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How do you fade out a scene?

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I was making a little opengl demo. I was wondering how to "fade out" a scene. How do you do that?

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The simplest way is to simply blend a black quad over the scene and vary the alpha. Alternatively you could change the colour each frame, so glColor3f(r, g, b) would become glColor3f(r * fade, g * fade, b * fade) where fade goes from 1 to 0.

Enigma

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Just wondering...
What if it is necessary not to fade out the scene, but vice versa. That it it becomes brighter, brighter, brighter... will, in this case, blending a white quad with increasing alpha do the job? (never tried this, so one solution is to try , but maybe anyone has better experience?
)

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Alpha doesn''t work for me...
BTW, I''m not using lights yet... just trying to get the scene to fade...

But the r*fade, g*fade, b*fade worked! Thanx!

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@BrennendeKomet: Yeah, it will work. Just use glColor4f( r, g, b, alpha ). rgb is the color to fade to and change alpha slowly form 0 to 1. Blending mode should be set to (src_alpha, one_minus_src_alpha)

@Big Cheez: you need the right blend mode for alpha to work.

[edited by - _DarkWIng_ on February 8, 2004 6:54:30 AM]

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Ah. So it''s blending that you see whenever you see something semitransparent in OpenGL. So I''ll read the blending tutorial. Thanx!

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Great. Just great. Blending doesn''t work!


#include <windows.h> // Header File For Windows

#include <math.h> // Header File For Windows Math Library

#include <stdio.h> // Header File For Standard Input/Output

#include <stdarg.h> // Header File For Variable Argument Routines

#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 <time.h>

HDC hDC=NULL; // Private GDI Device Context

HGLRC hRC=NULL; // Permanent Rendering Context

HWND hWnd=NULL; // Holds Our Window Handle

HINSTANCE hInstance; // Holds The Instance Of The Application


GLfloat cnt1; // 1st Counter Used For Coloring

GLfloat cnt2; // 2nd Counter Used For Coloring


bool keys[256]; // Array Used For The Keyboard Routine

bool active=TRUE; // Window Active Flag Set To TRUE By Default

bool fullscreen=TRUE; // Fullscreen Flag Set To Fullscreen Mode By Default


float rot8=0.0;
int scene=1;
int cyclesElapsed=0;
float fade=1.0;

int i=0; //for for loops


float junk=0; //whatever we want


LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM); // Declaration For WndProc


GLvoid 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

{
glColor4f(1.0f,1.0f,1.0f,0.5f);
glBlendFunc(GL_SRC_ALPHA,GL_ONE);
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

{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); // Clear Screen And Depth Buffer

glLoadIdentity(); // Reset The Current Modelview Matrix

cyclesElapsed+=1;
glDisable(GL_BLEND);
glEnable(GL_DEPTH_TEST);
switch(scene){
case 1:
glEnable(GL_BLEND);
glDisable(GL_DEPTH_TEST);
glTranslatef(0,0,-6);
glRotatef(rot8,1,1,1);
rot8+=0.5;
glBegin(GL_QUADS);
glColor4f(0,0,1,0.5); //blue

glVertex3f( 1.0f, 1.0f,-1.0f); // Top Right Of The Quad (Top)

glVertex3f(-1.0f, 1.0f,-1.0f); // Top Left Of The Quad (Top)

glVertex3f(-1.0f, 1.0f, 1.0f); // Bottom Left Of The Quad (Top)

glVertex3f( 1.0f, 1.0f, 1.0f); // Bottom Right Of The Quad (Top)


glVertex3f( 1.0f,-1.0f, 1.0f); // Top Right Of The Quad (Bottom)

glVertex3f(-1.0f,-1.0f, 1.0f); // Top Left Of The Quad (Bottom)

glVertex3f(-1.0f,-1.0f,-1.0f); // Bottom Left Of The Quad (Bottom)

glVertex3f( 1.0f,-1.0f,-1.0f); // Bottom Right Of The Quad (Bottom)


glVertex3f( 1.0f, 1.0f, 1.0f); // Top Right Of The Quad (Front)

glVertex3f(-1.0f, 1.0f, 1.0f); // Top Left Of The Quad (Front)

glVertex3f(-1.0f,-1.0f, 1.0f); // Bottom Left Of The Quad (Front)

glVertex3f( 1.0f,-1.0f, 1.0f); // Bottom Right Of The Quad (Front)


glVertex3f( 1.0f,-1.0f,-1.0f); // Bottom Left Of The Quad (Back)

glVertex3f(-1.0f,-1.0f,-1.0f); // Bottom Right Of The Quad (Back)

glVertex3f(-1.0f, 1.0f,-1.0f); // Top Right Of The Quad (Back)

glVertex3f( 1.0f, 1.0f,-1.0f); // Top Left Of The Quad (Back)


glVertex3f(-1.0f, 1.0f, 1.0f); // Top Right Of The Quad (Left)

glVertex3f(-1.0f, 1.0f,-1.0f); // Top Left Of The Quad (Left)

glVertex3f(-1.0f,-1.0f,-1.0f); // Bottom Left Of The Quad (Left)

glVertex3f(-1.0f,-1.0f, 1.0f); // Bottom Right Of The Quad (Left)


glVertex3f( 1.0f, 1.0f,-1.0f); // Top Right Of The Quad (Right)

glVertex3f( 1.0f, 1.0f, 1.0f); // Top Left Of The Quad (Right)

glVertex3f( 1.0f,-1.0f, 1.0f); // Bottom Left Of The Quad (Right)

glVertex3f( 1.0f,-1.0f,-1.0f); // Bottom Right Of The Quad (Right)

glEnd();
if(cyclesElapsed>=2500){
cyclesElapsed=0;
scene+=1;
}
break;

case 2:
glEnable(GL_BLEND);
glDisable(GL_DEPTH_TEST);
glTranslatef(0,0,-6);
glRotatef(rot8,1,1,1);
rot8+=0.5;
glBegin(GL_QUADS);
glColor3f(1.0f*float(cos(cnt1)),1.0f*float(sin(cnt2)),1.0f-0.5f*float(cos(cnt1+cnt2)));//rainbow

glVertex3f( 1.0f, 1.0f,-1.0f); // Top Right Of The Quad (Top)

glVertex3f(-1.0f, 1.0f,-1.0f); // Top Left Of The Quad (Top)

glVertex3f(-1.0f, 1.0f, 1.0f); // Bottom Left Of The Quad (Top)

glVertex3f( 1.0f, 1.0f, 1.0f); // Bottom Right Of The Quad (Top)


glVertex3f( 1.0f,-1.0f, 1.0f); // Top Right Of The Quad (Bottom)

glVertex3f(-1.0f,-1.0f, 1.0f); // Top Left Of The Quad (Bottom)

glVertex3f(-1.0f,-1.0f,-1.0f); // Bottom Left Of The Quad (Bottom)

glVertex3f( 1.0f,-1.0f,-1.0f); // Bottom Right Of The Quad (Bottom)


glVertex3f( 1.0f, 1.0f, 1.0f); // Top Right Of The Quad (Front)

glVertex3f(-1.0f, 1.0f, 1.0f); // Top Left Of The Quad (Front)

glVertex3f(-1.0f,-1.0f, 1.0f); // Bottom Left Of The Quad (Front)

glVertex3f( 1.0f,-1.0f, 1.0f); // Bottom Right Of The Quad (Front)


glVertex3f( 1.0f,-1.0f,-1.0f); // Bottom Left Of The Quad (Back)

glVertex3f(-1.0f,-1.0f,-1.0f); // Bottom Right Of The Quad (Back)

glVertex3f(-1.0f, 1.0f,-1.0f); // Top Right Of The Quad (Back)

glVertex3f( 1.0f, 1.0f,-1.0f); // Top Left Of The Quad (Back)


glVertex3f(-1.0f, 1.0f, 1.0f); // Top Right Of The Quad (Left)

glVertex3f(-1.0f, 1.0f,-1.0f); // Top Left Of The Quad (Left)

glVertex3f(-1.0f,-1.0f,-1.0f); // Bottom Left Of The Quad (Left)

glVertex3f(-1.0f,-1.0f, 1.0f); // Bottom Right Of The Quad (Left)


glVertex3f( 1.0f, 1.0f,-1.0f); // Top Right Of The Quad (Right)

glVertex3f( 1.0f, 1.0f, 1.0f); // Top Left Of The Quad (Right)

glVertex3f( 1.0f,-1.0f, 1.0f); // Bottom Left Of The Quad (Right)

glVertex3f( 1.0f,-1.0f,-1.0f); // Bottom Right Of The Quad (Right)

glEnd();

cnt1+=0.007f;
cnt2+=0.005f;

if(cyclesElapsed>=2500){
cyclesElapsed=0;
scene+=1;
}
break;

case 3:
glEnable(GL_BLEND);
glDisable(GL_DEPTH_TEST);
if(fade>0){
glTranslatef(0,0,-6);
glRotatef(rot8,1,1,1);
rot8+=0.5;
glBegin(GL_QUADS);
glColor3f(0,0,fade); //blue

glVertex3f( 1.0f, 1.0f,-1.0f); // Top Right Of The Quad (Top)

glVertex3f(-1.0f, 1.0f,-1.0f); // Top Left Of The Quad (Top)

glVertex3f(-1.0f, 1.0f, 1.0f); // Bottom Left Of The Quad (Top)

glVertex3f( 1.0f, 1.0f, 1.0f); // Bottom Right Of The Quad (Top)


glVertex3f( 1.0f,-1.0f, 1.0f); // Top Right Of The Quad (Bottom)

glVertex3f(-1.0f,-1.0f, 1.0f); // Top Left Of The Quad (Bottom)

glVertex3f(-1.0f,-1.0f,-1.0f); // Bottom Left Of The Quad (Bottom)

glVertex3f( 1.0f,-1.0f,-1.0f); // Bottom Right Of The Quad (Bottom)


glVertex3f( 1.0f, 1.0f, 1.0f); // Top Right Of The Quad (Front)

glVertex3f(-1.0f, 1.0f, 1.0f); // Top Left Of The Quad (Front)

glVertex3f(-1.0f,-1.0f, 1.0f); // Bottom Left Of The Quad (Front)

glVertex3f( 1.0f,-1.0f, 1.0f); // Bottom Right Of The Quad (Front)


glVertex3f( 1.0f,-1.0f,-1.0f); // Bottom Left Of The Quad (Back)

glVertex3f(-1.0f,-1.0f,-1.0f); // Bottom Right Of The Quad (Back)

glVertex3f(-1.0f, 1.0f,-1.0f); // Top Right Of The Quad (Back)

glVertex3f( 1.0f, 1.0f,-1.0f); // Top Left Of The Quad (Back)


glVertex3f(-1.0f, 1.0f, 1.0f); // Top Right Of The Quad (Left)

glVertex3f(-1.0f, 1.0f,-1.0f); // Top Left Of The Quad (Left)

glVertex3f(-1.0f,-1.0f,-1.0f); // Bottom Left Of The Quad (Left)

glVertex3f(-1.0f,-1.0f, 1.0f); // Bottom Right Of The Quad (Left)


glVertex3f( 1.0f, 1.0f,-1.0f); // Top Right Of The Quad (Right)

glVertex3f( 1.0f, 1.0f, 1.0f); // Top Left Of The Quad (Right)

glVertex3f( 1.0f,-1.0f, 1.0f); // Bottom Left Of The Quad (Right)

glVertex3f( 1.0f,-1.0f,-1.0f); // Bottom Right Of The Quad (Right)

glEnd();

fade-=0.004;
}

if(cyclesElapsed>=300){
cyclesElapsed=0;
scene+=1;
}
break;

default:
break;
}
return TRUE; // Everything Went OK

}

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

}
}

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_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


// Create Our OpenGL Window

if (!CreateGLWindow("Demo",1024,768,32,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) // Program Active?

{
if (keys[VK_ESCAPE]) // Was ESC Pressed?

{
done=TRUE; // ESC Signalled A Quit

}
else // Not Time To Quit, Update Screen

{
DrawGLScene(); // Draw The Scene

SwapBuffers(hDC); // Swap Buffers (Double Buffering)

}
}
}
}

// Shutdown

KillGLWindow(); // Kill The Window

return (msg.wParam); // Exit The Program

}

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To enable blending, you must set the alpha value which you can only set when using glColor4x(r,g,b,a); where a is the alpha value (used for blending, mostly as transparancy).

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Post a screenshot and i'll see what's wrong.

EDIT: also, draw the blended quads after al the others and depth sorted, else some visible data will not be drawn (as they will be behind the drawn blended quad (so actually visible), but are depth tested away as they are behind it). Another thing you can do when drawing the blended quads it turning the depth mask (drawing to the depth buffer) off this way: glDepthMask(false). This way the quads drawn after the blended quads will not be tested away, however this might (probably will) cause the blended quads to overdrawn. Just play around a bit and you'll figure out what suits you best.

[edited by - Tree Penguin on February 8, 2004 8:01:43 AM]

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Do you have webspace ? If so, place it there and place this in your post:

img src="the image url with http://, else it will be searched at the gamedev page"

and that between a < and a >

If you don't have any webspace, email the image to me, and i'll put it online if i don't know the problem.

[edited by - Tree Penguin on February 8, 2004 8:04:38 AM]

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post the new code to see what you are doing now...

You should never let your fears become the boundaries of your dreams.

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2 Big Cheez:

You know, there is nothing strange that it doesn''t work
The code you posted is not far from being awfull... well, even if we forget about good programming style, the code is completely un readible!
Let me give you some hints, of course it is not the best way to write this program, however while cleaning up your code you will find the error yourself. That i promise

First of all, remove those tons of glVertex3d() calls! You print the same lines thousant times! It''d be much better if you moved the minimal essential glVertex3d() operations in one function, then just:
0) setup attributes (blending, depth testing...)
1) prepare matrix (glTranslate, glRotate...)
2) call drawing function.

After that: i couldn''t find exactly where you specify the value of "scene" variable (oh, yes, for further convinence give the variables meaningfull names, for example, if you see iScene - you understand that it is the integer value, and specifies the scene, fOffsetCoordX - means floating-point value of X offset coordinate...) But, outside of switch structure you disable blending, while in all of brenches in switch structure you enable it! What for?

After that, just check for sure the number (if there any defaults) and order of parameters you pass for each function...

... well this is only a beginning, but i''m sure that if you start with that, you will understand yourself the source of the error

And, please, consider this post just like a friendly advice , but not something <...> in any sense
i hope many of those contributed to this thread will agree with me...

P.S. are you sure you really need: glBlendFunc(GL_SRC_ALPHA,GL_ONE); ?

C++ RULEZ!!!

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BrennendeKomet: Can I point you at Hungarian wartHogs? I feel that nobody should use hungarian notation without being aware of its shortcomings. If you are already aware of these issues and have still chosen to use hungarian notation then I have absolutely no problem with that.

Enigma

EDIT: typo

[edited by - Enigma on February 8, 2004 10:01:07 AM]

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Stile is a topic for itself but Komet is right, a function or two for the sake of a nice program structure wouldn''t hurt...

But well, back to fading. Here''s some code i used for a fading intro screen:

//////////////////////////////////////////////////////////////

CSGL_Texture logo; // Just a Texture class
logo.SGL_LoadTexture("Textures\\logo.bmp");

float time = timeGetTime()/10;
float alpha = 0;
GLuint Llogo;

Llogo = glGenLists(1);
glNewList(Llogo,GL_COMPILE);
logo.SGL_BindTexture();
glBegin(GL_QUADS);
glTexCoord2f(0.0f, 0.0f); glVertex3f(-1.4f, -1.0f, -2.5f);
glTexCoord2f(1.0f, 0.0f); glVertex3f( 1.4f, -1.0f, -2.5f);
glTexCoord2f(1.0f, 1.0f); glVertex3f( 1.4f, 1.0f, -2.5f);
glTexCoord2f(0.0f, 1.0f); glVertex3f(-1.4f, 1.0f, -2.5f);
glEnd();
glEndList();

glBlendFunc(GL_SRC_ALPHA,GL_ONE);
glEnable(GL_BLEND);

while((timeGetTime() / 10) - time < 650)
{
SGL_ResetScene(); // calls glClear() and glLoadIdentity()
glColor4f(1,1,1,sin(alpha));
glCallList(Llogo);
alpha += 0.01f;
SGL_SwapBuffers(); // calls SwapBuffers()
}

/////////////////////////////////////////////////////////////

using sin() and a constant time isn''t the best way because it just works fine with a specific frame-rate, but the sample shows a basic way to fade in and out a screen.
Hope it helps a bit.

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@Enigma:
Thanks you for the link! Actually, i have not yet seen that story (by the way it is an interesting reading!).
Well, you are right, maybe i had to take more neutral position... to say the truth, i had no idea that there was any strict distictions in notations, even that they have names

Now, i understand, that i myself use neither one nor other named notation, rather some combination of them, which, i think, is common and unique to a programmer/group of programmers worling together.

Finally, i''d like to quote one thing from the story you kindly presented:

quote:

"I believe source code is a form of communication," the Guru pressed on. "The question is, who is that communication aimed at? The compiler? No. Source code is a medium of communication from one programmer to another. It is an expression of intent, of what is desired to happen. We must strive to keep that communication as simple and clear as possible. In order to do that, variable names should reflect the roles that those variables play."



C++ RULEZ!!!

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indeed, varibles should express ''role'' but NOT type infomation, its role might not change, and if it does it should be renamed, but its type can change without its roll being changed, which is why you can end up with iVar being a float :o

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quote:
Original post by pest1010100
By the way... how to make this code-window?


use [ source ] and [ /source ] tags, without spaces of course...
...and one tip: if you want to find out how something in someone''s post is done, just ckick "edit" on his post, and look for necessary tags in the quoted post!

Good Luck!

C++ RULEZ!!!

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