Jeff Molofee - NeHe's OpenGL Tutorials

{

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

}

KillFont(); // Kill The Font We Built

}

The CreateGLWindow() and WndProc() code hasn't changed so search until you find the following section of code.

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

}

This section of code hasn't changed that much. I changed the window title to read "NeHe's Line Tutorial", and I added the ResetObjects() command. This sets the player to the top left point of the grid, and gives the enemies random starting locations. The enemies will always start off at least 5 tiles away from you. TimerInit() initializes the timer so it's set up properly.

if (!CreateGLWindow("NeHe's Line Tutorial", 640, 480, 16, fullscreen)) // Create Our OpenGL Window

{

return 0; // Quit If Window Was Not Created

}

ResetObjects(); // Set Player / Enemy Starting Positions

TimerInit(); // Initialize The Timer

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

{

Now to make the timing code work. Notice before we draw our scene we grab the time, and store it in a floating point variable called start. We then draw the scene and swap buffers.

Immediately after we swap the buffers we create a delay. We do this by checking to see if the current value of the timer (TimerGetTime( )) is less than our starting value plus the game stepping speed times 2. If the current timer value is less than the value we want, we endlessly loop until the current timer value is equal to or greater than the value we want. This slows down REALLY fast systems.

Because we use the stepping speed (set by the value of adjust) the program will always run the same speed. For example, if our stepping speed was 1 we would wait until the timer was greater than or equal to 2 (1*2). But if we increased the stepping speed to 2 (causing the player to move twice as many pixels at a time), the delay is increased to 4 (2*2). So even though we are moving twice as fast, the delay is twice as long, so the game still runs the same speed :)

One thing alot of people like to do is take the current time, and subtract the old time to find out how much time has passed. Then they move objects a certain distance based on the amount of time that has passed. Unfortunately I can't do that in this program because the fine movement has to be exact so that the player can line up with the lines on the grid. If the current fine x position was 59 and the computer decided the player needed to move two pixels, the player would never line up with the vertical line at position 60 on the grid.

float start=TimerGetTime(); // Grab Timer Value Before We Draw

// 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)

}

while(TimerGetTime() < start+float(steps[adjust]*2.0f)) {}// Waste Cycles On Fast Systems

The following code hasn't really changed. I changed the title of the window to read "NeHe's Line Tutorial".

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 Line Tutorial", 640, 480, 16, fullscreen)) {

return 0; // Quit If Window Was Not Created

}

}

This section of code checks to see if the A key is being pressed and not held. If 'A' is being pressed, ap becomes TRUE (telling our program that A is being held down), and anti is toggled from TRUE to FALSE or FALSE to TRUE. Remember that anti is checked in the drawing code to see if antialiasing is turned on or off.

If the 'A' key has been released (is FALSE) then ap is set to FALSE telling the program that the key is no longer being held down.

if (keys['A'] && !ap) // If 'A' Key Is Pressed And Not Held

{

ap=TRUE; // ap Becomes TRUE

anti=!anti; // Toggle Antialiasing

}

if (!keys['A']) // If 'A' Key Has Been Released

{

ap=FALSE; // ap Becomes FALSE

}

Now to move the enemies. I wanted to keep this section of code really simple. There is very little logic. Basically, the enemies check to see where you are and they move in that direction. Because I'm checking the actual x and y position of the players and no the fine values, the players seem to have a little more intelligence. They may see that you are way at the top of the screen. But by the time they're fine value actually gets to the top of the screen, you could already be in a different location. This causes them to sometimes move past you, before they realize you are no longer where they thought you were. May sound like they're really dumb, but because they sometimes move past you, you might find yourself being boxed in from all directions.