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OpenGL's dual color blending feature was specified so that an implementation could support both multiple render targets (MRT) and dual source blending. Fragment shader outputs specify both "location" (the render target number) and "index" (either color 0 or 1). I believe DirectX only has the notion of "location" - if using dual color blending, location 0 or 1 will specify the operands. If not, then location means the render target index. The two features can't be used together. As such, some applications mistakenly try to use <loc = 0, index = 0> and <loc = 1, index = 0> in a shader used for dual color blending with a single render target, rather than the correct <loc = 0, index = 0> and <loc = 0, index = 1>. In particular, Unigine Heaven 4.0 and Valley 1.0 suffer from this bug. Unigine is aware of the problem, and quickly developed a fix, but has not bothered to change the download link on their website to a working copy in over a year. People were still using the broken version and complaining. We tried working around this by disabling dual color blending, but that apparently hurts performance, and people were once again unhappy. On i965, dual source blending is achieved by using different framebuffer write messages than normal rendering. So, we have to compile different code for the two cases. We're not being pedantic: we actually have to know in order to function. Normally, dual source blending is detectable in the shader: if a shader has an output with index = 1, then it's meant for blending, not MRT. With the broken inputs, they're indistinguishable, so we can only tell by looking at the current GL state. This patch implements a new drirc workaround: export dual_color_blend_by_location=true which makes the i965 driver detect when OpenGL state is configured for dual source blending, and recompile the fragment shader to use the right messages. In that case, we allow either location = 1 or index = 1 to specify the second source for the blending equations. It also re-enables GL_ARB_blend_func_extended for Unigine. Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=92233 Signed-off-by: Kenneth Graunke <kenneth@whitecape.org> Reviewed-by: Marek Olšák <marek.olsak@amd.com> Reviewed-by: Iago Toral Quiroga <itoral@igalia.com> Reviewed-by: Ian Romanick <ian.d.romanick@intel.com> Acked-by: Ilia Mirkin <imirkin@alum.mit.edu> |
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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 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.