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<TITLE>Environment Variables</TITLE>

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<H1>Environment Variables</H1>

<p>
Mesa supports the following environment variables:
</p>
<ul>
<li>MESA_NO_ASM - if set, disables all assembly language optimizations
<li>MESA_NO_MMX - if set, disables Intel MMX optimizations
<li>MESA_NO_3DNOW - if set, disables AMD 3DNow! optimizations
<li>MESA_NO_SSE - if set, disables Intel SSE optimizations
<li>MESA_DEBUG - if set, error messages are printed to stderr.
If the value of MESA_DEBUG is "FP" floating point arithmetic errors will
generate exceptions.
<li>MESA_NO_DITHER - if set, disables dithering, overriding glEnable(GL_DITHER)
<li>MESA_TEX_PROG - if set, implement conventional texture env modes with
fragment programs (intended for developers only)
<li>MESA_TNL_PROG - if set, implement conventional vertex transformation
operations with vertex programs (intended for developers only).
Setting this variable automatically sets the MESA_TEX_PROG variable as well.
<li>MESA_EXTENSION_OVERRIDE - can be used to enable/disable extensions.
A value such as "GL_EXT_foo -GL_EXT_bar" will enable the GL_EXT_foo extension
and disable the GL_EXT_bar extension.
<li>MESA_GLSL - <a href="shading.html#envvars">shading language options</a>
</ul>

<p>
The following are only applicable to the Xlib software driver.
See the <A HREF="xlibdriver.html">Xlib software driver page</A> for details.
</p>
<ul>
<li>MESA_RGB_VISUAL - specifies the X visual and depth for RGB mode
<li>MESA_CI_VISUAL - specifies the X visual and depth for CI mode
<li>MESA_BACK_BUFFER - specifies how to implement the back color buffer,
    either "pixmap" or "ximage"
<li>MESA_GAMMA - gamma correction coefficients for red, green, blue channels
<li>MESA_XSYNC - enable synchronous X behavior (for debugging only)
<li>MESA_GLX_FORCE_CI - if set, force GLX to treat 8bpp visuals as CI visuals
<li>MESA_GLX_FX - set to either "fullscreen" for full-screen rendering,
  "window" to render into a window, or "disable" to disable the Glide driver.
<li>MESA_GLX_FORCE_ALPHA - if set, forces RGB windows to have an alpha channel.
<li>MESA_GLX_DEPTH_BITS - specifies default number of bits for depth buffer.
<li>MESA_GLX_ALPHA_BITS - specifies default number of bits for alpha channel.
</ul>


<p>
These environment variables are for the Intel i945/i965 drivers:
</p>
<ul>
<li>INTEL_STRICT_CONFORMANCE - if set to 1, enable sw fallbacks to improve
    OpenGL conformance.  If set to 2, always use software rendering.
<li>INTEL_NO_BLIT - if set, disable hardware-accelerated glBitmap,
    glCopyPixels, glDrawPixels.
</ul>


<p>
These environment variables are for the Radeon R300 driver:
</p>
<ul>
<li>R300_NO_TCL - if set, disable hardware-accelerated Transform/Clip/Lighting.
</ul>

<p>
Mesa EGL supports different sets of environment variables.  See the
<a href="egl.html">Mesa EGL</a> page for the details.
</p>

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