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View Full Version : Masking woes....again!



Al Grant
05-20-2006, 08:08 PM
Hi guys,

Last time I masked a textured quad with a black and white mask using glBlendFunc(Gl_DST_COLOR,GL_ZERO).

Now I want to do the same thing, but instead of the bottom quad being a textured quad, the bottom quad is just a quad whose color I have set with glcolor3f(0.0f,1.0f,0.0f) etc.

Now for some reason I am gettng the dreaded black screen again!!

Could some please take a look at my code?

Thanks
-Al


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

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

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
bool masking=TRUE; // Masking On/Off
bool mp; // M Pressed?
bool sp; // Space Pressed?
bool scene; // Which Scene To Draw

GLuint texture[2]; // Storage For Our Two Textures
GLuint loop; // Generic Loop Variable

GLfloat roll; // Rolling Texture

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

AUX_RGBImageRec *LoadBMP(char *Filename) // Loads A Bitmap Image
{
FILE *File=NULL; // File Handle
if (!Filename) // Make Sure A Filename Was Given
{
return NULL; // If Not Return NULL
}
File=fopen(Filename,"r"); // Check To See If The File Exists
if (File) // Does The File Exist?
{
fclose(File); // Close The Handle
return auxDIBImageLoad(Filename); // Load The Bitmap And Return A Pointer
}
return NULL; // If Load Failed Return NULL
}

int LoadGLTextures() // Load Bitmaps And Convert To Textures
{
int Status=FALSE; // Status Indicator
AUX_RGBImageRec *TextureImage[2]; // Create Storage Space For The Texture Data
memset(TextureImage,0,sizeof(void *)*2); // Set The Pointer To NULL

if ((TextureImage[0]=LoadBMP("mask.bmp")) &amp;&amp; // Logo Texture
(TextureImage[1]=LoadBMP("Untitled-1.bmp"))) // First Mask

{
Status=TRUE; // Set The Status To TRUE
glGenTextures(2, &amp;texture[0]); // Create Five Textures

for (loop=0; loop<2; loop++) // Loop Through All 5 Textures
{
glBindTexture(GL_TEXTURE_2D, texture[loop]);
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTE R,GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTE R,GL_LINEAR);
glTexImage2D(GL_TEXTURE_2D, 0, 3, TextureImage[loop]->sizeX, TextureImage[loop]->sizeY,
0, GL_RGB, GL_UNSIGNED_BYTE, TextureImage[loop]->data);
}
}
for (loop=0; loop<2; loop++) // Loop Through All 5 Textures
{
if (TextureImage[loop]) // If Texture Exists
{
if (TextureImage[loop]->data) // If Texture Image Exists
{
free(TextureImage[loop]->data); // Free The Texture Image Memory
}
free(TextureImage[loop]); // Free The Image Structure
}
}
return Status; // Return The Status
}



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
{
if (!LoadGLTextures()) // Jump To Texture Loading Routine
{
return FALSE; // If Texture Didn't Load Return FALSE
}
glShadeModel(GL_SMOOTH); // Enable Smooth Shading
glClearColor(0.4f, 0.4f, 0.4f, 0.0f); // Black Background
glClearDepth(1.0f); // Depth Buffer Setup
glEnable(GL_DEPTH_TEST);
glEnable(GL_TEXTURE_2D); // Enable 2D Texture Mapping
// 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
glTranslatef(0.0f,0.0f,-5.0f);



glBegin(GL_QUADS); // Draw A Quad
glColor3f(0.0f, 0.6f, 0.796f);
glVertex3f(-1.5f, 18.0f, 0.0f); // Top Left
glVertex3f( 1.5f, 18.0f, 0.0f); // Top Right
glVertex3f( 1.5f, 0.0f, 0.0f); // Bottom Right
glVertex3f(-1.5f, 0.0f, 0.0f); // Bottom Left

glColor3f(0.694f, 0.4f, 0.0f);
glVertex3f(-1.5f, -18.0f, 0.0f); // Top Left
glVertex3f( 1.5f, -18.0f, 0.0f); // Top Right
glVertex3f( 1.5f, 0.0f, 0.0f); // Bottom Right
glVertex3f(-1.5f, 0.0f, 0.0f); // Bottom Left
glEnd();

glBegin(GL_LINES);
glColor3f(1.0f, 1.0f, 1.0f);

glVertex3f(-1.5f, 0.0f, 0.0f);
glVertex3f(1.5f, 0.0f, 0.0f);

glVertex3f(-0.6f, 1.0f, 0.0f);
glVertex3f(0.6f, 1.0f, 0.0f);
glEnd();


glEnable(GL_BLEND);
glDisable(GL_DEPTH_TEST);
glBlendFunc(GL_DST_COLOR,GL_ZERO);

glBindTexture(GL_TEXTURE_2D, texture[0]);
glBegin(GL_QUADS); // Start Drawing A Textured Quad
glTexCoord2f(0.0f, 1.0f); glVertex3f(-2.0f, 2.0f, 0.0f); // Bottom Left
glTexCoord2f(1.0f, 1.0f); glVertex3f(2.0f, 2.0f, 0.0f); // Bottom Right
glTexCoord2f(1.0f, 0.0f); glVertex3f(2.0f, -2.0f, 0.0f); // Top Right
glTexCoord2f(0.0f, 0.0f); glVertex3f(-2.0f, -2.0f, 0.0f); // Top Left
glEnd();

glDisable(GL_BLEND);

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 &amp;&amp; !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 &amp;&amp; !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(&amp;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(&amp;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_PELSWID TH|DM_PELSHEIGHT;

// Try To Set Selected Mode And Get Results. NOTE: CDS_FULLSCREEN Gets Rid Of Start Bar.
if (ChangeDisplaySettings(&amp;dmScreenSettings,CDS_FULLS CREEN)!=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(&amp;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,&amp;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,&amp;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

// 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 OpenGL Framework",640,480,16,fullscreen))
{
return 0; // Quit If Window Was Not Created
}

while(!done) // Loop That Runs While done=FALSE
{
if (PeekMessage(&amp;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(&amp;msg); // Translate The Message
DispatchMessage(&amp;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)
}
}

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 OpenGL Framework",640,480,16,fullscreen))
{
return 0; // Quit If Window Was Not Created
}
}
}
}

// Shutdown
KillGLWindow(); // Kill The Window
return (msg.wParam); // Exit The Program
}

sqrt[-1]
05-21-2006, 01:16 AM
The problem is that you still have texturing enabled, so it will use the last texture bound (the masked texture) and the last texture coordinates (black pixel)

Might I suggest you come familar with the tool GLIntercept and use the XML frame grab(CTRL-SHIFT-F) to show you what each render call is doing?

http://glintercept.nutty.org/

Example:
http://home.swiftdsl.com.au/~radlegend/GLIntercept/Demo04/gliInterceptLog.xml

In this case you can see that you had a texture being used in the render call when rendering the color background.


Here is the new code:

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
glTranslatef(0.0f,0.0f,-5.0f);

//**** Disable texturing
glDisable(GL_TEXTURE_2D);

glBegin(GL_QUADS); // Draw A Quad
glColor3f(0.0f, 0.6f, 0.796f);
glVertex3f(-1.5f, 18.0f, 0.0f); // Top Left
glVertex3f( 1.5f, 18.0f, 0.0f); // Top Right
glVertex3f( 1.5f, 0.0f, 0.0f); // Bottom Right
glVertex3f(-1.5f, 0.0f, 0.0f); // Bottom Left

glColor3f(0.694f, 0.4f, 0.0f);
glVertex3f(-1.5f, -18.0f, 0.0f); // Top Left
glVertex3f( 1.5f, -18.0f, 0.0f); // Top Right
glVertex3f( 1.5f, 0.0f, 0.0f); // Bottom Right
glVertex3f(-1.5f, 0.0f, 0.0f); // Bottom Left
glEnd();

glBegin(GL_LINES);
glColor3f(1.0f, 1.0f, 1.0f);

glVertex3f(-1.5f, 0.0f, 0.0f);
glVertex3f(1.5f, 0.0f, 0.0f);

glVertex3f(-0.6f, 1.0f, 0.0f);
glVertex3f(0.6f, 1.0f, 0.0f);
glEnd();

//**** Enable texturing
glEnable(GL_TEXTURE_2D);

glEnable(GL_BLEND);
glDisable(GL_DEPTH_TEST);
glBlendFunc(GL_DST_COLOR,GL_ZERO);

glBindTexture(GL_TEXTURE_2D, texture[0]);
glBegin(GL_QUADS); // Start Drawing A Textured Quad
glTexCoord2f(0.0f, 1.0f); glVertex3f(-2.0f, 2.0f, 0.0f); // Bottom Left
glTexCoord2f(1.0f, 1.0f); glVertex3f(2.0f, 2.0f, 0.0f); // Bottom Right
glTexCoord2f(1.0f, 0.0f); glVertex3f(2.0f, -2.0f, 0.0f); // Top Right
glTexCoord2f(0.0f, 0.0f); glVertex3f(-2.0f, -2.0f, 0.0f); // Top Left
glEnd();

glDisable(GL_BLEND);

return TRUE; // Everything Went OK
}

Al Grant
05-21-2006, 04:13 AM
Yep -That did the trick.