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Vincent_M

OpenGL Framebuffer Objects [OpenGL]

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[font=arial, verdana, tahoma, sans-serif][size=2]I'm trying to get FBOs to work with my game engine. So far, I'm using my FBO to render to a texture, and then use my sprite batch class to render the texture as a sprite. Unfortunately, my texture is invisible. I've checked to see if the framebuffer and texture for my render target were both created, and everything looks good. I also check to see if my sprite batch rendering method isn't failing somewhere in the rendering cycle. Everything checks out.

Here's my render target constructor that sets everything up:
[code]

RenderTarget::RenderTarget(int width, int height) : Texture2D()
{
Initialize();
this->width = width;
this->height = height;

// setup the new framebuffer
int oldFBO = GetCurrentFBO();
glGenFramebuffers(1, &fbo);
SetBoundFBO(fbo);

// setup the color texture attachment
glGenTextures(1, &name);
SetBoundTexture(GL_TEXTURE_2D, name);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA8, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, minFilter);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, magFilter);
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, name, 0);

// check render target status
int status = glCheckFramebufferStatus(GL_FRAMEBUFFER);
if(status != GL_FRAMEBUFFER_COMPLETE)
printf("ERROR: render target failed to create FBO\n");

// reset the the last FBO used
SetBoundFBO(oldFBO);
loaded = true;
}
[/code]

Here's Set/GetBoundFBO:
[code]

int SetBoundFBO(unsigned int name)
{
// return early if the FBO is already in use
if(framebufferObject == name)
return 0;

// set the new FBO
glBindFramebuffer(GL_FRAMEBUFFER, framebufferObject);
return 1;
}


int GetCurrentFBO()
{ return framebufferObject; }
[/code]

Those functions are global functions that help monitor FBO is currently being used without the overhead of setting/getting the FBO with unnecessary OpenGL calls (necessary on iOS platforms). How does this code look so far? My goal is to write some render target code that allows me to compile this on Windows, Mac, and iOS devices.

EDIT: I'd like to point out that my render target is 800x800 texture if that makes any difference.[/size][/font]

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I think I solved the issue to my problem. I wasn't rendering anything to the screen! There were some other inconsistencies I found when reading through an OpenGL ES 2.0 book. This book is where I'm getting most of my GLES 2.0 information since this code is supposed to meet those standards first. Either way, most practices (if not all by now) are supported by OpenGL, and are really efficient from what I've encountered so far. Just to recap, the code that works is this:
[code]

RenderTarget::RenderTarget(int width, int height) : Texture2D()
{
Initialize();
this->width = width;
this->height = height;

// generate the new buffers
glGenFramebuffers(1, &fbo);
glGenTextures(1, &name);
glGenRenderbuffers(1, &depthRenderbuffer);

// set the current buffers
int oldFBO = GetCurrentFBO();
SetBoundFBO(fbo);
SetBoundTexture(GL_TEXTURE_2D, name);
glBindRenderbuffer(GL_RENDERBUFFER, depthRenderbuffer);

// setup the color texture attachment
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, width, height, 0, GL_RGB, GL_UNSIGNED_BYTE, NULL);
SetFilter(GL_TEXTURE_MAG_FILTER, GL_LINEAR);
SetFilter(GL_TEXTURE_MIN_FILTER, GL_LINEAR);
SetWrapMode(GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
SetWrapMode(GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, name, 0);

// setup the framebuffer
glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT16, width, height);
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, name, 0);
glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, depthRenderbuffer);

// check render target status
int status = glCheckFramebufferStatus(GL_FRAMEBUFFER);
if(status != GL_FRAMEBUFFER_COMPLETE)
printf("ERROR: render target failed to create FBO\n");
SetBoundFBO(oldFBO);
loaded = true;
}
[/code]

You will see some wrapper functions in there such as SetBoundFBO(), GetBoundFBO(), etc. As mentioned previously, those are just used to optimize out any unnecessary GL-calls that can be costly on some platforms. If anyone would like me to post my GL state manager, I can do that. Keep in mind that it doesn't fully support everything I'd like --just the really common stuff I've come across in my experiences.

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Btw, do FBOs have to be a power of 2? I ask because I'm getting a border around the top and right of my sprite that displays the rendered texture.

For example, my window is 800x800 pixels, and so is my texture. Right now, I'm rendering the entire texture to a fullscreen sprite to see if everything matches up. It looks like if I make my render target texture larger than 400x400, everything gets clipped past the 400x400 margin in the top and right. Do my textures have to be power of 2? I've tried that, and I get the same results. Also, things don't match up. The aspect ratio is 1.0 for everything, and nothing ever changes either.

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[quote name='Vincent_M' timestamp='1311546962' post='4839763']
Btw, do FBOs have to be a power of 2? I ask because I'm getting a border around the top and right of my sprite that displays the rendered texture.

For example, my window is 800x800 pixels, and so is my texture. Right now, I'm rendering the entire texture to a fullscreen sprite to see if everything matches up. It looks like if I make my render target texture larger than 400x400, everything gets clipped past the 400x400 margin in the top and right. Do my textures have to be power of 2? I've tried that, and I get the same results. Also, things don't match up. The aspect ratio is 1.0 for everything, and nothing ever changes either.
[/quote]

I fixed all of that. Turns out that my window was 480x480, and for some odd reason I was using 800x800 for everything else (ortho setup, render texture, etc). I have two defines that define my window width and height, and I pass that down to all my game states and use them now. It all works!

Now, I'm onto post-processing, and I've run into an interesting bug with simple blur. For some reason, pixels on the sides of my screen are blurring with the pixels on the other side even though my wrap modes are strictly GL_CLAMP_TO_EDGE.

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