I am doing an excercise where I draw three boxes across three windows using GLUT. They draw individually, but in the same project, the three windows display correctly, but immediately close the program with code 1.
glutInitWindowPosition(x,y);
windowOne = glutCreateWindow("windowOne");
glClearColor(1.0, 1.0, 1.0, 0.0);
glMatrixMode(GL_PROJECTION);
glOrtho(-400, 400, -400, 400, -500, 500);
glutInitWindowPosition(x,y);
windowTwo = glutCreateWindow("windowTwo");
glClearColor(1.0, 1.0, 1.0, 0.0);
glMatrixMode(GL_PROJECTION);
glFrustum(-60, 60, -60, 60, 60, 200);
gluLookAt(0, 0, 120, 0, 0, 0, 0, 1, 0);
With each window in a separate file loaded in by itself, they each display exactly as they are meant to. I have a feeling I should be setting the window at some point between each init, but I don't know why. I do not have a draw function in at the moment, as I wanted to confirm this happens without the drawing code.
I should also note that I have to create separate windows, exactly as I have done, so other window drawing functions are useless.
I found the answer scouring through examples, so I'll post it just in case anyone else is having similar problems.
the draw function needs to be added after each window, in the style of
// window one
glutInitWindowPosition(50, 50);
WindowOne = glutCreateWindow("orthogonal projection");
glutDisplayFunc(drawWindowOne);
// window two
glutInitWindowPosition(650, 50);
WindowThree = glutCreateWindow("3D viewing system with glFrustum()");
glutDisplayFunc(drawWindowTwo);
I was using a draw function that shuffles through each window and generates its specific draw after using glutSetWindow. each draw takes place after each window is initialized, and multiple glutDisplayFunc() can be called after eachother.
I originally thought I was using glutDisplayFunc to set a pointer, so that when the display routine went through for the frame, it would only generate the last display function called, as opposed to all of them.
Never do OpenGL drawing operations in the same function in which you also create GLUT windows. It doesn't work. You need to register a display callback function for each window and do all drawing there. Calling glutMainLoop is mandatory if you want to see something sensible using GLUT.
Related
I have been learning about SDL 2D programming for a while and now I wanted to create a program using SDL and OpenGL combined. I set it up like this:
SDL_Init(SDL_INIT_VIDEO);
window = SDL_CreateWindow("SDL and OpenGL", SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, width, height, SDL_WINDOW_OPENGL);
context = SDL_GL_CreateContext(window);
The program is for now just a black window with a white line displayed using OpenGl. Here is the code for the rendering:
glClearColor(0, 0, 0, 0);
glClear(GL_COLOR_BUFFER_BIT);
glBegin(GL_LINES);
glVertex2d(1, 0);
glVertex2d(-1, 0);
glEnd();
SDL_GL_SwapWindow(window);
So the thing is, I would like to render textures additionally using pure SDL and a SDL_Renderer object, as I did before without OpenGL. I tried that out but it didn't work. Is it even possible to do that and how? What I did is creating a SDL_Renderer and then after drawing OpenGL stuff doing this:
SDL_Rect fillRect;
fillRect.w = 50;
fillRect.h = 50;
fillRect.x = 0;
fillRect.y = 0;
SDL_SetRenderDrawColor(renderer, 100, 200, 100, 0);
SDL_RenderFillRect(renderer, &fillRect);
SDL_RenderPresent(renderer);
But this does not work. The rectangle is not shown, although for some milliseconds it appears slightly. I feel like the OpenGL rendering is overwriting it.
SDL uses OpenGL (or in some cases Direct3D) and OpenGL has internal state which affects the GL calls in your program. The current version of SDL does not clearly indicate which states it changes or depends upon for any call and it does not include functions to reset to a known state. That means you should not mix SDL_Renderer with OpenGL yet.
However, if you really want this functionality now, you can try SDL_gpu (note: I'm the author). It does support mixing with OpenGL calls and custom shaders. You would want to specify which version of the OpenGL API you need (e.g. with GPU_InitRenderer(GPU_RENDERER_OPENGL_1, ...)) and reset the GL state that SDL_gpu uses each frame (GPU_ResetRendererState()). Check out the 3d demo in the SDL_gpu source repository for more.
https://github.com/grimfang4/sdl-gpu/blob/master/demos/3d/main.c
You can render to an SDL_Surface with SDL, and then convert it to a texture & upload it to the GPU using OpenGL.
Example code: http://www.sdltutorials.com/sdl-tip-sdl-surface-to-opengl-texture
I've looked at a ton of articles and SO questions about OpenGL not drawing, common mistakes, etc. This one is stumping me.
I've tried several different settings for glOrtho, different vertex positions, colors, etc., all to no avail.
I can confirm the OpenGL state is valid because the clear color is purple in the code (meaning the window is purple). gDEBugger is also confirming frames are being updated (so is Fraps).
Here is the code. Lines marked as "didn't help" were not there originally, and were things that I tried and failed.
QTWindow::QTWindow( )
{
// Enable mouse tracking
this->setMouseTracking(true);
}
void QTWindow::initializeGL()
{
// DEBUG
debug("Init'ing GL");
this->makeCurrent(); ///< Didn't help
this->resizeGL(0, 0); ///< Didn't help
glDisable(GL_CULL_FACE); ///< Didn't help
glClearColor(1, 0, 1, 0);
}
void QTWindow::paintGL()
{
// DEBUG
debug("Painting GL");
this->makeCurrent(); ///< Didn't help
glLoadIdentity();
glClear(GL_COLOR_BUFFER_BIT);
glColor3f(0,1,1);
glBegin(GL_TRIANGLES);
glVertex2f(500,100);
glVertex2f(100,500);
glVertex2f(0,0);
glEnd();
this->swapBuffers(); ///< Didn't help
}
void QTWindow::resizeGL(int width, int height)
{
// DEBUG
debug("Resizing GL");
this->makeCurrent(); ///< Didn't help
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(0, 1000, 0, 1000, -1, 1);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
}
The triangle is not being displayed at all, even with culling turned off. However, all three debug logs are called exactly how they should be.
What am I missing?
Try calling glViewport() function at the very beginning of the QTWindow::resizeGL() function:
glViewport(0, 0, width, height);
And don't ever call resizeGL() with width and height set to 0 ;) Besides that, it is not necessary for you to call resizeGL() directly as it is being called by Qt whenever the window is being resized.
You can remove all calls to the swapBuffers() function - it is being called internally by Qt.
The makeCurrent() function should be called before all other GL calls, so it is good that you have called it in initializeGL(), but you don't have to call it in the paintGL() function (unless paintGL() is being called from another thread, but I bet it isn't in your code).
The issue ended up being versions. The version string returned with glGetString(GL_VERSION) indicated 4.2 compatibility context was being used.
Since the triangle calls in the paintGL method were removed in 3.1 (if I recall correctly), it was obvious why they weren't drawing anything. Further, no errors were being thrown because it was in compat. mode.
Because I couldn't get the version down below 3.0 on the QGLWidget (due to the fact that QT requires 2.1, as I was informed on another message board), I set the version to 3.0 and tried using some 3.0 drawing calls and it ended up working.
I work on an MFC app containing OpenGL context.I am new to MFC that is why I am asking it.OpenGL works fine ,but when I want to draw a text above the 3D window using this code inside WindowProc:
case WM_PAINT:
hDC=BeginPaint(window,&paintStr);
GetClientRect(window,&aRect);
SetBkMode(hDC,TRANSPARENT);
DrawText(hDC,L"He He I am a text on top of OpenGL",-1,&aRect,DT_SINGLELINE|DT_CENTER|DT_VCENTER);
EndPaint(window,&paintStr);
return 0;
it is shown beneath the OpenGL context.I can see it only when resizing the window as the OpenGL rendering pauses than.
What you're doing is wrong and also harder than doing it all in OpenGL. To solve the problem of adding text to an OpenGL-drawn window, it's better to just make OpenGL draw the text. You can even use the exact same font you were using in MFC by creating a CFont instance when you handle WM_CREATE, selecting the font into the DC, and calling wglUseFontBitmaps, which will make a series of rasterized bitmaps that you can use with glCallLists. (While you're at it, call GetCharABCWidths and GetTextMetrics to determine the width and height of each glyph, respectively.)
ABC glyphInfo[256]; // for font widths
TEXTMETRIC tm; // for font heights
// create a bitmap font
CFont myFont;
myFont.CreateFont(
16, // nHeight
0, // nWidth
0, // nEscapement
0, // nOrientation
FW_NORMAL, // nWeight
FALSE, // bItalic
FALSE, // bUnderline
0, // cStrikeOut
ANSI_CHARSET, // nCharSet
OUT_DEFAULT_PRECIS, // nOutPrecision
CLIP_DEFAULT_PRECIS, // nClipPrecision
DEFAULT_QUALITY, // nQuality
DEFAULT_PITCH | FF_SWISS, // nPitchAndFamily
_T("Arial") // lpszFacename
);
// change the current font in the DC
CDC* pDC = CDC::FromHandle(hdc);
// make the system font the device context's selected font
CFont *pOldFont = (CFont *)pDC->SelectObject (&myFont);
// the display list numbering starts at 1000, an arbitrary choice
wglUseFontBitmaps (hdc, 0, 255, 1000);
VERIFY( GetCharABCWidths (hdc, 0, 255, &glyphInfo[0]) );
pDC->GetTextMetrics(&tm);
if(pOldFont)
pDC->SelectObject(pOldFont);
myFont.DeleteObject();
Then when you handle WM_PAINT, reset your matrices and use glRasterPos2d to put the text where you need it to go. I suggest calculating the exact width of your string using code similar to the one below if you want it to be horizontally centered.
// indicate start of glyph display lists
glListBase (1000);
CRect r;
GetWindowRect(r);
glMatrixMode(GL_PROJECTION);
glPushMatrix();
glLoadIdentity();
gluOrtho2D(0, r.Width(), 0, r.Height());
glMatrixMode(GL_MODELVIEW);
glPushMatrix();
glLoadIdentity();
CString formattedString;
formattedString.Format("Pi is about %1.2f", 3.1415);
int stringWidth=0; // pixels
for(int j=0; j < formattedString.GetLength(); ++j)
stringWidth += glyphInfo[ formattedString.GetAt(j) ].abcA + glyphInfo[ formattedString.GetAt(j) ].abcB + glyphInfo[ formattedString.GetAt(j) ].abcC;
double textXPosition, textYPosition;
textXPosition = r.Width()/2-stringWidth/2; // horizontally centered
textYPosition = r.Height()/2-tm.tmHeight/2; // vertically centered
glRasterPos2d(textXPosition,textYPosition);
// this is what actually draws the text (as a series of rasterized bitmaps)
glCallLists (formattedString.GetLength(), GL_UNSIGNED_BYTE, (LPCSTR)formattedString);
glMatrixMode(GL_MODELVIEW);
glPopMatrix();
glMatrixMode(GL_PROJECTION);
glPopMatrix();
While the setup is annoying, you only have to do it once, and I think it's less frustrating than dealing with GDI. Mixing GDI and OpenGL is really asking for trouble, and OpenGL does a very good job of displaying text -- you get sub-pixel accuracy for free, among other benefits.
Edit: In response to your request for including GUI elements, I will assume that you meant that you want to have both OpenGL-drawn windows and also standard Windows controls (edit boxes, check boxes, buttons, list controls, etc.) inside the same parent window. I will also assume that you intend OpenGL to draw only part of the window, not the background of the window.
Since you said you're using MFC, I suggest that you create a dialog window, add all of your standard Windows controls to it, and then add in a CWnd-derived class where you handle WM_PAINT. Use the resource editor to move the control to where you want it. Effectively, you're making an owner-draw custom control where OpenGL is doing the drawing. So OpenGL will draw that window, and the standard MFC classes (CEdit, CButton, etc.) will draw themselves. This works well in my experience, and it's really not much different from what GDI does in an owner-draw control.
What if instead you want OpenGL to draw the background of the window, and you want standard Windows controls to appear on top of it? I don't think this is a great idea, but you can handle WM_PAINT and WM_ERASE for your CDialog-derived class. In WM_ERASE, call OpenGL to draw your 3D content, which will be overwritten by the standard Windows controls when WM_PAINT is called. Alternatively in WM_PAINT you could call OpenGL before calling CDialog::OnDraw, which would be similar.
Please clarify your statement "I want to add some 2s graphics overlay (like labels ,gui elements)" if you want me to write more.
Looking at your code I assume the OpenGL rendering is called from a timer or as idel loop action. Naturally OpenGL execution will probably contain some clearing, thus taking anything else drawn with it.
Mixing GDI text drawing with OpenGL is not recommended, but can be done. But of course you then need to include that code into the OpenGL drawing function, too, placing all GDI operations after the buffer swap.
I am trying to display HUD over my 3D game. For starters, I am just trying to display "Hello World", but I haven't had any success yet! The scene freezes / flickers once I am done.
I am using Qt/C++ and QGLWdiget / QPainter to get this done. I have used overpainting example as my reference to get started. Here is what I do:
override paintEvent(...) in my own subclassed GameGL Class ( GameGL : public QGLWidget )
Push openGL ModelView matrix as the current matrix
enable parameters as gl_depth_test
render my game (:: paintGL1() )
disable the modelview parameters
pop modelview matrix
Make QPainter object
invoke paint.drawText()
Flush using paint.end()
This is pretty much the same as mentioned in the example. However, when I run this code, it experiences freezing / flickering and is highly un-responsive. Would anyone have any idea as to why this might be happening ? I'd really appreaciate any help.
Code:makeCurrent();
glMatrixMode(GL_MODELVIEW);
glPushMatrix();
//Black background
glClearColor(0.0f, 0.0f, 0.0f, 1.0f);//.50f, 1.0f );
//glShadeModel(GL_SMOOTH);
glEnable(GL_DEPTH_TEST);
//glEnable(GL_CULL_FACE);
glEnable(GL_LIGHTING);
m_pLight->SetupLight(GL_AMBIENT | GL_DIFFUSE | GL_SPECULAR);
glEnableClientState( GL_INDEX_ARRAY );
glEnableClientState( GL_VERTEX_ARRAY );
resizeGL( width(), height() );
paintGL1();
//glShadeModel(GL_FLAT);
glDisable(GL_DEPTH_TEST);
//glDisable(GL_CULL_FACE);
glDisable(GL_LIGHTING);
glDisableClientState( GL_INDEX_ARRAY );
glDisableClientState( GL_VERTEX_ARRAY );
glMatrixMode(GL_MODELVIEW);
glPopMatrix();
QPainter painter(this);
painter.setRenderHint(QPainter::Antialiasing);
painter.drawText(100, 50, QString("Hello"));
painter.end();
Thank you
For anyone who is still struggling with this and came across this post: here is how I solved it::
Please follow the overpainting example as is. If you look over at the code in the example, you would notice in the constructor, a timer timeout() SIGNAL is connected to animate() SLOT. If you look closely at the animate() slot, it in-turn calls update() a.k.a GLWidget::update(). If you follow the documentation for GLWidget::update(); this in-turn calls paintEvent(...).
This background is important and was the missing piece to my problem. I was earlier using paintGL(...) to draw my scene since I had overriden GLWidget. To support animation or updates to my scene, I had connected the timer to updateGL(). This was in-turn invoking paintGL() via glDraw(). This was the root cause of all the problems.
The code as I had written was calling paintGL() again and again. Following overpainting example, I got rid of paintGL method completely and switched to paintEvent(...) rendering methodology instead. Thus, to keep things in-sync, I had to call update() (instead of updateGL() ) to make things work. The minute I made this transition, things started working as expected. (GLWidget::update() calls paintEvent(...) )
I hope it has helped you any bit. If it still doesn't work for you or need firther explanaition, leave me a comment here and I will try to help.
I'm using win32 and opengl and I have a window set up with the projection at glOrtho of the window's coordinates. I have double buffering enabled, tested it with glGet as well. My program always seems to tear any primitives that I try to draw on it if it's being constantly translated.
Here is my OpenGL initialization function:
glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
glViewport(0, 0, 640, 480);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(0, 640, 0, 480, 0, 100);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glDrawBuffer(GL_BACK);
glLoadIdentity();
And this is my rendering function, gMouseX and gMouseY are the coordinates of the mouse:
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glTranslatef(gMouseX, gMouseY, 0.0f);
glColor3f(0.5f, 0.5f, 0.5f);
glBegin(GL_TRIANGLES);
glVertex2f(0.0f, 128.0f);
glVertex2f(128.0f, 0.0f);
glVertex2f(0.0f, 0.0f);
glEnd();
SwapBuffers(hDC);
The same tearing problem occurs regardless of how often the rendering function runs. Is there something I'm doing wrong or missing here?
If you're just rendering one or two trianges, you're going to have an insanely high framerate (in the thousands of FPS probably), which means it's SwapBuffering like hell, which means you're probably always swapping during the screen refresh (even with double buffering on). Once your scene gets going with more content and the framerate falls to more realistic values, it should stop tearing. Alternatively, look in to enabling V-Sync, such as with wglSwapIntervalEXT on Windows.
This issue doesn't have to be strictly connected to VSync, as all people around the internet try to suggest. In my case the problem was caused by the way in which the window was initialized. I noticed, that getting rid off dwStyle=WS_POPUP solved the problem, but only partially because then the window wasn't in the fullscreen mode. What worked for me in the end was using SetWindowLong(hwnd, GWL_STYLE, 0); after creating the window. It basically clears the window style. So my code for initializing the window looks like that:
dwStyle=WS_POPUP; //Windows Style
ShowCursor(FALSE); //Hide Mouse Pointer
//Create the Window
hwnd= CreateWindowEx(NULL,
"GLClass",
appName,
dwStyle,
0, 0,
(long)windowWidth,
(long)windowHeight,
NULL,
NULL,
hInstance,
NULL);
SetWindowLong(hwnd, GWL_STYLE, 0);
After this modification all my problems with tearing and also not being able to PrintScreen, were solved. I didn't need to touch VSync anywhere.
When defining your win32 application window styles, don't include WS_POPUP
After debugging a problem where full screen would introduce screen tearing, I discovered the styles for full screen, after removing WS_POPUP it seemed to have stop tearing single handedly, without having to force the rendering loop to the refresh rate. WS_POPUP is known for being problematic, I guess. It would also block any full screen screenshots to complete white.
Tearing is caused by not synchronizing your updates with the monitor's vertical blanking interval. It's a bit hardware dependent in OpenGL (I think, not an expert), start with looking for glXWaitVideoSyncSGI. Googling "opengl sync to vblank" pays off too.
Try to putting a cap / limiting on the frame rate or yielding it probably (if you don't have a vsync):
Here is the pseudo code:
let tick equals new_tick
if tick is less than last_tick do
yield
done
calculate last_tick
Try the sleep function and setting it to one, so to yield:
Sleep(1);
Also remember limiting or capping frame rate is not that advisable as there is certain functions that are really meant for reducing frame calculations.