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I think the point was that the OpenGL framebuffer is ultimately a 2D space. Whatever your input data and computation model, at the end of the data the output from your computation goes into a set of arrays with two index coordinates. That's a fairly specious point, maybe, but it's not wrong.

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But surely since the memory that the frame buffer is encoded into is 1D, OpenGL is really one-dimensional. /s

Sure, the frame buffer is 2D in the end - it has to be, in order to display on a standard computer monitor - but surely the fact that OpenGL is able to natively handle point data as 3D-homogeneous coordinates, and support for techniques like depth buffering out of the box counts for more than any argument that only really amounts to "after it is finished doing all its work you just have a 2D image".

Sure, ultimately most rendering is about producing 2D images as output. But the whole OpenGL pipeline is designed around taking 3D data, and providing abstractions to enable that rendering. Rasterization and depth sorting are only one piece of the rendering pipeline. Of course it's also possible to drop the z coordinates, or use orthogonal projections, to use OpenGL in a purely 2D way. Plenty of applications do that, but that doesn't make the API 2D. It just makes the use case 2D.

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