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multiple FBOs bug

Started by BloodLust666 Apr 26, 2010 at 5:06 PM 4 replies 800+ views

Original Post

Apr 26, 2010 at 5:06 PM

I'm not sure what's going on but I have one FBO rendering a scene to a texture, then taking that texture, texturing a quad and rendering that to another texture, then taking that texture and rendering it finally to the screen. It seems, though, that at the beginning of my simulation the window flashes once on what objects are to be rendering but then goes black... It may have to do with ordering on rendering, but I didn't think it did. The only time I'm clearing the texture is right before having to render to it again, so I don't understand why my screen would be black

karwosts

Apr 26, 2010 at 5:09 PM

I think we're going to need to see some code to help you out, what you described sounds feasible enough.

This is probably more appropriate for the opengl forum anyway, as this sounds pretty API specific.

BloodLust666

Apr 26, 2010 at 5:16 PM

oh oops, sorry, can this can be moved to openGL please :) thanks

There's a lot of actual code though and a lot of OO-ness... Maybe pseudo code could work?

foreach RenderTarget  bindTarget  foreach Camera rendering to this target    SetViewport    glClear    RenderScene      foreach Object        foreach Material attached to object          bindTexture          render VBO  glDrawBuffers

That's essentially how I have my engine structure.

karwosts

Apr 26, 2010 at 5:26 PM

Quote:

Maybe pseudo code could work?

Not promising that I myself can help you, but I'm going to guess that this isn't going to be enough. 90% of these issues come down to an incorrect API call, so I think you're going to at least need to get some real code down on the screen.

BloodLust666

Apr 26, 2010 at 5:37 PM

foreach RenderTarget  glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, m_bufferID); // m_bufferID is 0 if window  foreach Camera rendering to this target    glViewport(m_viewport.left, m_viewport.top, m_viewport.width, m_viewport.height);    glScissor(m_viewport.left, m_viewport.top, m_viewport.width, m_viewport.height);    glClearColor(m_clearColor.x, m_clearColor.y, m_clearColor.z, m_clearColor.w);    glClearDepth(1.0f);    glClearStencil(0);    glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT );    RenderScene      foreach Object        foreach Material attached to object          glBindTexture(GL_TEXTURE_2D, m_id); // some of these could be render targets          render VBO  glDrawBuffers( m_bufferList.size(), &m_bufferList[0]);

I'm about 99% certain my FBOs are set up correctly because when I use only 2 rendertargets (the window, and a render texture) everything looks fine. The scene is rendered to the texture, then the texture is rendered to the screen just fine. As soon as I re-direct that texture to render to another texture, and then how THAT second texture render to the screen is when nothing shows up except for the first frame.

BloodLust666

Apr 26, 2010 at 8:44 PM

ummmm, so I definitely have this working now... NO idea why it didn't work before. All I simply did was create a VERY simple shader that basically just passed the same data along and now it works perfectly. Any idea why this is the case? Or should I just conclude that the fixed pipeline sucks. heh :P

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