glReadBuffer vs glReadBufferNV in OpenGL ES 2.0 -

I am trying to create OpenSceneGraph 3.2 for the Ubuntu armhf architecture, but I receive a compilation error about a symbol I am getting it The symbol in the question is glReadBuffer . I looked at the GLES2 / gl2.h header, and in fact, that symbol is not there, however, the symbol is present in the GLES3 / gl3.h , and tells the document online That function was added in OpenGL ES 3.0. However, I found a function named glReadBufferNV in the form called GLES2 / gl2ext.h (which is not #include in the source files.

I think that glReadBufferNV can be used in place of glReadBuffer , and possibly a side effect. I suspect that NV stands for Nvidia, and that it is only Nvidia implementation. Is that correct? If so, then get the glReadBuffer in OpenGL ES 2.0 E way is OpenCGraph can be created under OpenGL ES 2.0, this impression?

Edit: As it has been found, create this part of OpenCA graph while creating with OpenGL or OpenGL 3.0 The code going out was excluded. However, I can see the glReadBufferNV .

Interested in what's special about, as your research suggests, for Glyph Buffer 3.0 A was added to the ES, it has not been defined in 2.0. Before that, the editor file you got, an extension defined glReadBufferNV - specifically.

So what's happened is that there was nothing in the imagination, at least Nvidya thought it would be useful, so he implemented the 'OpenGL Extension', which was later discussed in Khronos, all The ones with shore matters or ambiguities and have finally made their way into the core space.

How does this generally occur in the development process of GL: Extension is not yet in the main library, come together to provide functionality, if appropriate, they are discussed and refined and original Specialties are adopted.

Comparing with the extension documentation, there are some links in the other extensions of the extension that you see it as a basic imagery (eg COLOR_ATTACHMENTi_NV as a source) but see the solution issue 7 :

The version 6 of this specification is not compatible with OpenGL 3.0 ES. For references without a back buffer, this extension makes FRONT the default read buffer. Instead of calling it back to ES 3.0, how can it be reconciled?

Resolve: Update the specification to match the ES 3.0 behavior. It introduces one of the back discrepancies, but some apps are likely to be affected. In EGL ecosystem where ES 2.0 is prevalent, only pixmaps have no backbuffers and their usage is not limited.

So the extension has been revised in the past so that it agrees with the original idea.