Jeff Molofee - NeHe's OpenGL Tutorials

glRotatef(xrot, 1.0f, 0.0f, 0.0f); // Rotate On The X Axis

glRotatef(yrot, 0.0f, 1.0f, 0.0f); // Rotate On The Y Axis

DrawObject(); // Draw The Ball

The following code rotates the ball on the x and y axis. By increasing xrot by xrotspeed we rotate the ball on the x-axis. By increasing yrot by yrotspeed we spin the ball on the y-axis. If xrotspeed is a very high value in the positive or negative direction the ball will spin quicker than if xrotspeed was a low value, closer to 0.0f. Same goes for yrotspeed. The higher the value, the faster the ball spins on the y-axis.

Before we return TRUE, we do a glFlush(). This tells OpenGL to render everything left in the GL pipeline before continuing, and can help prevent flickering on slower video cards.

xrot += xrotspeed; // Update X Rotation Angle By xrotspeed

yrot += yrotspeed; // Update Y Rotation Angle By yrotspeed

glFlush(); // Flush The GL Pipeline

return TRUE; // Everything Went OK

}

The following code will watch for key presses. The first 4 lines check to see if you are pressing one of the 4 arrow keys. If you are, the ball is spun right, left, down or up.

The next 2 lines check to see if you are pressing the 'A' or 'Z' keys. Pressing 'A' will zoom you in closer to the ball and pressing 'Z' will zoom you away from the ball.

Pressing 'PAGE UP' will increase the value of height moving the ball up, and pressing 'PAGE DOWN' will decrease the value of height moving the ball down (closer to the floor).

void ProcessKeyboard() // Process Keyboard Results

{

if (keys[VK_RIGHT]) yrotspeed += 0.08f; // Right Arrow Pressed (Increase yrotspeed)

if (keys[VK_LEFT]) yrotspeed –= 0.08f; // Left Arrow Pressed (Decrease yrotspeed)

if (keys[VK_DOWN]) xrotspeed += 0.08f; // Down Arrow Pressed (Increase xrotspeed)

if (keys[VK_UP]) xrotspeed –= 0.08f; // Up Arrow Pressed (Decrease xrotspeed)

if (keys['A']) zoom +=0.05f; // 'A' Key Pressed … Zoom In

if (keys['Z']) zoom –=0.05f; // 'Z' Key Pressed … Zoom Out

if (keys[VK_PRIOR]) height +=0.03f; // Page Up Key Pressed Move Ball Up

if (keys[VK_NEXT]) height –=0.03f; // Page Down Key Pressed Move Ball Down

}

The KillGLWindow() code hasn't changed, so I'll skip over it.

GLvoid KillGLWindow(GLvoid) // Properly Kill The Window

You can skim through the following code. Even though only one line of code has changed in CreateGLWindow(), I have included all of the code so it's easier to follow through the tutorial.

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

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 | WS_CLIPSIBLINGS | WS_CLIPCHILDREN; // Windows Style

ShowCursor(FALSE); // Hide Mouse Pointer

} else

{

dwExStyle=WS_EX_APPWINDOW | WS_EX_WINDOWEDGE; // Window Extended Style

dwStyle=WS_OVERLAPPEDWINDOW | WS_CLIPSIBLINGS | WS_CLIPCHILDREN;// Windows Style

}

// Create The Window

if (!(hWnd=CreateWindowEx( dwExStyle, // Extended Style For The Window

"OpenGL", // Class Name

title, // Window Title

dwStyle, // Window Style

0, 0, // Window Position

width, height, // Selected Width And 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