/** @page required-extensions Functionality requiring specific OpenGL version or extensions
@brief List of functions not available on OpenGL 2.1 / OpenGL ES 2.

The engine is meant to be run on OpenGL 3 capable hardware, but most of the
functionality is working in OpenGL 2.1 hardware too (i.e. integrated Intel
GPUs), unless stated otherwise. OpenGL ES is also supported, see @ref building
for guide how to build the engine for it.

Following are lists of functionality requiring specific OpenGL version. In
most cases it is also specified which extension is required for given
functionality, so if given hardware supports required extension, it doesn't
need to have required OpenGL version too (e.g. `APPLE_vertex_array_object` is
supported on Intel GPUs even if they are capable of OpenGL 2.1 only).

- @subpage requires-gl
- @subpage requires-gl30
- @subpage requires-gl31
- @subpage requires-gl32
- @subpage requires-gl33
- @subpage requires-gl40
- @subpage requires-gl41
- @subpage requires-gl42
- @subpage requires-gl43
- @subpage requires-extension
- @subpage requires-gles30
- @subpage requires-es-extension

@page requires-gl Functionality requiring desktop OpenGL (not available on OpenGL ES)
@page requires-gl30 Functionality requiring OpenGL 3.0
@page requires-gl31 Functionality requiring OpenGL 3.1
@page requires-gl32 Functionality requiring OpenGL 3.2
@page requires-gl33 Functionality requiring OpenGL 3.3
@page requires-gl40 Functionality requiring OpenGL 4.0
@page requires-gl41 Functionality requiring OpenGL 4.1
@page requires-gl42 Functionality requiring OpenGL 4.2
@page requires-gl43 Functionality requiring OpenGL 4.3
@page requires-extension Functionality requiring specific OpenGL extension
@page requires-gles30 Functionality requiring OpenGL ES 3.0
@page requires-es-extension Functionality requiring specific OpenGL ES extension

*/