It looks like llvmpipe has real MSAA with NIR. Marek
On Wed, Jan 6, 2021 at 5:06 AM Jose Fonseca <jfons...@vmware.com> wrote: > That's an interesting idea! > > llvmpipe rasterization is complicated and very optimized, so changing > llvmpipe's rasterizer to spit out MSAA coverages is very hard. I think > that a good way to approach this is to: > > 1) continue to do single sample rasterization, but adjust the line coeffs > of the triangles edges (in llvmpipe rasterizer code known as *plane > coefficients*) to do conservative rasterization (ie, so that any fragment > that intersects a triangle is covered) when MSAA is enabled. See > https://developer.nvidia.com/content/dont-be-conservative-conservative-rasterization > > 2) once inside the fragment shader, compute SampleMaskIn from the > unadjusted vertex positions, using the desired number of samples (and > corresponding sample pattern) > > None of this would be throwaway work: the SampleMaskIn are correct and could > be used for full MSAA support in the future too, and the conservative > rasterization could be a feature on its own right too eventually. > > Jose > > ------------------------------ > *From:* mesa-dev <mesa-dev-boun...@lists.freedesktop.org> on behalf of > Marek Olšák <mar...@gmail.com> > *Sent:* Wednesday, January 6, 2021 05:57 > *To:* Brian Paul <bri...@vmware.com> > *Cc:* mesa-dev@lists.freedesktop.org <mesa-dev@lists.freedesktop.org>; > mesa-us...@lists.freedesktop.org <mesa-us...@lists.freedesktop.org> > *Subject:* Re: [Mesa-dev] Fwd: [Mesa-users] Issues with removal of > classic OSMesa > > Hi, > > llvmpipe could implement line and polygon smoothing by rasterizing in MSAA > and passing the coverage to SampleMaskIn in the fragment shader, but doing > Z/S tests and color writes and everything else single-sampled. Then, > FragColor.a *= bitcount(SampleMaskIn) / (float)num_samples. It's roughly > what OpenGL requires. There is at least one other gallium driver that does > that. > > Marek > > On Mon, Jan 4, 2021 at 3:02 PM Brian Paul <bri...@vmware.com> wrote: > > Hi Andreas, > > I'm forwarding your message to the mesa-dev list for better visibility. > > BTW, when you say "antialiasing" below, what exactly do you mean? > > -Brian > > > -------- Forwarded Message -------- > Subject: [Mesa-users] Issues with removal of classic OSMesa > Date: Thu, 31 Dec 2020 12:56:04 +0100 > From: Andreas Fänger <a.faen...@e-sign.com> > To: mesa-us...@lists.freedesktop.org > > Hi, > > I've just seen that classic OSMesa has been removed (again) from Mesa3D > a few weeks ago with this commit "mesa: Retire classic OSMesa". > > We are still actively using classical OSMesa for high quality rendering > of still images in a headless environment with no GPU support > (server-based rendering on windows and linux) > > Unfortunately, none of the alternative software renderers provide all > the features that we require, which is antialiasing and anisotropic > filtering. The current state is (correct me if I'm wrong) > > * softpipe: anisotropic filtering is supported, no antialiasing > > * llvmpipe: no anisotropic filtering, has MSAA > > * openswr: no anisotropic filtering, has MSAA, no OSMesa interface (?) > > We had hoped that classical OSMesa is only removed when there is a full > replacement after the discussions in 2016 when OSMesa was about to be > removed for the first time > > https://lists.freedesktop.org/archives/mesa-dev/2016-March/109665.html > <https://nam04.safelinks.protection.outlook.com/?url=https%3A%2F%2Flists.freedesktop.org%2Farchives%2Fmesa-dev%2F2016-March%2F109665.html&data=04%7C01%7Cjfonseca%40vmware.com%7C38811048f7d4434b32cc08d8b208137f%7Cb39138ca3cee4b4aa4d6cd83d9dd62f0%7C0%7C0%7C637455095057094583%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=HjIWy%2B4Mip6TkKYWUEuix41bPSgHUzZqgzwnBnjtBWA%3D&reserved=0> > > https://lists.freedesktop.org/archives/mesa-users/2016-March/001132.html > <https://nam04.safelinks.protection.outlook.com/?url=https%3A%2F%2Flists.freedesktop.org%2Farchives%2Fmesa-users%2F2016-March%2F001132.html&data=04%7C01%7Cjfonseca%40vmware.com%7C38811048f7d4434b32cc08d8b208137f%7Cb39138ca3cee4b4aa4d6cd83d9dd62f0%7C0%7C0%7C637455095057094583%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=nSZ3ZSfFRt8Z06avVzILOg4TipMkZ9CLyGMONcOkZxk%3D&reserved=0> > > and the commit that reverted the removal > > > http://cgit.freedesktop.org/mesa/mesa/commit/?id=9601815b4be886f4d92bf74916de98f3bdb7275c > <https://nam04.safelinks.protection.outlook.com/?url=http%3A%2F%2Fcgit.freedesktop.org%2Fmesa%2Fmesa%2Fcommit%2F%3Fid%3D9601815b4be886f4d92bf74916de98f3bdb7275c&data=04%7C01%7Cjfonseca%40vmware.com%7C38811048f7d4434b32cc08d8b208137f%7Cb39138ca3cee4b4aa4d6cd83d9dd62f0%7C0%7C0%7C637455095057104572%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=DufgWCKsN0v1nvTnT9VmyRkTSWiksioEYKIabLO%2BDvI%3D&reserved=0> > > Are there any plans to enhance the renderers so that at least one of > them is providing both anisotropic filtering and antialiasing? > > As far as I know, anisotropic texture filtering is also one of the > OpenGL 4.6 requirements. > > In 2016 I was told that there are only very few developers involved in > llvmpipe and that chances are not high that someone is going to port the > softpipe anisotropic filtering implementation as llvmpipe is much more > complex. Is there any change in that situation? > > If there are no such plans, is there any chance of reverting this commit > again so that classical OSMesa is available for windows and linux in > mesa >20? > > Regards, > > Andreas Fänger > > _______________________________________________ > mesa-dev mailing list > mesa-dev@lists.freedesktop.org > https://lists.freedesktop.org/mailman/listinfo/mesa-dev > <https://nam04.safelinks.protection.outlook.com/?url=https%3A%2F%2Flists.freedesktop.org%2Fmailman%2Flistinfo%2Fmesa-dev&data=04%7C01%7Cjfonseca%40vmware.com%7C38811048f7d4434b32cc08d8b208137f%7Cb39138ca3cee4b4aa4d6cd83d9dd62f0%7C0%7C0%7C637455095057104572%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=kU2Sz0FyTbVjirPOPsjm6hGVjJJuLg5qeCB93NnNuJk%3D&reserved=0> > >
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