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A legacy question


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#1 include4eto   Members   -  Reputation: 103

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Posted 28 March 2011 - 02:21 PM

Hi, everyone. As you might have noticed, I am new to GameDEV, so if i am posting this in a wrong section or doing anything not as supposed to be done please tell me.
My question is about a function i stumbled on while going through the ARB FBO documentation. The function in question is getRenderBufferImage (). Google yielded no results (apart from the aforementioned site), so i was hoping that someone has heard of it or perhaps even used it. If so, please give me a hint to what it did (as it is no longer supported, i think?).

P.P.: I am asking about this because this specific function i have to include in a report and since no one has heard of it i have hit quite a thick wall.

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#2 karwosts   Members   -  Reputation: 840

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Posted 28 March 2011 - 02:24 PM

Where exactly did you read about this? From the ARB FBO extension it looks like it never existed at all (was rejected by developers):

Features we have rejected include:

* GetRenderbufferImage (benefit/demand does not seem to
outweigh the additional complexity.)


My Projects:
Portfolio Map for Android - Free Visual Portfolio Tracker
Electron Flux for Android - Free Puzzle/Logic Game

#3 include4eto   Members   -  Reputation: 103

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Posted 28 March 2011 - 02:36 PM

Where exactly did you read about this? From the ARB FBO extension it looks like it never existed at all (was rejected by developers):


Features we have rejected include:

* GetRenderbufferImage (benefit/demand does not seem to
outweigh the additional complexity.)


It is exactly where i read it. Yet again, they mention demand which would suggest people actually wanted this function to exist. To what purpose?

#4 karwosts   Members   -  Reputation: 840

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Posted 28 March 2011 - 02:50 PM

I assume that someone may have wanted a method from which to extract pixel data from a renderbuffer. When drawing to an FBO channel you can either write to a texture or a renderbuffer, both being similar except that a renderbuffer can't be used as a texture, and may be simpler to implement as a tradeoff for not being able to use it as a texture, I'm not really sure.

If you really wanted to render to an FBO and retrieve pixel data, you could just as easily draw to a texture and get the pixels from that, so maybe that's why they decided not to have a dedicated function to retrieve renderbuffer data.
My Projects:
Portfolio Map for Android - Free Visual Portfolio Tracker
Electron Flux for Android - Free Puzzle/Logic Game

#5 include4eto   Members   -  Reputation: 103

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Posted 28 March 2011 - 03:01 PM

Thank you for the quick response. Seems quite logical to remove such a function (or not write it in the first place) so i'll go with that in my repost. Besides, i was considering making up something about pixel data anyway.

#6 V-man   Members   -  Reputation: 805

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Posted 28 March 2011 - 05:41 PM

I assume that someone may have wanted a method from which to extract pixel data from a renderbuffer. When drawing to an FBO channel you can either write to a texture or a renderbuffer, both being similar except that a renderbuffer can't be used as a texture, and may be simpler to implement as a tradeoff for not being able to use it as a texture, I'm not really sure.

If you really wanted to render to an FBO and retrieve pixel data, you could just as easily draw to a texture and get the pixels from that, so maybe that's why they decided not to have a dedicated function to retrieve renderbuffer data.


You don't need to render to a texture and get pixels from the texture.
Render to the render buffer and use glReadPixels.
Sig: http://glhlib.sourceforge.net
an open source GLU replacement library. Much more modern than GLU.
float matrix[16], inverse_matrix[16];
glhLoadIdentityf2(matrix);
glhTranslatef2(matrix, 0.0, 0.0, 5.0);
glhRotateAboutXf2(matrix, angleInRadians);
glhScalef2(matrix, 1.0, 1.0, -1.0);
glhQuickInvertMatrixf2(matrix, inverse_matrix);
glUniformMatrix4fv(uniformLocation1, 1, FALSE, matrix);
glUniformMatrix4fv(uniformLocation2, 1, FALSE, inverse_matrix);




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