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Hello Everyone, After days of tinkering with gluUnproject I still can''t get it to work properly. Does anyone have a Windows console application that uses gluUnproject, and draws an object according to the mouse cursor? I know this is quite specific, but I thought that asking can''t hurt.. Will greatly appreciate any and all help!!! --Udi

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go on NeHes site and read article 13 (if you don''t know where the articles are, look in the left-hand column). This has also been discussed about 50+ times on these forums.

------------------------------------------------------
Regret Nothing - Learn Everything

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Hi All,

Thanks for the pointers. I actually was aware of the other postings regarding this subject, and also the article. The reason I posted my question is that no matter what I do, I''m getting something wrong: my object seems to follow my mouse cursor, but not accurately. I''m guessing I''m doing something really stupid, and other than that it should work properly.
Can anyone take a look? It really is a very simple program - very little of it is actually used for the drawing and the glUnproject routines, I just left it all in so it would be easy to run... Btw, it''s based on one of NeHe''s FANTASTIC tutorials as you''d quickly see.. I even left most of the comments inside.

Many many many thanks!!!!!!
Udi

#include <windows.h>
#include <gl\gl.h>
#include <gl\glu.h>
#include <gl\glaux.h>
#include <iomanip>
#include <fstream>


HGLRC hRC=NULL;
HDC hDC=NULL;
HWND hWnd=NULL; // Holds Our Window Handle
HINSTANCE hInstance;

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

int omx, omy, mx, my; // mouse parameters
float depth_parameter = 0;
float horizontal_parameter = 0.0f;
float vertical_parameter = 0.0f;
float rotation_parameter = 0.0f;
bool leftMouseBut = false;
bool rightMouseBut = false;
bool mouseMove = false;
GLdouble ox=0.0,oy=0.0,oz=0.0;
GLfloat nmx, nmy, nmz;

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
{

glShadeModel(GL_SMOOTH); // Enables Smooth Shading

glClearColor(0.0f, 0.0f, 0.0f, 0.0f); // Black Background

glClearDepth(1.0f); // Depth Buffer Setup
glEnable (GL_BLEND);

//BlendFunc (GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
glBlendFunc (GL_SRC_ALPHA, GL_ONE);

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 The Screen And The Depth Buffer


glLoadIdentity();

glTranslated(ox, oy, oz);
glColor4f(1.0f,1.0f,1.0f, 1.0f);

glBegin(GL_QUADS);
glVertex3f(-1.0f, 1.0f, 0.0f);
glVertex3f( 1.0f, 1.0f, 0.0f);
glVertex3f( 1.0f,-1.0f, 0.0f);
glVertex3f(-1.0f,-1.0f, 0.0f);
glEnd();


return TRUE;
}


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 Move, 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; // Exit And 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 Run In A Window.
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; // Select Windowed Mode (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; // Exit And Return FALSE
}
}
}

if (fullscreen) // Are We Still In Fullscreen Mode?
{

dwExnostyle=WS_EX_APPWINDOW; // Window Extended Style
dwnostyle=WS_POPUP; // Windows Style
ShowCursor(FALSE); // Hide Mouse Pointer
}
else
{

dwExnostyle=WS_EX_APPWINDOW | WS_EX_WINDOWEDGE; // Window Extended Style
dwnostyle=WS_OVERLAPPEDWINDOW; // Windows Style
}

AdjustWindowRectEx(&WindowRect, dwStyle, FALSE, dwExStyle); // Adjust Window To True Requested Size

if (!(hWnd=CreateWindowEx( dwExStyle, // Extended Style For The Window
"OpenGL", // Class Name
title, // Window Title
WS_CLIPSIBLINGS | // Required Window Style
WS_CLIPCHILDREN | // Required Window Style
dwStyle, // Selected Window Style
0, 0, // Window Position
WindowRect.right-WindowRect.left, // Calculate Adjusted Window Width
WindowRect.bottom-WindowRect.top, // Calculate Adjusted Window Height
NULL, // No Parent Window
NULL, // No Menu
hInstance, // Instance
NULL))) // Don''t 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
}

case WM_LBUTTONDOWN:
{
SetCapture(hWnd);
depth_parameter=depth_parameter-0.1;

mx = LOWORD(lParam);
my = HIWORD(lParam);
leftMouseBut = true;

return 0;
}
case WM_RBUTTONDOWN:
{
SetCapture(hWnd);
mx = LOWORD(lParam);
my = HIWORD(lParam);
depth_parameter=depth_parameter+0.1;
rightMouseBut = true;
return 0;
}
case WM_LBUTTONUP:
{
leftMouseBut = false;
ReleaseCapture();
return 0;
}
case WM_RBUTTONUP:
{
rightMouseBut = false;
ReleaseCapture();
return 0;
}

case WM_MOUSEMOVE:
{
omx = mx;
omy = my;
mx = LOWORD(lParam);
my = HIWORD(lParam);
if (mx<0) mx=0;
if (mx>65000) mx=0;
if (my<0) my=0;
if (my>65000) my=0;

int dx = mx - omx;
int dy = my - omy;

GLint viewport[4];
GLdouble modelview[16],projection[16];
GLdouble wx,wy,wz;

glGetIntegerv(GL_VIEWPORT,viewport);

nmx = mx;
nmy = viewport[3]-my;

glReadPixels(nmx, nmy, 1, 1, GL_DEPTH_COMPONENT, GL_FLOAT, &nmz);

glGetDoublev(GL_MODELVIEW_MATRIX,modelview);
glGetDoublev(GL_PROJECTION_MATRIX,projection);

gluUnProject( nmx, nmy, nmz, modelview, projection, viewport, &wx, &wy, &wz);
ox = wx;
oy = wy;
oz = wz;

if ((leftMouseBut) && (!rightMouseBut))
{
depth_parameter=depth_parameter+5*(dx / 100.0f);
}
else if ((!leftMouseBut) && (rightMouseBut))
{
horizontal_parameter=horizontal_parameter+(dx / 100.0f);

vertical_parameter=vertical_parameter-dy / 100.0f;
}
else if ((leftMouseBut) && (rightMouseBut))
{
rotation_parameter=rotation_parameter+5*(dx / 100.0f);
}

return 0;
}
}

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))
if (!CreateGLWindow("First attempt",800,800,16,fullscreen))
{
return 0; // Quit If Window Was Not Created
}

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
{

// 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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Hmm, confused me a little at first.

The problem is where you get the modelview matrix. First time your matrix is the identity matrix. Next time the matrix is not identity because you''ve translated in order to draw your square! In order to correct this you should either:
A) glLoadIdentity() before you glGetDoublev(GL_MODELVIEW_MATRIX, ...)
or
B) glPushMatrix() and glPopMatrix() around your quad drawing.

B is the better solution as your camera does not need to be at the origin/pointing down Z.

I''m not sure what you''re doing at the moment with all your omx, nmx, dx e.t.c. They can all be eliminated as shown below.

Here''s a bit of code:

int DrawGLScene(GLvoid) // Here''s Where We Do All The Drawing
{

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


glLoadIdentity();
glPushMatrix();
glTranslated(ox, oy, oz);
glColor4f(1.0f,1.0f,1.0f, 1.0f);

glBegin(GL_QUADS);
glVertex3f(-1.0f, 1.0f, 0.0f);
glVertex3f( 1.0f, 1.0f, 0.0f);
glVertex3f( 1.0f,-1.0f, 0.0f);
glVertex3f(-1.0f,-1.0f, 0.0f);
glEnd();
glPopMatrix();

return TRUE;
}

and in WndProc:

case WM_MOUSEMOVE:
{
mx = LOWORD(lParam);
my = HIWORD(lParam);
GLint viewport[4];
GLdouble modelview[16];
GLdouble projection[16];
glGetIntegerv(GL_VIEWPORT, viewport);
glGetDoublev(GL_MODELVIEW_MATRIX, modelview);
glGetDoublev(GL_PROJECTION_MATRIX, projection);
gluUnProject(mx, viewport[3] - (my + 1), 1.0, modelview, projection, viewport, &ox, &oy, &oz);
return 0;
}


Enigma

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Thanks so much Enigma! What you''re saying makes sense. I think some aspects of OpenGL I really do need to work on..
There''s one really strange thing I noticed: the code DOESN''T WORK (meaning, the white square isn''t centered on my cursor) UNTIL I maximize & minimize the window... and then it works.
Isn''t that strange!? can it be some kind of a driver bug ?!?!

Udi

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Yeah, I forgot to mention that. I don''t know what OS you''re using but I ran it under windows XP. The problem is that the code calls ReSizeGLScene with the requested width and height (in this case 800 by 800) but XP clips the window to the display resolution (in my case 800 by 768), so the square is offset a bit (in my case by 32 pixels) until ReSizeGLScene is called again with the correct window width and height. I thought about trying to fix this, but havn''t got round to it yet. Try removing the ReSizeGLScene call from CreateGLWindow and see if that works.

Enigma

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