double spriteX = 0f;    //spriteXdouble spriteY = 0f;    //spriteYdouble mouseX =  100f;    //mouseXdouble mouseY =  100f;  //mouseYdouble rotate = (Math.Atan2(mouseY-spriteY,mouseX-spriteX) / Math.PI) * 180;rotate = Math.Abs(rotate);if (mouseY > spriteY) rotate = -rotate;

GLfloat rotate = abs((GLfloat)atan2((GLfloat)my-oy,(GLfloat)mx-ox))/PI*180.0f; if (my > oy) rotate = -rotate; glRotatef(rotate,0.0f,0.0f,1.0f);

#include <windows.h>		// Header File For Windows#include <gl\gl.h>			// Header File For The OpenGL32 Library#include <gl\glu.h>			// Header File For The GLu32 Library#include <gl\glaux.h>		// Header File For The Glaux Library#include <math.h>#define PI       3.14159265358979323846HDC			hDC=NULL;		// Private GDI Device ContextHGLRC		hRC=NULL;		// Permanent Rendering ContextHWND		hWnd=NULL;		// Holds Our Window HandleHINSTANCE	hInstance;		// Holds The Instance Of The Applicationbool	keys[256];			// Array Used For The Keyboard Routinebool	active=TRUE;		// Window Active Flag Set To TRUE By Defaultbool	fullscreen=TRUE;	// Fullscreen Flag Set To Fullscreen Mode By Defaultint mx=0;int my=0;GLfloat	rtri;				// Angle For The Triangle ( NEW )GLfloat	rquad;				// Angle For The Quad ( NEW )LRESULT	CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);	// Declaration For WndProcGLvoid ReSizeGLScene(GLsizei width, GLsizei height)		// Resize And Initialize The GL Window{	if (height==0)										// Prevent A Divide By Zero By	{		height=1;										// Making Height Equal One	}	glViewport(0,0,width,height);						// Reset The Current Viewport	glMatrixMode(GL_PROJECTION);						// Select The Projection Matrix	glLoadIdentity();									// Reset The Projection Matrix	// Calculate The Aspect Ratio Of The Window	gluPerspective(45.0f,(GLfloat)width/(GLfloat)height,0.1f,100.0f);	glMatrixMode(GL_MODELVIEW);							// Select The Modelview Matrix	glLoadIdentity();									// Reset The Modelview Matrix}int InitGL(GLvoid)										// All Setup For OpenGL Goes Here{	glShadeModel(GL_SMOOTH);							// Enable Smooth Shading	glClearColor(0.0f, 0.0f, 0.0f, 0.5f);				// Black Background	glClearDepth(1.0f);									// Depth Buffer Setup	glEnable(GL_DEPTH_TEST);							// Enables Depth Testing	glDepthFunc(GL_LEQUAL);								// The Type Of Depth Testing To Do	glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST);	// Really Nice Perspective Calculations	return TRUE;										// Initialization Went OK}int DrawGLScene(GLvoid)									// Here's Where We Do All The Drawing{	int ox=640/2; //SPRITE POINT X (center of screen for this example)	int oy=480/2; //SPRITE POINT Y (center of screen for this example)	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);	// Clear Screen And Depth Buffer	glLoadIdentity();									// Reset The Current Modelview Matrix	glTranslatef(0.0f,0.0f,-10.0f);	      				// Move Left 1.5 Units And Into The Screen 6.0	glRotatef(-90.0f,0.0f,0.0f,1.0f);					//Point the triangle to 0deg	//BY_PICKLED/////////////////////////////////////////////////////////////////	GLfloat rotate = abs((GLfloat)atan2((GLfloat)my-oy,(GLfloat)mx-ox))/PI*180.0f; //ROTATE TO MOUSE	if (my > oy)		rotate = -rotate; 	glRotatef(rotate,0.0f,0.0f,1.0f); 	//BY_PICKLED/////////////////////////////////////////////////////////////////	glBegin(GL_TRIANGLES);								// Start Drawing A Triangle		glColor3f(1.0f,0.0f,0.0f);						// Set Top Point Of Triangle To Red		glVertex3f( 0.0f, 1.0f, 0.0f);					// First Point Of The Triangle		glColor3f(0.0f,1.0f,0.0f);						// Set Left Point Of Triangle To Green		glVertex3f(-1.0f,-1.0f, 0.0f);					// Second Point Of The Triangle		glColor3f(0.0f,1.0f,0.0f);						// Set Right Point Of Triangle To Blue		glVertex3f( 1.0f,-1.0f, 0.0f);					// Third Point Of The Triangle	glEnd();											// Done Drawing The Triangle		rtri+=0.2f;											// Increase The Rotation Variable For The Triangle ( NEW )		return TRUE;										// Keep Going}GLvoid KillGLWindow(GLvoid)								// Properly Kill The Window{	if (fullscreen)										// Are We In Fullscreen Mode?	{		ChangeDisplaySettings(NULL,0);					// If So Switch Back To The Desktop		ShowCursor(TRUE);								// Show Mouse Pointer	}	if (hRC)											// Do We Have A Rendering Context?	{		if (!wglMakeCurrent(NULL,NULL))					// Are We Able To Release The DC And RC Contexts?		{			MessageBox(NULL,"Release Of DC And RC Failed.","SHUTDOWN ERROR",MB_OK | MB_ICONINFORMATION);		}		if (!wglDeleteContext(hRC))						// Are We Able To Delete The RC?		{			MessageBox(NULL,"Release Rendering Context Failed.","SHUTDOWN ERROR",MB_OK | MB_ICONINFORMATION);		}		hRC=NULL;										// Set RC To NULL	}	if (hDC && !ReleaseDC(hWnd,hDC))					// Are We Able To Release The DC	{		MessageBox(NULL,"Release Device Context Failed.","SHUTDOWN ERROR",MB_OK | MB_ICONINFORMATION);		hDC=NULL;										// Set DC To NULL	}	if (hWnd && !DestroyWindow(hWnd))					// Are We Able To Destroy The Window?	{		MessageBox(NULL,"Could Not Release hWnd.","SHUTDOWN ERROR",MB_OK | MB_ICONINFORMATION);		hWnd=NULL;										// Set hWnd To NULL	}	if (!UnregisterClass("OpenGL",hInstance))			// Are We Able To Unregister Class	{		MessageBox(NULL,"Could Not Unregister Class.","SHUTDOWN ERROR",MB_OK | MB_ICONINFORMATION);		hInstance=NULL;									// Set hInstance To NULL	}}/*	This Code Creates Our OpenGL Window.  Parameters Are:					* *	title			- Title To Appear At The Top Of The Window				* *	width			- Width Of The GL Window Or Fullscreen Mode				* *	height			- Height Of The GL Window Or Fullscreen Mode			* *	bits			- Number Of Bits To Use For Color (8/16/24/32)			* *	fullscreenflag	- Use Fullscreen Mode (TRUE) Or Windowed Mode (FALSE)	*/ BOOL CreateGLWindow(char* title, int width, int height, int bits, bool fullscreenflag){	GLuint		PixelFormat;			// Holds The Results After Searching For A Match	WNDCLASS	wc;						// Windows Class Structure	DWORD		dwExStyle;				// Window Extended Style	DWORD		dwStyle;				// Window Style	RECT		WindowRect;				// Grabs Rectangle Upper Left / Lower Right Values	WindowRect.left=(long)0;			// Set Left Value To 0	WindowRect.right=(long)width;		// Set Right Value To Requested Width	WindowRect.top=(long)0;				// Set Top Value To 0	WindowRect.bottom=(long)height;		// Set Bottom Value To Requested Height	fullscreen=fullscreenflag;			// Set The Global Fullscreen Flag	hInstance			= GetModuleHandle(NULL);				// Grab An Instance For Our Window	wc.style			= CS_HREDRAW | CS_VREDRAW | CS_OWNDC;	// Redraw On Size, And Own DC For Window.	wc.lpfnWndProc		= (WNDPROC) WndProc;					// WndProc Handles Messages	wc.cbClsExtra		= 0;									// No Extra Window Data	wc.cbWndExtra		= 0;									// No Extra Window Data	wc.hInstance		= hInstance;							// Set The Instance	wc.hIcon			= LoadIcon(NULL, IDI_WINLOGO);			// Load The Default Icon	wc.hCursor			= LoadCursor(NULL, IDC_ARROW);			// Load The Arrow Pointer	wc.hbrBackground	= NULL;									// No Background Required For GL	wc.lpszMenuName		= NULL;									// We Don't Want A Menu	wc.lpszClassName	= "OpenGL";								// Set The Class Name	if (!RegisterClass(&wc))									// Attempt To Register The Window Class	{		MessageBox(NULL,"Failed To Register The Window Class.","ERROR",MB_OK|MB_ICONEXCLAMATION);		return FALSE;											// Return FALSE	}		if (fullscreen)												// Attempt Fullscreen Mode?	{		DEVMODE dmScreenSettings;								// Device Mode		memset(&dmScreenSettings,0,sizeof(dmScreenSettings));	// Makes Sure Memory's Cleared		dmScreenSettings.dmSize=sizeof(dmScreenSettings);		// Size Of The Devmode Structure		dmScreenSettings.dmPelsWidth	= width;				// Selected Screen Width		dmScreenSettings.dmPelsHeight	= height;				// Selected Screen Height		dmScreenSettings.dmBitsPerPel	= bits;					// Selected Bits Per Pixel		dmScreenSettings.dmFields=DM_BITSPERPEL|DM_PELSWIDTH|DM_PELSHEIGHT;		// Try To Set Selected Mode And Get Results.  NOTE: CDS_FULLSCREEN Gets Rid Of Start Bar.		if (ChangeDisplaySettings(&dmScreenSettings,CDS_FULLSCREEN)!=DISP_CHANGE_SUCCESSFUL)		{			// If The Mode Fails, Offer Two Options.  Quit Or Use Windowed Mode.			if (MessageBox(NULL,"The Requested Fullscreen Mode Is Not Supported By\nYour Video Card. Use Windowed Mode Instead?","NeHe GL",MB_YESNO|MB_ICONEXCLAMATION)==IDYES)			{				fullscreen=FALSE;		// Windowed Mode Selected.  Fullscreen = FALSE			}			else			{				// Pop Up A Message Box Letting User Know The Program Is Closing.				MessageBox(NULL,"Program Will Now Close.","ERROR",MB_OK|MB_ICONSTOP);				return FALSE;									// Return FALSE			}		}	}	if (fullscreen)												// Are We Still In Fullscreen Mode?	{		dwExStyle=WS_EX_APPWINDOW;								// Window Extended Style		dwStyle=WS_POPUP;										// Windows Style		//ShowCursor(FALSE);										// Hide Mouse Pointer	}	else	{		dwExStyle=WS_EX_APPWINDOW | WS_EX_WINDOWEDGE;			// Window Extended Style		dwStyle=WS_OVERLAPPEDWINDOW;							// Windows Style	}	AdjustWindowRectEx(&WindowRect, dwStyle, FALSE, dwExStyle);		// Adjust Window To True Requested Size	// Create The Window	if (!(hWnd=CreateWindowEx(	dwExStyle,							// Extended Style For The Window								"OpenGL",							// Class Name								title,								// Window Title								dwStyle |							// Defined Window Style								WS_CLIPSIBLINGS |					// Required Window Style								WS_CLIPCHILDREN,					// Required Window Style								0, 0,								// Window Position								WindowRect.right-WindowRect.left,	// Calculate Window Width								WindowRect.bottom-WindowRect.top,	// Calculate Window Height								NULL,								// No Parent Window								NULL,								// No Menu								hInstance,							// Instance								NULL)))								// Dont Pass Anything To WM_CREATE	{		KillGLWindow();								// Reset The Display		MessageBox(NULL,"Window Creation Error.","ERROR",MB_OK|MB_ICONEXCLAMATION);		return FALSE;								// Return FALSE	}	static	PIXELFORMATDESCRIPTOR pfd=				// pfd Tells Windows How We Want Things To Be	{		sizeof(PIXELFORMATDESCRIPTOR),				// Size Of This Pixel Format Descriptor		1,											// Version Number		PFD_DRAW_TO_WINDOW |						// Format Must Support Window		PFD_SUPPORT_OPENGL |						// Format Must Support OpenGL		PFD_DOUBLEBUFFER,							// Must Support Double Buffering		PFD_TYPE_RGBA,								// Request An RGBA Format		bits,										// Select Our Color Depth		0, 0, 0, 0, 0, 0,							// Color Bits Ignored		0,											// No Alpha Buffer		0,											// Shift Bit Ignored		0,											// No Accumulation Buffer		0, 0, 0, 0,									// Accumulation Bits Ignored		16,											// 16Bit Z-Buffer (Depth Buffer)  		0,											// No Stencil Buffer		0,											// No Auxiliary Buffer		PFD_MAIN_PLANE,								// Main Drawing Layer		0,											// Reserved		0, 0, 0										// Layer Masks Ignored	};		if (!(hDC=GetDC(hWnd)))							// Did We Get A Device Context?	{		KillGLWindow();								// Reset The Display		MessageBox(NULL,"Can't Create A GL Device Context.","ERROR",MB_OK|MB_ICONEXCLAMATION);		return FALSE;								// Return FALSE	}	if (!(PixelFormat=ChoosePixelFormat(hDC,&pfd)))	// Did Windows Find A Matching Pixel Format?	{		KillGLWindow();								// Reset The Display		MessageBox(NULL,"Can't Find A Suitable PixelFormat.","ERROR",MB_OK|MB_ICONEXCLAMATION);		return FALSE;								// Return FALSE	}	if(!SetPixelFormat(hDC,PixelFormat,&pfd))		// Are We Able To Set The Pixel Format?	{		KillGLWindow();								// Reset The Display		MessageBox(NULL,"Can't Set The PixelFormat.","ERROR",MB_OK|MB_ICONEXCLAMATION);		return FALSE;								// Return FALSE	}	if (!(hRC=wglCreateContext(hDC)))				// Are We Able To Get A Rendering Context?	{		KillGLWindow();								// Reset The Display		MessageBox(NULL,"Can't Create A GL Rendering Context.","ERROR",MB_OK|MB_ICONEXCLAMATION);		return FALSE;								// Return FALSE	}	if(!wglMakeCurrent(hDC,hRC))					// Try To Activate The Rendering Context	{		KillGLWindow();								// Reset The Display		MessageBox(NULL,"Can't Activate The GL Rendering Context.","ERROR",MB_OK|MB_ICONEXCLAMATION);		return FALSE;								// Return FALSE	}	ShowWindow(hWnd,SW_SHOW);						// Show The Window	SetForegroundWindow(hWnd);						// Slightly Higher Priority	SetFocus(hWnd);									// Sets Keyboard Focus To The Window	ReSizeGLScene(width, height);					// Set Up Our Perspective GL Screen	if (!InitGL())									// Initialize Our Newly Created GL Window	{		KillGLWindow();								// Reset The Display		MessageBox(NULL,"Initialization Failed.","ERROR",MB_OK|MB_ICONEXCLAMATION);		return FALSE;								// Return FALSE	}	return TRUE;									// Success}LRESULT CALLBACK WndProc(	HWND	hWnd,			// Handle For This Window							UINT	uMsg,			// Message For This Window							WPARAM	wParam,			// Additional Message Information							LPARAM	lParam)			// Additional Message Information{	switch (uMsg)									// Check For Windows Messages	{		case WM_ACTIVATE:							// Watch For Window Activate Message		{			if (!HIWORD(wParam))					// Check Minimization State			{				active=TRUE;						// Program Is Active			}			else			{				active=FALSE;						// Program Is No Longer Active			}			return 0;								// Return To The Message Loop		}				case WM_MOUSEMOVE:		{			mx = LOWORD(lParam);			my = HIWORD(lParam);		}		case WM_SYSCOMMAND:							// Intercept System Commands		{			switch (wParam)							// Check System Calls			{				case SC_SCREENSAVE:					// Screensaver Trying To Start?				case SC_MONITORPOWER:				// Monitor Trying To Enter Powersave?				return 0;							// Prevent From Happening			}			break;									// Exit		}		case WM_CLOSE:								// Did We Receive A Close Message?		{			PostQuitMessage(0);						// Send A Quit Message			return 0;								// Jump Back		}		case WM_KEYDOWN:							// Is A Key Being Held Down?		{			keys[wParam] = TRUE;					// If So, Mark It As TRUE			return 0;								// Jump Back		}		case WM_KEYUP:								// Has A Key Been Released?		{			keys[wParam] = FALSE;					// If So, Mark It As FALSE			return 0;								// Jump Back		}		case WM_SIZE:								// Resize The OpenGL Window		{			ReSizeGLScene(LOWORD(lParam),HIWORD(lParam));  // LoWord=Width, HiWord=Height			return 0;								// Jump Back		}	}	// Pass All Unhandled Messages To DefWindowProc	return DefWindowProc(hWnd,uMsg,wParam,lParam);}int WINAPI WinMain(	HINSTANCE	hInstance,			// Instance					HINSTANCE	hPrevInstance,		// Previous Instance					LPSTR		lpCmdLine,			// Command Line Parameters					int			nCmdShow)			// Window Show State{	MSG		msg;									// Windows Message Structure	BOOL	done=FALSE;								// Bool Variable To Exit Loop	// Ask The User Which Screen Mode They Prefer	//if (MessageBox(NULL,"Would You Like To Run In Fullscreen Mode?", "Start FullScreen?",MB_YESNO|MB_ICONQUESTION)==IDNO)	//{		fullscreen=FALSE;							// Windowed Mode	//}	// Create Our OpenGL Window	if (!CreateGLWindow("NeHe's Rotation Tutorial",640,480,16,fullscreen))	{		return 0;									// Quit If Window Was Not Created	}	while(!done)									// Loop That Runs While done=FALSE	{		if (PeekMessage(&msg,NULL,0,0,PM_REMOVE))	// Is There A Message Waiting?		{			if (msg.message==WM_QUIT)				// Have We Received A Quit Message?			{				done=TRUE;							// If So done=TRUE			}			else									// If Not, Deal With Window Messages			{				TranslateMessage(&msg);				// Translate The Message				DispatchMessage(&msg);				// Dispatch The Message			}		}		else										// If There Are No Messages		{			// Draw The Scene.  Watch For ESC Key And Quit Messages From DrawGLScene()			if ((active && !DrawGLScene()) || keys[VK_ESCAPE])	// Active?  Was There A Quit Received?			{				done=TRUE;							// ESC or DrawGLScene Signalled A Quit			}			else									// Not Time To Quit, Update Screen			{				SwapBuffers(hDC);					// Swap Buffers (Double Buffering)			}			if (keys[VK_F1])						// Is F1 Being Pressed?			{				keys[VK_F1]=FALSE;					// If So Make Key FALSE				KillGLWindow();						// Kill Our Current Window				fullscreen=!fullscreen;				// Toggle Fullscreen / Windowed Mode				// Recreate Our OpenGL Window				if (!CreateGLWindow("NeHe's Rotation Tutorial",640,480,16,fullscreen))				{					return 0;						// Quit If Window Was Not Created				}			}		}	}	// Shutdown	KillGLWindow();									// Kill The Window	return (msg.wParam);							// Exit The Program}