Kenneth Graunke
74e1d6e20c
Older OpenGL defines two equations for converting from signed-normalized
to floating point data. These are:
f = (2c + 1)/(2^b - 1) (equation 2.2)
f = max{c/2^(b-1) - 1), -1.0} (equation 2.3)
Both OpenGL 4.2+ and OpenGL ES 3.0+ mandate that equation 2.3 is to be
used in all scenarios, and remove equation 2.2. DirectX uses equation
2.3 as well. Intel hardware only supports equation 2.3, so Gen7.5+
systems that use the vertex fetcher hardware to do the conversions
always get formula 2.3.
This can make a big difference for 10-10-10-2 formats - the 2-bit value
can represent 0 with equation 2.3, and cannot with equation 2.2.
Ivybridge and older were using equation 2.2 for OpenGL, and 2.3 for ES.
Now that Ivybridge supports OpenGL 4.2, this is wrong - we need to use
the new rules, at least in core profile. That would leave Gen4-6 doing
something different than all other hardware, which seems...lame.
With context version promotion, applications that requested a pre-4.2
context may get promoted to 4.2, and thus get the new rules. Zero cases
have been reported of this being a problem. However, we've received a
report that following the old rules breaks expectations. SuperTuxKart
apparently renders the cars red when following equation 2.2, and works
correctly when following equation 2.3:
https://github.com/supertuxkart/stk-code/issues/2885#issuecomment-353858405
So, this patch deletes the legacy equation 2.2 support entirely, making
all hardware and APIs consistently use the new equation 2.3 rules.
If we ever find an application that truly requires the old formula, then
we'd likely want that application to work on modern hardware, too. We'd
likely restore this support as a driconf option. Until then, drop it.
This commit will regress Piglit's draw-vertices-2101010 test on
pre-Haswell without the corresponding Piglit patch to accept either
formula (commit 35daaa1695ea01eb85bc02f9be9b6ebd1a7113a1):
draw-vertices-2101010: Accept either SNORM conversion formula.
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Chris Forbes <chrisforbes@google.com>
File: docs/README.WIN32 Last updated: 21 June 2013 Quick Start ----- ----- Windows drivers are build with SCons. Makefiles or Visual Studio projects are no longer shipped or supported. Run scons libgl-gdi to build gallium based GDI driver. This will work both with MSVS or Mingw. Windows Drivers ------- ------- At this time, only the gallium GDI driver is known to work. Source code also exists in the tree for other drivers in src/mesa/drivers/windows, but the status of this code is unknown. Recipe ------ Building on windows requires several open-source packages. These are steps that work as of this writing. - install python 2.7 - install scons (latest) - install mingw, flex, and bison - install pywin32 from here: http://www.lfd.uci.edu/~gohlke/pythonlibs get pywin32-218.4.win-amd64-py2.7.exe - install git - download mesa from git see https://www.mesa3d.org/repository.html - run scons General ------- After building, you can copy the above DLL files to a place in your PATH such as $SystemRoot/SYSTEM32. If you don't like putting things in a system directory, place them in the same directory as the executable(s). Be careful about accidentially overwriting files of the same name in the SYSTEM32 directory. The DLL files are built so that the external entry points use the stdcall calling convention. Static LIB files are not built. The LIB files that are built with are the linker import files associated with the DLL files. The si-glu sources are used to build the GLU libs. This was done mainly to get the better tessellator code. If you have a Windows-related build problem or question, please post to the mesa-dev or mesa-users list.