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opengl-esantialiasing

Anti-aliasing techniques for OpenGL ES profiles

I've been investigating and trialling different AA techniques in OpenGL on both desktop and ES profiles ( es 2.0 & above ) for rendering 2D content to offscreen FBOs.

So far I've tried FSAA, FXAA, MSAA, and using the GL_LINE_SMOOTH feature.

I've not been able to find an adequate AA solution for ES profiles, where I've been limited to FSAA and FXAA because of API limitations. For example glTexImage2DMultisample ( required for MSAA ) and GL_LINE_SMOOTH functionality are unavailable.

FXAA is clever but blurs text glyphs to the point it's doing more harm than good, its only really suited to 3D scenes.

FSAA gives really good results particularly at 2x super-sampling but consumes too much extra video memory for me to use on most of our hardware.

I'm asking if anyone else has had much luck with any other techniques in similar circumstances - i.e: rendering anti-aliased 2D content to off-screen FBOs using an OpenGL ES profile.

Please note: I know I can ask for multi-sampling of the default frame buffer when setting up the window via GL_MULTISAMPLE on an ES profule, but this is no good to me rendering into off-screen FBOs where AA must be implemented oneself.

If any of my above statements are incorrect then please do jump in & put me straight, it may help!

Thank you.

Solution

  • For example glTexImage2DMultisample ( required for MSAA )

    Why is it required? To do this "within spec" render to a multi-sample storage buffer, and then use glBlitFramebuffer to resolve it to a single sampled surface.

    If you don't mind extensions then many vendors implement this extensions which behaves like an EGL window surface, with an implicit resolve, which is more efficient than the above as it avoids the round-trip to memory on tile-based hardware architectures.

    https://www.khronos.org/registry/gles/extensions/EXT/EXT_multisampled_render_to_texture.txt

    and GL_LINE_SMOOTH functionality are unavailable.

    Do you have a compelling use case for lines? If you really need them then just triangulate them, but for 3D content where MSAA really helps lines are really not commonly used.