I am using wxGLContext and wxGLCanvas for 3D visualization. I initialized opengl like this
SetCurrent(*canvas);
glEnable(GL_BLEND);
glEnable(GL_CULL_FACE);
glEnable(GL_DEPTH_TEST);
glEnable(GL_LIGHTING);
glEnable(GL_COLOR_MATERIAL);
and draw the objects
glClear(GL_DEPTH_BUFFER_BIT | GL_COLOR_BUFFER_BIT);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(-w, w, -h, h, -10.0f, 10.0f);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
quad = gluNewQuadric();
glPolygonMode( GL_FRONT_AND_BACK, GL_FILL);
//draw the objects
gluDeleteQuadric(quad);
glFlush();
The problem is that this code works fine in windows, but in ubuntu the objects clipped by the objects which are located in back. The glFrontFace is correct for all objects, but clipping is wrong.
As HolyBlackCat mentioned in the comments,
the problem was depth buffer for the wxGLContext.
It works by using WX_GL_DEPTH_SIZE 8 and 16, but not 32.
Although, I still do not know, how windows can handle it without error, I corrected some lines as follows
int AttribList[] = {WX_GL_DOUBLEBUFFER, WX_GL_DEPTH_SIZE, 16, 0};
wxGLCanvas* glc = new wxGLCanvas(parent, wxID_ANY, AttribList,
wxDefaultPosition, wxDefaultSize,
wxFULL_REPAINT_ON_RESIZE);
and now it works for both OSs.
Related
I'm using QGLWidget and this code to draw a text on the screen but the rendering is catastrophic if the string's length is too high :
Here's my code :
glPushMatrix();
glRotatef(90, 0, 0, 1);
QString qStr = QString("Here's a very long string which doesn't mean anything at all but had some rendering problems");
renderText(0.0, 0.0, 0.0, qStr);
glPopMatrix();
I had the exact same problem when using Helvetica. Changing the font to Arial solved it.
I did a small wrapper around it to make things easier:
void _draw_text(double x, double y, double z, QString txt)
{
glDisable(GL_LIGHTING);
glDisable(GL_DEPTH_TEST);
qglColor(Qt::white);
renderText(x, y, z, txt, QFont("Arial", 12, QFont::Bold, false) );
glEnable(GL_DEPTH_TEST);
glEnable(GL_LIGHTING);
}
From the documentation:
This function can only be used inside a QPainter::beginNativePainting()/QPainter::endNativePainting() block if the default OpenGL paint engine is QPaintEngine::OpenGL. To make QPaintEngine::OpenGL the default GL engine, call QGL::setPreferredPaintEngine(QPaintEngine::OpenGL) before the QApplication constructor.
Hence, have you tried to use QPainter::beginNativePainting() just before the call, and QPainter::endNativePainting() just after?
Also, note that the text is rendered in window coordinate, not taking into account at all your current OpenGL matrix state (in short, your glRotatef(90, 0, 0, 1) call has no effect). You can see in the implementation here that they save your current OpenGL state by calling qt_save_gl_state(), then create their brand new matrices with:
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glViewport(0, 0, width, height);
glOrtho(0, width, height, 0, 0, 1);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
Then draw the text, and finally restore your previous OpenGL state with qt_restore_gl_state()
I am attempting to make a simple drawing using openGL. However, the depth buffer doesn't appear to be working.
Other people with a similar problem are typically doing one of two things wrong:
Not including glEnable(GL_DEPTH_TEST)
Bad clipping values
However, my code does not have either of these problems.
...
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
gluPerspective(25.0,1.0,10.0,200.0);
// Set the camera location
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
gluLookAt(20.0, 10.0, 50.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0);
// Enable depth test
glEnable(GL_DEPTH_TEST);
// Cull backfacing polygons
glCullFace(GL_BACK);
glEnable(GL_CULL_FACE)
drawCoordinateAxis();
drawBox(5.0,2.0,5.0,0.8,0.0,0.0);
glTranslated(1.0,-1.0,1.0); //The box is 5x2x5, it is shifted 1 unit down and 1 in the x and z directions
drawBox(5.0,2.0,5.0,0.0,1.0,1.0);
...
When I execute my code, this is drawn. http://imgur.com/G9y41O1
Note that the blue box and the red box collide, so the red box should be covering part of the blue box.
The functions drawCoordinateAxis() and drawBox() just draw a few primitives, nothing fancy inside.
I am running this on Debian squeeze.
void reshape(GLint width, GLint height)
{
g_Width = width;
g_Height = height;
glViewport(0, 0, g_Width, g_Height);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluPerspective(65.0, (float)g_Width / g_Height, g_nearPlane, g_farPlane);
glMatrixMode(GL_MODELVIEW);
}
So set Matrix Mode to GL_PROJECTION first, then gluPerspective.... and then back to MODELVIEW mode.
Hey all, I'm very new to OpenGL (just started seriously programming with it today) and I'm trying to use it to give my SDL games a 3D boost. I've setup a small test program below:
#include <SDL/SDL.h>
#include <gl/gl.h>
int main(int argc, char *argv[])
{
SDL_Event event;
float theta = 0.0f;
SDL_Init(SDL_INIT_VIDEO);
SDL_Surface *screen = SDL_SetVideoMode(800, 600, 32, SDL_OPENGL | SDL_HWSURFACE | SDL_RESIZABLE | SDL_FULLSCREEN);
glViewport(0, 0, 800, 600);
glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
glClearDepth(1.0);
glDepthFunc(GL_LESS);
glEnable(GL_DEPTH_TEST);
glShadeModel(GL_SMOOTH);
glMatrixMode(GL_PROJECTION);
glMatrixMode(GL_MODELVIEW);
int done;
for(done = 0; !done;)
{
SDL_FillRect(screen, 0, SDL_MapRGB(screen->format, 255, 0, 0));
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glLoadIdentity();
glTranslatef(0.0f,0.0f,0.0f);
glRotatef(theta, 0.0f, 0.0f, 1.0f);
glBegin(GL_TRIANGLES);
glColor3f(0.83f, 0.83f, 0.0f);
glVertex2f(0.0f, 1.0f);
glColor3f(0.83f, 0.83f, 0.0f);
glVertex2f(0.87f, -0.5f);
glColor3f(0.83f, 0.83f, 0.0f);
glVertex2f(-0.87f, -0.5f);
glEnd();
theta += 10.0f;
SDL_Flip(screen);
SDL_GL_SwapBuffers();
SDL_PollEvent(&event);
if(event.key.keysym.sym == SDLK_ESCAPE)
done = 1;
}
}
My problem is that the red background I'm trying to rendered is never rendered, only the OpenGL Triangle is rendered.
Thanks in advance to anyone who can help me. It's much appreciated.
There's one simple rule about OpenGL: It doesn't play well with others. What happens in your case is, that the double buffer swap (initiated by SDL_GL_SwapBuffers) will in some way replace everything in the window, not being rendered by OpenGL.
Just draw everything using OpenGL.
You fill the back buffer on one line with SDL_FillRect then you clear it on the next with glClear. Have you tried swapping the order of the operations?
Not that I disagree with the accepted answer; in general trying to mix software rendering methods with OpenGL is a recipe for confusion at best, but you might get lucky in this case.
As for rending textured quads, you should be able to work it out from NeHe lesson 6. People complain about NeHe but it's a reasonable guide for getting started. Just don't use it as an example of good coding or of efficient modern OpenGL usage. Start here and move to more complex stuff later.
If you're using C++, SFML library might be a better option (it has C bindings though, but haven't tried those). It plays nicely with OpenGL and has functions to cooperatively work alongside GL. As far as I understood it, SFML functions themselves use GL to render. Although, I do suggest that you do rendering only with GL calls as noted above.
your SDL_FillRect isn't show as red, because you call glClear with GL_COLOR_BUFFER_BIT set afterwards
For my last few projects I have been using some of the utility files that I found whilst looking at a few demos here.
Namely a file called opengl.h - mainly used to manage shaders a bit like glew and another file gl_font.
gl_font is a class they use to render fonts on screen using vertex buffer objects.
However, when I use this to render the framerate in my game it draws everything but the skybox correctly. For some reason the skybox is rendered white as seen here, if I do not render the font it looks like this.
Here are some parts of the gl_font class that I think are most important:
void GLFont::begin()
{
HWND hWnd = GetForegroundWindow();
RECT rcClient;
GetClientRect(hWnd, &rcClient);
int w = rcClient.right - rcClient.left;
int h = rcClient.bottom - rcClient.top;
glPushAttrib(GL_CURRENT_BIT | GL_LIGHTING_BIT);
glDisable(GL_LIGHTING);
glEnable(GL_BLEND);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
glEnable(GL_TEXTURE_2D);
glBindTexture(GL_TEXTURE_2D, m_fontTexture);
glMatrixMode(GL_PROJECTION);
glPushMatrix();
glLoadIdentity();
glOrtho(0.0f, w, h, 0.0f, -1.0f, 1.0f);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glBindBuffer(GL_ARRAY_BUFFER, m_vertexBuffer);
drawTextBegin();
}
I have trie changing glPushAttrib(GL_CURRENT_BIT | GL_LIGHTING_BIT); to glPushAttrib(GL_CURRENT_BIT | GL_LIGHTING_BIT | GL_TEXTURE_BIT); and the background texture returns, but the font isn't rendered.
void GLFont::end()
{
drawTextEnd();
glBindBuffer(GL_ARRAY_BUFFER, 0);
glBindTexture(GL_TEXTURE_2D, 0);
glDisable(GL_TEXTURE_2D);
glDisable(GL_BLEND);
glMatrixMode(GL_PROJECTION);
glPopMatrix();
glMatrixMode(GL_MODELVIEW);
glPopMatrix();
glPopAttrib();
}
This is an image of the depth buffer when the font is rendered and this is what is looks like when it is not.
Could anyone shed some light on this problem please?
Any help would be much appreciated!
Thanks.
Looks like begin() lacks a glPushMatrix() after glMatrixMode(GL_MODELVIEW). This might cause the scene to be rendered incorrectly when some text is also rendered.
Didn't glGetError() report a GL_STACK_UNDERFLOW error?
I'm in the process of writing a wrapper for some OpenGL functions. The goal is to wrap the context used by the game Neverwinter Nights, in order to apply post-processing shader effects. After learning OpenGL (this is my first attempt to use it) and much playing with DLLs and redirection, I have a somewhat working system.
However, when the post-processing fullscreen quad is active, all texturing and transparency drawn by the game are lost. This shouldn't be possible, because all my functions take effect after the game has completely finished its own rendering.
The code does not use renderbuffers or framebuffers (both refused to compile on my system in any way, with or with GLEW or GLee, despite being supported and usable by other programs). Eventually, I put together this code to handle copying the texture from the buffer and rendering a fullscreen quad:
extern "C" SEND BOOL WINAPI hook_wglSwapLayerBuffers(HDC h, UINT v)
{
if ( frameCount > 250 )
{
frameCount++;
if ( frameCount == 750 ) frameCount = 0;
if ( nwshader->thisframe == NULL )
{
createTextures();
}
glBindTexture(GL_TEXTURE_2D, nwshader->thisframe);
glCopyTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, 0, 0, nwshader->width, nwshader->height, 0);
glClearColor(0.0f, 0.5f, 0.0f, 0.5f);
glClear(GL_COLOR_BUFFER_BIT);
glEnable(GL_TEXTURE_2D);
glDisable(GL_DEPTH_TEST);
glBlendFunc(GL_ONE, GL_ZERO);
glEnable(GL_BLEND);
glMatrixMode(GL_PROJECTION);
glPushMatrix();
glLoadIdentity();
glOrtho( 0, nwshader->width , nwshader->height , 0, -1, 1 );
glMatrixMode(GL_MODELVIEW);
glPushMatrix();
glLoadIdentity();
glColor4f(1.0f, 1.0f, 1.0f, 1.0f);
glBegin(GL_POLYGON);
glTexCoord2f(0.0f, 1.0f);
glVertex2d(0, 0);
glTexCoord2f(0.0f, 0.0f);
glVertex2d(0, nwshader->height);
glTexCoord2f(1.0f, 0.0f);
glVertex2d(nwshader->width, nwshader->height);
glTexCoord2f(1.0f, 1.0f);
glVertex2d(nwshader->width, 0);
glEnd();
glMatrixMode( GL_PROJECTION );
glPopMatrix();
glMatrixMode( GL_MODELVIEW );
glPopMatrix();
glEnable(GL_DEPTH_TEST);
glDisable(GL_TEXTURE_2D);
glBindTexture(GL_TEXTURE_2D, 0);
} else {
frameCount++;
}
if ( h == grabbedDevice )
{
Log->logline("Swapping buffer on cached device.");
}
return wglSwapLayerBuffers(h,v);
}
This code functions almost functions perfectly and has no notable slow-down. However, when it is active (I added the frameCount condition to turn it on and off every ~5 seconds), all alpha and texturing are completely ignored by the game renderer. I'm not turning off any kind of blending or texturing before this function (the only OpenGL calls are to create the nwshader->thisframe texture).
I was able to catch a few screenshots of what's happening:
Broken A: http://i4.photobucket.com/albums/y145/peachykeen000/outside_brokenA.png
Broken B: http://i4.photobucket.com/albums/y145/peachykeen000/outside_brokenB.png
(note, in B, the smoke in the back is not broken, it is correctly transparent. So is the HUD.)
Broken Interior: http://i4.photobucket.com/albums/y145/peachykeen000/transparency_broken.png
Correct Interior (for comparison): http://i4.photobucket.com/albums/y145/peachykeen000/transparency_proper.png
The drawing of the quad also breaks menus, turning the whole thing into a black surface with a single white box. I suspect it is a problem with either depth or how the game is drawing certain objects, or a state that is not being reset properly. I've used GLintercept to dump a full log of all calls in a frame, and didn't see anything wrong (the call to wglSwapLayerBuffers is always last).
Being brand new to working with OpenGL, I really have no clue what's going wrong (or how to fix it) and nothing I've tried has helped. What am I missing?
I don't quite understand how your code is supposed to integrate with the Neverwinter Nights code. However...
It seems like you're most likely changing some setting that the existing code didn't expect to change.
Based on the description of the problem, I'd try removing the following line:
glDisable(GL_TEXTURE_2D);
That line disables textures, which certainly sounds like the problem you're seeing.