14 jaren geleden · c60eb632b7
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 <LI><A HREF="mangling.html" target="MainFrame">Function Name Mangling</A>
 <LI><A href="llvmpipe.html" target="MainFrame">Gallium llvmpipe driver</A>
 <LI><A href="postprocess.html" target="MainFrame">Gallium post-processing</A>
 <LI><A href="viewperf.html" target="MainFrame">Viewperf Issues</A>
 </ul>

 <b>Developer Topics</b>
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 <TITLE>Viewperf Issues</TITLE>

 <link rel="stylesheet" type="text/css" href="mesa.css"></head>

 <BODY>

 <h1>Viewperf Issues</h1>

 <p>
 This page lists known issues with
 <a href="http://www.spec.org/gwpg/gpc.static/vp11info.html" target="_main">SPEC Viewperf 11</a>
 when running on Mesa-based drivers.
 </p>

 <p>
 The Viewperf data sets are basically GL API traces that are recorded from
 CAD applications, then replayed in the Viewperf framework.
 </p>

 <p>
 The primary problem with these traces is they blindly use features and
 OpenGL extensions that were supported by the OpenGL driver when the trace
 was recorded,
 but there's no checks to see if those features are supported by the driver
 when playing back the traces with Viewperf.
 </p>

 <p>
 These issues have been reported to the SPEC organization in the hope that
 they'll be fixed in the future.
 </p>



 <h2>Catia-03 tests 3, 4, 8</h2>

 <p>
 These tests use features of the
 <a href="http://www.opengl.org/registry/specs/NV/fragment_program2.txt"
 target="_main">
 GL_NV_fragment_program2</a> and
 <a href="http://www.opengl.org/registry/specs/NV/vertex_program3.txt"
 target="_main">
 GL_NV_vertex_program3</a> extensions without checking if the driver supports
 them.
 </p>
 <p>
 When Mesa tries to compile the vertex/fragment programs it generates errors
 (which Viewperf ignores).
 Subsequent drawing calls become no-ops and the rendering is incorrect.
 </p>



 <h2>sw-02 tests 1, 2, 4</h2>

 <p>
 These tests depend on the
 <a href="http://www.opengl.org/registry/specs/NV/primitive_restart.txt"
 target="_main">GL_NV_primitive_restart</a> extension.
 </p>

 <p>
 If the Mesa driver doesn't support this extension the rendering will
 be incorrect and the test will fail.
 </p>


 <h2>Lightwave-01 test 3</h2>

 <p>
 This test uses a number of mipmapped textures, but the textures are
 incomplete because the last/smallest mipmap level (1 x 1 pixel) is
 never specified.
 </p>

 <p>
 A trace captured with
 <a href="https://github.com/apitrace/apitrace" target="_main">API trace</a>
 shows this sequences of calls like this:

 <pre>
 2504 glBindTexture(target = GL_TEXTURE_2D, texture = 55)
 2505 glTexImage2D(target = GL_TEXTURE_2D, level = 0, internalformat = GL_RGBA, width = 512, height = 512, border = 0, format = GL_RGB, type = GL_UNSIGNED_SHORT, pixels = blob(1572864))
 2506 glTexImage2D(target = GL_TEXTURE_2D, level = 1, internalformat = GL_RGBA, width = 256, height = 256, border = 0, format = GL_RGB, type = GL_UNSIGNED_SHORT, pixels = blob(393216))
 2507 glTexImage2D(target = GL_TEXTURE_2D, level = 2, internalformat = GL_RGBA, width = 128, height = 128, border = 0, format = GL_RGB, type = GL_UNSIGNED_SHORT, pixels = blob(98304))
 [...]
 2512 glTexImage2D(target = GL_TEXTURE_2D, level = 7, internalformat = GL_RGBA, width = 4, height = 4, border = 0, format = GL_RGB, type = GL_UNSIGNED_SHORT, pixels = blob(96))
 2513 glTexImage2D(target = GL_TEXTURE_2D, level = 8, internalformat = GL_RGBA, width = 2, height = 2, border = 0, format = GL_RGB, type = GL_UNSIGNED_SHORT, pixels = blob(24))
 2514 glTexParameteri(target = GL_TEXTURE_2D, pname = GL_TEXTURE_MIN_FILTER, param = GL_LINEAR_MIPMAP_LINEAR)
 2515 glTexParameteri(target = GL_TEXTURE_2D, pname = GL_TEXTURE_WRAP_S, param = GL_REPEAT)
 2516 glTexParameteri(target = GL_TEXTURE_2D, pname = GL_TEXTURE_WRAP_T, param = GL_REPEAT)
 2517 glTexParameteri(target = GL_TEXTURE_2D, pname = GL_TEXTURE_MAG_FILTER, param = GL_NEAREST)
 </pre>

 <p>
 Note that one would expect call 2514 to be glTexImage(level=9, width=1,
 height=1) but it's not there.
 </p>

 <p>
 The minification filter is GL_LINEAR_MIPMAP_LINEAR and the texture's
 GL_TEXTURE_MAX_LEVEL is 1000 (the default) so a full mipmap is expected.
 </p>

 <p>
 Later, these incomplete textures are bound before drawing calls.
 According to the GL specification, if a fragment program or fragment shader
 is being used, the sampler should return (0,0,0,1) ("black") when sampling
 from an incomplete texture.
 This is what Mesa does and the resulting rendering is darker than it should
 be.
 </p>

 <p>
 It appears that NVIDIA's driver (and possibly AMD's driver) detects this case
 and returns (1,1,1,1) (white) which causes the rendering to appear brighter
 and match the reference image (however, AMD's rendering is <em>much</em>
 brighter than NVIDIA's).
 </p>

 <p>
 If the fallback texture created in _mesa_get_fallback_texture() is
 initialized to be full white instead of full black the rendering appears
 correct.
 However, we have no plans to implement this work-around in Mesa.

 </p>


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