[osg-users] OSG-3.6 breaking changes to GLES2 buffered objects

[Robert Osfield]

Hi Michael,

Thanks for the details.  I've started looking into the GLES2 specs,
and buffer object support is there, just one mention of vertex buffer
object and no mentions of pixel buffer objects.

Is sounds like GLExtensions.cpp just needs to be tweaked a bit to
properly enable/disable the correct features.

Robert.

On 23 March 2018 at 08:43, michael kapelko <kornerr at gmail.com> wrote:
> Hi.
> This is to continue the discussion of PR that broke web (Emscripten)
> builds: https://github.com/openscenegraph/OpenSceneGraph/pull/501
>
> The mentioned changes break rendering of the osgemscripten example
> (found in OpenSceneGraph/examples/osgemscripten).
> I've prepared two builds to depict the difference.
> 1. Build with the breaking fix:
> https://kornerr.github.io/osg-pbo-gles2-fix-builds/versions/fix/osgemscripten.html
> 2. Build with the breaking fix reverted:
> https://kornerr.github.io/osg-pbo-gles2-fix-builds/versions/reverted-fix/osgemscripten.html
>
> The second build simply has the following GLExtension.cpp line:
>   isBufferObjectSupported = isVBOSupported && isPBOSupported;
> replaced with:
>   isBufferObjectSupported = isVBOSupported;
>
> So the problem is not really in PBO support, but in the fact that
> possibly missing PBO support removes buffer object support. This is
> wrong. The osgemscripten example uses VBO and this is what WebGL1
> requires.
>
> You can build osgemscripten example yourself (README explains how to
> do it, it's easy on Linux) and see the errors.
> Make sure to use the updated CMakeLists.txt I've attached to this email.
>
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