Finally, if the 4 key on the number pad is pressed, our particle will pull more to the left. These keys give us some really cool results. For example, you can make a stream of particles shooting straight up in the air. By adding some gravity pulling downwards you can turn the stream of particles into a fountain of water!
// If Number Pad 4 And X Gravity Is Greater Than –1.5 Increase Pull Left
if (keys[VK_NUMPAD4] && (particle[loop].xg>-1.5f)) particle[loop].xg-=0.01f;
I added this bit of code just for fun. My brother thought the explosion was a cool effect :) By pressing the tab key all the particles will be reset back to the center of the screen. The moving speed of the particles will once again be multiplied by 10, creating a big explosion of particles. After the particles fade out, your original effect will again reappear.
if (keys[VK_TAB]) // Tab Key Causes A Burst
{
particle[loop].x=0.0f; // Center On X Axis
particle[loop].y=0.0f; // Center On Y Axis
particle[loop].z=0.0f; // Center On Z Axis
particle[loop].xi=float((rand()%50)-26.0f)*10.0f; // Random Speed On X Axis
particle[loop].yi=float((rand()%50)-25.0f)*10.0f; // Random Speed On Y Axis
particle[loop].zi=float((rand()%50)-25.0f)*10.0f; // Random Speed On Z Axis
}
}
}
return TRUE; // Everything Went OK
}
The code in KillGLWindow(), CreateGLWindow() and WndProc() hasn't changed, so we'll skip down to WinMain(). I'll rewrite the entire section of code to make it easier to follow through the 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
}
// Create Our OpenGL Window
if (!CreateGLWindow("NeHe's Particle Tutorial", 640, 480, 16, fullscreen)) {
return 0; // Quit If Window Was Not Created
}
This is our first change to WinMain(). I've added some code to check if the user decide to run in fullscreen mode or windowed mode. If they decide to use fullscreen mode, I change the variable slowdown to 1.0f instead of 2.0f. You can leave this bit code out if you want. I added the code to speed up fullscreen mode on my 3dfx (runs ALOT slower than windowed mode for some reason).
if (fullscreen) // Are We In Fullscreen Mode ( ADD )
{
slowdown=1.0f; // Speed Up The Particles (3dfx Issue) ( ADD )
}
while(!done) // Loop That Runs Until done=TRUE
{
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
{
if ((active && !DrawGLScene()) || keys[VK_ESCAPE]) // Updating View Only If Active
{
done=TRUE; // ESC or DrawGLScene Signalled A Quit
} else // Not Time To Quit, Update Screen
{
SwapBuffers(hDC); // Swap Buffers (Double Buffering)
I was a little sloppy with the next bit of code. Usually I don't include everything on one line, but it makes the code look a little cleaner :)
The line below checks to see if the + key on the number pad is being pressed. If it is and slowdown is greater than 1.0f we decrease slowdown by 0.01f. This causes the particles to move faster. Remember in the code above when I talked about slowdown and how it affects the speed at which the particles travel.
if (keys[VK_ADD] && (slowdown>1.0f)) slowdown-=0.01f; // Speed Up Particles
This line checks to see if the – key on the number pad is being pressed. If it is and slowdown is less than 4.0f we increase the value of slowdown. This causes our particles to move slower. I put a limit of 4.0f because I wouldn't want them to move much slower. You can change the minimum and maximum speeds to whatever you want :)
if (keys[VK_SUBTRACT] && (slowdown<4.0f)) slowdown+=0.01f; // Slow Down Particles
The line below check to see if Page Up is being pressed. If it is, the variable zoom is increased. This causes the particles to move closer to us.
if (keys[VK_PRIOR]) zoom+=0.1f; // Zoom In
This line has the opposite effect. By pressing Page Down, zoom is decreased and the scene moves futher into the screen. This allows us to see more of the screen, but it makes the particles smaller.
if (keys[VK_NEXT]) zoom-=0.1f; // Zoom Out
The next section of code checks to see if the return key has been pressed. If it has and it's not being 'held' down, we'll let the computer know it's being pressed by setting rp to true. Then we'll toggle rainbow mode. If rainbow was true, it will become false. If it was false, it will become true. The last line checks to see if the return key was released. If it was, rp is set to false, telling the computer that the key is no longer being held down.
if (keys[VK_RETURN] && !rp) // Return Key Pressed
{
rp=true; // Set Flag Telling Us It's Pressed
rainbow=!rainbow; // Toggle Rainbow Mode On / Off
}
if (!keys[VK_RETURN]) rp=false; // If Return Is Released Clear Flag
The code below is a little confusing. The first line checks to see if the spacebar is being pressed and not held down. It also check to see if rainbow mode is on, and if so, it checks to see if the variable delay is greater than 25. delay is a counter I use to create the rainbow effect. If you were to change the color ever frame, the particles would all be a different color. By creating a delay, a group of particles will become one color, before the color is changed to something else.
If the spacebar was pressed or rainbow is on and delay is greater than 25, the color will be changed!
if ((keys[' '] && !sp) || (rainbow && (delay>25))) // Space Or Rainbow Mode
{
The line below was added so that rainbow mode would be turned off if the spacebar was pressed. If we didn't turn off rainbow mode, the colors would continue cycling until the return key was pressed again. It makes sense that if the person is hitting space instead of return that they want to go through the colors themselves.
if (keys[' ']) rainbow=false; // If Spacebar Is Pressed Disable Rainbow Mode