Direct3D 11.1's target-independent rasterization (TIR) equivalent in OpenGL (including extensions)

Question

Target-independent rasterization (TIR) is a new hardware feature in DirectX 11.1, which Microsoft used to improve Direct2D in Windows 8. AMD claimed that TIR improved performance in 2D vector graphics by some 500%. And there was some "war of words" with Nvidia's because Kepler GPUs apparently don't support TIR (among other DirectX 11.1 features). The idea of TIR appears to have originated at Microsoft, because they have a patent application for it.

Now Direct2D is fine your OS is Windows, but is there some OpenGL (possibly vendor/AMD) extension that provides access to the same hardware/driver TIR thing? I think AMD is in a bit of a weird spot because there is no vendor-independent 2D vector graphics extension for OpenGL; only Nvidia is promoting NV_path_rendering for now and its architecture is rather different from Direct2D. So it's unclear where anything made by AMD to accelerate 2D vector graphics can plug (or show up) in OpenGL, unlike in the Direct2D+Direct3D world. I hope I my pessimism is going to be unraveled by a simple answer below.

I'm actually posting an update of sorts here because there's not enough room in comment-style posts for this. There seems to be a little confusion as to what TIR does, which is not simply "a framebuffer with no storage attached". This might be because I've only linked above to the mostly awful patentese (which is however the most detailed document I could find on TIR). The best high-level overview of TIR I found is the following snippet from Sinofsky's blog post:

to improve performance when rendering irregular geometry (e.g. geographical borders on a map), we use a new graphics hardware feature called Target Independent Rasterization, or TIR.

TIR enables Direct2D to spend fewer CPU cycles on tessellation, so it can give drawing instructions to the GPU more quickly and efficiently, without sacrificing visual quality. TIR is available in new GPU hardware designed for Windows 8 that supports DirectX 11.1.

Below is a chart showing the performance improvement for rendering anti-aliased geometry from a variety of SVG files on a DirectX 11.1 GPU supporting TIR: [chart snipped]

We worked closely with our graphics hardware partners [read AMD] to design TIR. Dramatic improvements were made possible because of that partnership. DirectX 11.1 hardware is already on the market today and we’re working with our partners to make sure more TIR-capable products will be broadly available.

It's this bit of hardware I'm asking to use from OpenGL. (Heck, I would settle even for invoking it from Mantle, because that also will be usable outside of Windows.)

Answer 1

The OpenGL equivalent of TIR is EXT_raster_multisample.

It's mentioned in the new features page for Nvidia's Maxwell architecture: https://developer.nvidia.com/content/maxwell-gm204-opengl-extensions.

Answer 2

I believe TIR is just a repurposing of a feature nvidia and AMD use for antialiasing.

Nvidia calls it coverage sample antialiasing and their gl extensions is GL_NV_framebuffer_multisample_coverage.

AMD calls it EQAA but they don't seem to have a gl extension.