glMapBufferOES returns null, but no error is generated

[Mohs3n]

Hi,
I'm trying to implement a game using ndk. I use glMapBufferOES to
update buffer data. However, the function returns NULL and 0 is
returned by glGetError(which means no error is generated by opengl).
Could this be a bug? Has anyone been able to use this function?

[alan]

glMapBufferOES is an extension, have you checked your devices extension support? i believe that if you call an unsupported extension there are no guarantees of the behaviour (will probably just crash instantly)

[Mohs3n]

Thanks for your reply,
Is there any way to check if an extension is supported during run-time?

[alan]

yes using the standard opengl extension mechanism:

glGetString(GL_EXTENSIONS)

[Mohs3n]

Yeah. It's not supported. The problem was that I thought glMapBuffer
is included in vertex_buffer_object extension (which is on pc version
of opengl). But, on opengl es it's in a different extension called
GL_OES_mapbuffer.

[Ferm]

Hello

I have also run into this now trying to port a game from iPhone. Using
nexus one, which does not have the GL_OES_mapbuffer extension, it
returns NULL.

How do you get around this?

Thank you for any pointers.

[Louise Cypher]

just dont use glMapBuffer ... ;)

nexus one (and the whole snapdragon family) is very tricky with dynamic buffers, since the glBufferSubData call is enormously _slow_ and instead you need to use glBufferData witch is counter-intuitive and

have very bad performance on hummingbird processors (galaxy/galaxy tab) (but they support glMapBuffer)

so basically you need some abstraction layer around your index/vertex buffers to pack all this and tetect whatever you are on adreno or on sgx

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