Sign in to follow this  
wisteria23

OpenGL How to render text on Opengl ES 2.0 in Qt 4.7

Recommended Posts

wisteria23    100
Hi,
We want to draw date and Time on Opengl ES 2.0 context in QT 4.7.
We have tried doing so using drawText(x,y,Qstring).
following is the code attached for reference.
QPainter painter;
painter.begin( this );
painter.setPen(Qt::red);
painter.drawText(-6.0f,6.0f,QString("Example"));
But it is not being drawn on the Opengl ES context.

We are inheriting this widget class from QGLWidget.
Is this the correct way or there is some other way to draw date and Time on the opengl ES 2.0 context?
Please suggest or provide some link for reference.

Regards,
wisty

Share this post


Link to post
Share on other sites
Kambiz    758
Quote:
Original post by wisteria23
painter.drawText(-6.0f,6.0f,QString("Example"));

There is no drawText function which takes two floats. Are you sure the coordinate (-6,6) is on the screen?
What is the this is painter.begin( this ) ? Is it the QGLWidget?
Are you use beginNativePainting and endNativePainting when calling OGL functions your self? If you forget that will mess up the rendering of Qt.

Share this post


Link to post
Share on other sites
wisteria23    100
Hi Kambiz,

We are doing all the rendering in paintGL function.
In this function we are calling painter.begin(this) which is QGLWidget.

We are also calling beginNativePainting and endNativePainting when calling OGL functions.

Also we are giving this ( -6,6) coordinates after considering the positions where we are rendering other objects.

Is there some other Qt class which we can use to render Date and Time?
I know this is not a Qt forum,but in case someone has worked in Qt using Opengl ES 2.0,it would be of great help.

Regards,
wisty

Share this post


Link to post
Share on other sites
Kambiz    758
I have no experience with OpenGL ES but I had no trouble with Qt and OpenGL up to now. Do the other painting functions work? If yes, maybe there is a problem with loading the font.

Also, where do you draw other objects? (-6,6) may be on screen in the coordinate system of QGraphicsView (if you are using one) but no in the coordinate system of the QGLWidget. How do you setup the coordinate system?

What does QPainter::clipRegion() return? (You can use QRegion::boundingRect() to get the bounding rectangle of the clip region)

Quote:
Original post by wisteria23
Is there some other Qt class which we can use to render Date and Time?
I know this is not a Qt forum,but in case someone has worked in Qt using Opengl ES 2.0,it would be of great help.

Yes, in our engine we use a wrapper around QGraphicsTextItem to display text on the screen. You can find an example of the required wrapper in the boxes demo but I'm pretty sure that the text still get's rendered the same way.

Share this post


Link to post
Share on other sites
wisteria23    100
HI Kambiz,
Thank you so much for your prompt reply.
I am not sure where the exact problem is.
we are getting all other rendering in place.But only when we try to draw the text, we are not able to render it.
Right now we are giving some random coordinates(based on other drawing coordinates) so that it is atleast visible on the screen.But till now there is no success..

Is there something called as Bitmap font rendering in Qt?

Regards,
wisty

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

Sign in to follow this  

  • Similar Content

    • By markshaw001
      Hi i am new to this forum  i wanted to ask for help from all of you i want to generate real time terrain using a 32 bit heightmap i am good at c++ and have started learning Opengl as i am very interested in making landscapes in opengl i have looked around the internet for help about this topic but i am not getting the hang of the concepts and what they are doing can some here suggests me some good resources for making terrain engine please for example like tutorials,books etc so that i can understand the whole concept of terrain generation.
       
    • By KarimIO
      Hey guys. I'm trying to get my application to work on my Nvidia GTX 970 desktop. It currently works on my Intel HD 3000 laptop, but on the desktop, every bind textures specifically from framebuffers, I get half a second of lag. This is done 4 times as I have three RGBA textures and one depth 32F buffer. I tried to use debugging software for the first time - RenderDoc only shows SwapBuffers() and no OGL calls, while Nvidia Nsight crashes upon execution, so neither are helpful. Without binding it runs regularly. This does not happen with non-framebuffer binds.
      GLFramebuffer::GLFramebuffer(FramebufferCreateInfo createInfo) { glGenFramebuffers(1, &fbo); glBindFramebuffer(GL_FRAMEBUFFER, fbo); textures = new GLuint[createInfo.numColorTargets]; glGenTextures(createInfo.numColorTargets, textures); GLenum *DrawBuffers = new GLenum[createInfo.numColorTargets]; for (uint32_t i = 0; i < createInfo.numColorTargets; i++) { glBindTexture(GL_TEXTURE_2D, textures[i]); GLint internalFormat; GLenum format; TranslateFormats(createInfo.colorFormats[i], format, internalFormat); // returns GL_RGBA and GL_RGBA glTexImage2D(GL_TEXTURE_2D, 0, internalFormat, createInfo.width, createInfo.height, 0, format, GL_FLOAT, 0); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST); DrawBuffers[i] = GL_COLOR_ATTACHMENT0 + i; glBindTexture(GL_TEXTURE_2D, 0); glFramebufferTexture(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0 + i, textures[i], 0); } if (createInfo.depthFormat != FORMAT_DEPTH_NONE) { GLenum depthFormat; switch (createInfo.depthFormat) { case FORMAT_DEPTH_16: depthFormat = GL_DEPTH_COMPONENT16; break; case FORMAT_DEPTH_24: depthFormat = GL_DEPTH_COMPONENT24; break; case FORMAT_DEPTH_32: depthFormat = GL_DEPTH_COMPONENT32; break; case FORMAT_DEPTH_24_STENCIL_8: depthFormat = GL_DEPTH24_STENCIL8; break; case FORMAT_DEPTH_32_STENCIL_8: depthFormat = GL_DEPTH32F_STENCIL8; break; } glGenTextures(1, &depthrenderbuffer); glBindTexture(GL_TEXTURE_2D, depthrenderbuffer); glTexImage2D(GL_TEXTURE_2D, 0, depthFormat, createInfo.width, createInfo.height, 0, GL_DEPTH_COMPONENT, GL_FLOAT, 0); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST); glBindTexture(GL_TEXTURE_2D, 0); glFramebufferTexture(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, depthrenderbuffer, 0); } if (createInfo.numColorTargets > 0) glDrawBuffers(createInfo.numColorTargets, DrawBuffers); else glDrawBuffer(GL_NONE); if (glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE) std::cout << "Framebuffer Incomplete\n"; glBindFramebuffer(GL_FRAMEBUFFER, 0); width = createInfo.width; height = createInfo.height; } // ... // FBO Creation FramebufferCreateInfo gbufferCI; gbufferCI.colorFormats = gbufferCFs.data(); gbufferCI.depthFormat = FORMAT_DEPTH_32; gbufferCI.numColorTargets = gbufferCFs.size(); gbufferCI.width = engine.settings.resolutionX; gbufferCI.height = engine.settings.resolutionY; gbufferCI.renderPass = nullptr; gbuffer = graphicsWrapper->CreateFramebuffer(gbufferCI); // Bind glBindFramebuffer(GL_DRAW_FRAMEBUFFER, fbo); // Draw here... // Bind to textures glActiveTexture(GL_TEXTURE0); glBindTexture(GL_TEXTURE_2D, textures[0]); glActiveTexture(GL_TEXTURE1); glBindTexture(GL_TEXTURE_2D, textures[1]); glActiveTexture(GL_TEXTURE2); glBindTexture(GL_TEXTURE_2D, textures[2]); glActiveTexture(GL_TEXTURE3); glBindTexture(GL_TEXTURE_2D, depthrenderbuffer); Here is an extract of my code. I can't think of anything else to include. I've really been butting my head into a wall trying to think of a reason but I can think of none and all my research yields nothing. Thanks in advance!
    • By Adrianensis
      Hi everyone, I've shared my 2D Game Engine source code. It's the result of 4 years working on it (and I still continue improving features ) and I want to share with the community. You can see some videos on youtube and some demo gifs on my twitter account.
      This Engine has been developed as End-of-Degree Project and it is coded in Javascript, WebGL and GLSL. The engine is written from scratch.
      This is not a professional engine but it's for learning purposes, so anyone can review the code an learn basis about graphics, physics or game engine architecture. Source code on this GitHub repository.
      I'm available for a good conversation about Game Engine / Graphics Programming
    • By C0dR
      I would like to introduce the first version of my physically based camera rendering library, written in C++, called PhysiCam.
      Physicam is an open source OpenGL C++ library, which provides physically based camera rendering and parameters. It is based on OpenGL and designed to be used as either static library or dynamic library and can be integrated in existing applications.
       
      The following features are implemented:
      Physically based sensor and focal length calculation Autoexposure Manual exposure Lense distortion Bloom (influenced by ISO, Shutter Speed, Sensor type etc.) Bokeh (influenced by Aperture, Sensor type and focal length) Tonemapping  
      You can find the repository at https://github.com/0x2A/physicam
       
      I would be happy about feedback, suggestions or contributions.

    • By altay
      Hi folks,
      Imagine we have 8 different light sources in our scene and want dynamic shadow map for each of them. The question is how do we generate shadow maps? Do we render the scene for each to get the depth data? If so, how about performance? Do we deal with the performance issues just by applying general methods (e.g. frustum culling)?
      Thanks,
       
  • Popular Now