Kenneth Graunke
2412c4c81e
The previous implementation of CLAMP() allowed NaN to pass through
unscathed, by failing both comparisons. NaN isn't exactly a value
between MIN and MAX, which can break the assumptions of many callers.
This patch changes CLAMP to convert NaN to MIN, arbitrarily. Callers
that need NaN to be handled in a specific manner should probably open
code something, or use a macro specifically designed to do that.
Section 2.3.4.1 of the OpenGL 4.5 spec says:
"Any representable floating-point value is legal as input to a GL
command that requires floating-point data. The result of providing a
value that is not a floating-point number to such a command is
unspecified, but must not lead to GL interruption or termination.
In IEEE arithmetic, for example, providing a negative zero or a
denormalized number to a GL command yields predictable results,
while providing a NaN or an infinity yields unspecified results."
While CLAMP may apply to more than just GL inputs, it seems reasonable
to follow those rules, and allow MIN as an "unspecified result".
This prevents assertion failures in i965 when running the games
"XCOM: Enemy Unknown" and "XCOM: Enemy Within", which call
glTexEnv(GL_TEXTURE_FILTER_CONTROL_EXT, GL_TEXTURE_LOD_BIAS_EXT,
-nan(0x7ffff3));
presumably unintentionally. i965 clamps the LOD bias to be in range,
and asserts that it's in the proper range when converting to fixed
point. NaN is not, so it crashed. We'd like to at least avoid that.
Reviewed-by: Roland Scheidegger <sroland@vmware.com>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.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.