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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 15th November 2010 at http://forums.arm.com

    ...And you say that final pass where you render out onto the video surface is coming up blank.

    In an earlier post you said that it came up blank when you had a framebuffer bound with glBindFramebuffer(GL_FRAMEBUFFER, framebuffer), but not when you first called glBindFramebuffer(GL_FRAMEBUFFER, 0).

    This is because if you don't unbind the framebuffer with glBindFramebuffer(GL_FRAMEBUFFER, 0), it tries to render onto the currently bound frame buffer, not to the video surface.

    I suppose the question I should be asking is, why do you want to keep the framebuffer bound? After you've attached it to a texture, the only reason to keep a framebuffer bound is to render to it.

    -Stacy
Reply
  • Note: This was originally posted on 15th November 2010 at http://forums.arm.com

    ...And you say that final pass where you render out onto the video surface is coming up blank.

    In an earlier post you said that it came up blank when you had a framebuffer bound with glBindFramebuffer(GL_FRAMEBUFFER, framebuffer), but not when you first called glBindFramebuffer(GL_FRAMEBUFFER, 0).

    This is because if you don't unbind the framebuffer with glBindFramebuffer(GL_FRAMEBUFFER, 0), it tries to render onto the currently bound frame buffer, not to the video surface.

    I suppose the question I should be asking is, why do you want to keep the framebuffer bound? After you've attached it to a texture, the only reason to keep a framebuffer bound is to render to it.

    -Stacy
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