Anuj Phogat
46737cebd3
_mesa_meta_setup_blit_shader() currently generates a fragment shader
which, irrespective of the number of draw buffers, writes the color
to only one 'out' variable. Current shader rely on an undefined
behavior and possibly works by chance.
From OpenGL 4.0 spec, page 256:
"If a fragment shader writes to gl_FragColor, DrawBuffers specifies a
set of draw buffers into which the single fragment color defined by
gl_FragColor is written. If a fragment shader writes to gl_FragData,
or a user-defined varying out variable, DrawBuffers specifies a set
of draw buffers into which each of the multiple output colors defined
by these variables are separately written. If a fragment shader writes
to none of gl_FragColor, gl_FragData, nor any user defined varying out
variables, the values of the fragment colors following shader execution
are undefined, and may differ for each fragment color."
OpenGL 4.4 spec, page 463, added an additional line in this section:
"If some, but not all user-defined output variables are written, the
values of fragment colors corresponding to unwritten variables are
similarly undefined."
V2: Write color output to gl_FragColor instead of writing to multiple
'out' variables. This'll avoid recompiling the shader every time
draw buffers count is updated.
Cc: <mesa-stable@lists.freedesktop.org>
Signed-off-by: Anuj Phogat <anuj.phogat@gmail.com>
Reviewed-by: Matt Turner <mattst88@gmail.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
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 osmesa mesagdi to build classic mesa Windows GDI drivers; or 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 http://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.