp;
	HDC	    hdc;
	HPEN    pen;
	void	*pBits;
	int	    width, height;
};
//--------------------------------------------------------------------------------------------------
class forest
{
public:
	forest()
	{
		_bmp.create( MAX_SIDE, MAX_SIDE ); 
		initForest( 0.05f, 0.005f );
	}

	void initForest( float p, float f )
	{
		_p = p; _f = f;
		seedForest();
	}

	void mainLoop()
	{
		display();
		simulate();
	}

	void setHWND( HWND hwnd ) { _hwnd = hwnd; }

private:
	float probRand() { return ( float )rand() / 32768.0f; }

	void display()
	{
		HDC bdc = _bmp.getDC();
		DWORD clr;

		for( int y = 0; y < MAX_SIDE; y++ )
		{
			for( int x = 0; x < MAX_SIDE; x++ )
			{
				switch( _forest[x][y] )
				{
				case FIRE: clr = 255; break;
				case TREE: clr = RGB( 0, 255, 0 ); break;
				default: clr = 0;
				}

				SetPixel( bdc, x, y, clr );
			}
		}

		HDC dc = GetDC( _hwnd );
		BitBlt( dc, 0, 0, MAX_SIDE, MAX_SIDE, _bmp.getDC(), 0, 0, SRCCOPY );
		ReleaseDC( _hwnd, dc );
	}

	void seedForest()
	{
		ZeroMemory( _forestT, sizeof( _forestT ) );
		ZeroMemory( _forest, sizeof( _forest ) );
		for( int y = 0; y < MAX_SIDE; y++ )
		for( int x = 0; x < MAX_SIDE; x++ )
		if( probRand() < _p ) _forest[x][y] = TREE;
	}

	bool getNeighbors( int x, int y )
	{
		int a, b;
		for( int yy = -1; yy < 2; yy++ )
		for( int xx = -1; xx < 2; xx++ )
		{
			if( !xx && !yy ) continue;
			a = x + xx; b = y + yy;
			if( a < MAX_SIDE && b < MAX_SIDE && a > -1 && b > -1 )
			if( _forest[a][b] == FIRE ) return true;
		}

		return false;
	}

	void simulate()
	{
		for( int y = 0; y < MAX_SIDE; y++ )
		{
			for( int x = 0; x < MAX_SIDE; x++ )
			{
				switch( _forest[x][y] )
				{
				case FIRE: _forestT[x][y] = NONE; break;
				case NONE: if( probRand() < _p ) _forestT[x][y] = TREE; break;
				case TREE: if( getNeighbors( x, y ) || probRand() < _f ) _forestT[x][y] = FIRE;
				}
			}
		}

		for( int y = 0; y < MAX_SIDE; y++ )
		for( int x = 0; x < MAX_SIDE; x++ )
		_forest[x][y] = _forestT[x][y];
	}

	myBitmap _bmp;
	HWND     _hwnd;
	BYTE     _forest[MAX_SIDE][MAX_SIDE], _forestT[MAX_SIDE][MAX_SIDE];
	float    _p, _f;
};
//--------------------------------------------------------------------------------------------------
class wnd
{
public:
	int wnd::Run( HINSTANCE hInst )
	{
		_hInst = hInst;
		_hwnd = InitAll();

		_ff.setHWND( _hwnd );
		_ff.initForest( 0.02f, 0.001f );

		ShowWindow( _hwnd, SW_SHOW );
		UpdateWindow( _hwnd );

		MSG msg;
		ZeroMemory( &msg, sizeof( msg ) );
		while( msg.message != WM_QUIT )
		{
			if( PeekMessage( &msg, NULL, 0, 0, PM_REMOVE ) != 0 )
			{
				TranslateMessage( &msg );
				DispatchMessage( &msg );
			}
			else
			{
				_ff.mainLoop();
			}
		}
		return UnregisterClass( "_FOREST_FIRE_", _hInst );
	}
private:
	static int WINAPI wnd::WndProc( HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam )
	{
		switch( msg )
		{
		case WM_DESTROY: PostQuitMessage( 0 ); break;
		default:
			return DefWindowProc( hWnd, msg, wParam, lParam );
		}
		return 0;
	}

	HWND InitAll()
	{
		WNDCLASSEX wcex;
		ZeroMemory( &wcex, sizeof( wcex ) );
		wcex.cbSize	       = sizeof( WNDCLASSEX );
		wcex.style	       = CS_HREDRAW | CS_VREDRAW;
		wcex.lpfnWndProc   = ( WNDPROC )WndProc;
		wcex.hInstance     = _hInst;
		wcex.hCursor       = LoadCursor( NULL, IDC_ARROW );
		wcex.hbrBackground = ( HBRUSH )( COLOR_WINDOW + 1 );
		wcex.lpszClassName = "_FOREST_FIRE_";

		RegisterClassEx( &wcex );

		return CreateWindow( "_FOREST_FIRE_", ".: Forest Fire -- PJorente :.", WS_SYSMENU, CW_USEDEFAULT, 0, MAX_SIDE, MAX_SIDE, NULL, NULL, _hInst, NULL );
	}

	HINSTANCE _hInst;
	HWND      _hwnd;
	forest    _ff;
};
//--------------------------------------------------------------------------------------------------
int APIENTRY _tWinMain( HINSTANCE hInstance, HINSTANCE hPrevInstance, LPTSTR lpCmdLine, int nCmdShow )
{
	srand( GetTickCount() );
	wnd myWnd;
	return myWnd.Run( hInstance );
}
//--------------------------------------------------------------------------------------------------

SOURCE

Content is available under GNU Free Documentation License 1.2.

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