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Screen Dark working with FBOs

enzo sacchi
Note: This was originally posted on 7th November 2010 at http://forums.arm.com

Hi Guys,

Trying to port an akready well running Sw from Fedora PC to the Mali400 on ST7108 chip, with GLES-2.0, I got a problem working with Framebuffer Objects.
Everything is ok, debugging ok, framebuffer objects completes, no errors, but the screen remains completely dark.
My environment on Mali/ST7108 is OK, other applications can run nicely.

But I think to have not completely understood (or better: not understood at all) how to set display and surfaces while working woth FBOs (maybe the problem could be also found somewhere else)

Basic setting is more or less as below, where I have put only the relevant setting and call for Display and Surfaces.

In does seem that the eglSwapBuffers does't work at all while working with FBOs
(even a monocolor screen cannot be seen...).
In contrast, while working out of FBOs, everything seems to be ok.

After binding with glBindFramebuffer(GL_FRAMEBUFFER,0), then everything is working and can be displayed.

In contrast, after glBindFramebuffer(GL_FRAMEBUFFER, framebuffer), I cannot see anything after he eglSwapBuffers, even if the debug seems to be ok.

Could someone pls help me in giving me suggestions on how to properly set Display and Surfaces?
Does there is a running examples while using FBOs on ST7108 chip?
Thanks a lot in advance for this
(here below I have just put a rough skeleton of the used code)

"
EGLDisplay eglDisplay = 0;
EGLSurface eglSurface = 0;
EGLint major, minor, num_configs;

..........
eglDisplay = eglGetDisplay(EGL_DEFAULT_DISPLAY));

eglInitialize(eglDisplay, &major, &minor);
eglBindAPI(EGL_OPENGL_ES_API);

eglChooseConfig(eglDisplay, configAttribs, &eglConfig, 1, &num_configs);

eglSurface = eglCreateWindowSurface(eglDisplay, eglConfig, NULL, NULL);
eglContext = eglCreateContext(eglDisplay, eglConfig, NULL, contextAttribs)));
eglMakeCurrent(eglDisplay, eglSurface, eglSurface, eglContext);
...........
...........


egl_setup(&eglDisplay,&eglSurface);


GLuint framebuffer;
GLuint depthRenderbuffer;
GLuint texture;

.....

glGenFramebuffers(1, &framebuffer);
glGenRenderbuffers(1, &depthRenderbuffer);
glGenTextures(1, &texture);
glBindTexture(GL_TEXTURE_2D, texture);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, texWidth, texHeight, 0, GL_RGB, GL_UNSIGNED_SHORT_5_6_5, NULL);


glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);

glBindRenderbuffer(GL_RENDERBUFFER, depthRenderbuffer);
glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT16, texWidth, texHeight);

glBindFramebuffer(GL_FRAMEBUFFER, framebuffer);

glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, texture, 0);

glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, depthRenderbuffer);

Switch (glCheckFramebufferStatus(GL_FRAMEBUFFER))
{
case GL_FRAMEBUFFER_COMPLETE:
fprintf(stdout, "\n o Framebuffer Complete");
break;
......
}


GLCheckError(glClearColor(1.0f, 0.0f, 0.0f, 1.0f));
.....
eglSwapBuffers(eglDisplay, eglSurface);


// glBindFramebuffer(GL_FRAMEBUFFER,0);
.........

eglSwapBuffers(eglDisplay, eglSurface);
""


Many Thanks
Parents
  • Note: This was originally posted on 13th September 2011 at http://forums.arm.com

    Sorry, I just reviewed my other post and it was the same as the one in this thread. I'll elaborate on the 'other' problem here.


    Having sorted out the error, I'm still left with the same problem reported by the original poster in this thread. I can now render to the texture object without any complaints from OpenGL ES 2, but when I then attempt to use that texture to paint a polygon in a later operation it comes up black.

    In answer to your question regarding usage, I create the FBO and texture object at startup and bind them together. Periodically, I set the FBO as the target of the draw commands (glSetFramebuffer(xxx) ), draw into the texture, then set the draw target back to the default framebuffer (glSetFramebuffer(0)). At this point I call another draw command that uses my texture as an input. This draw command results in black anywhere that the texture should have been rendered.

    I do not unbind the FBO I created from the texture. Should I do this?

    The device I'm working with in this case is the Samsung Galaxy S 2.

    Last bit of info...I'm not attaching any renderbuffers, just the texture object created with no data.

    The example code I provided in the other posting should demostrate the problem.


    Cheers...

Reply
  • Note: This was originally posted on 13th September 2011 at http://forums.arm.com

    Sorry, I just reviewed my other post and it was the same as the one in this thread. I'll elaborate on the 'other' problem here.


    Having sorted out the error, I'm still left with the same problem reported by the original poster in this thread. I can now render to the texture object without any complaints from OpenGL ES 2, but when I then attempt to use that texture to paint a polygon in a later operation it comes up black.

    In answer to your question regarding usage, I create the FBO and texture object at startup and bind them together. Periodically, I set the FBO as the target of the draw commands (glSetFramebuffer(xxx) ), draw into the texture, then set the draw target back to the default framebuffer (glSetFramebuffer(0)). At this point I call another draw command that uses my texture as an input. This draw command results in black anywhere that the texture should have been rendered.

    I do not unbind the FBO I created from the texture. Should I do this?

    The device I'm working with in this case is the Samsung Galaxy S 2.

    Last bit of info...I'm not attaching any renderbuffers, just the texture object created with no data.

    The example code I provided in the other posting should demostrate the problem.


    Cheers...

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