+Advanced command line usage
+===========================
+
+
+Dump GL state at a particular call
+----------------------------------
+
+You can get a dump of the bound GL state at call 12345 by doing:
+
+ /path/to/glretrace -D 12345 application.trace > 12345.json
+
+This is precisely the mechanism the GUI obtains its own state.
+
+You can compare two state dumps with the jsondiff.py script:
+
+ ./scripts/jsondiff.py 12345.json 67890.json
+
+
+Comparing two traces side by side
+---------------------------------
+
+ ./scripts/tracediff.sh trace1.trace trace2.trace
+
+This works only on Unices, and it will truncate the traces due to performance
+limitations.
+
+
+Recording a video with FFmpeg
+-----------------------------
+
+You can make a video of the output by doing
+
+ /path/to/glretrace -s - application.trace \
+ | ffmpeg -r 30 -f image2pipe -vcodec ppm -i pipe: -vcodec mpeg4 -y output.mp4
+
+
+Advanced usage for OpenGL implementors
+======================================
+
+There are several avanced usage examples meant for OpenGL implementors.
+
+
+Regression testing
+------------------
+
+These are the steps to create a regression testsuite around apitrace:
+
+* obtain a trace
+
+* obtain reference snapshots, by doing:
+
+ mkdir /path/to/snapshots/
+ /path/to/glretrace -s /path/to/reference/snapshots/ application.trace
+
+ on reference system.
+
+* prune the snapshots which are not interesting
+
+* to do a regression test, do:
+
+ /path/to/glretrace -c /path/to/reference/snapshots/ application.trace
+
+ Alternatively, for a HTML summary, use the snapdiff script:
+
+ /path/to/glretrace -s /path/to/current/snapshots/ application.trace
+ ./scripts/snapdiff.py --output summary.html /path/to/reference/snapshots/ /path/to/current/snapshots/
+
+
+Automated git-bisection
+-----------------------
+
+With tracecheck.py it is possible to automate git bisect and pinpoint the
+commit responsible for a regression.
+
+Below is an example of using tracecheck.py to bisect a regression in the
+Mesa-based Intel 965 driver. But the procedure could be applied to any GL
+driver hosted on a git repository.
+
+First, create a build script, named build-script.sh, containing:
+
+ #!/bin/sh
+ set -e
+ export PATH=/usr/lib/ccache:$PATH
+ export CFLAGS='-g'
+ export CXXFLAGS='-g'
+ ./autogen.sh --disable-egl --disable-gallium --disable-glut --disable-glu --disable-glw --with-dri-drivers=i965
+ make clean
+ make "$@"
+
+It is important that builds are both robust, and efficient. Due to broken
+dependency discovery in Mesa's makefile system, it was necessary invoke `make
+clean` in every iteration step. `ccache` should be installed to avoid
+recompiling unchanged source files.
+
+Then do:
+
+ cd /path/to/mesa
+ export LIBGL_DEBUG=verbose
+ export LD_LIBRARY_PATH=$PWD/lib
+ export LIBGL_DRIVERS_DIR=$PWD/lib
+ git bisect start \
+ 6491e9593d5cbc5644eb02593a2f562447efdcbb 71acbb54f49089b03d3498b6f88c1681d3f649ac \
+ -- src/mesa/drivers/dri/intel src/mesa/drivers/dri/i965/
+ git bisect run /path/to/tracecheck.py \
+ --precision-threshold 8.0 \
+ --build /path/to/build-script.sh \
+ --gl-renderer '.*Mesa.*Intel.*' \
+ --retrace=/path/to/glretrace \
+ -c /path/to/reference/snapshots/ \
+ topogun-1.06-orc-84k.trace
+
+The trace-check.py script will skip automatically when there are build
+failures.
+
+The `--gl-renderer` option will also cause a commit to be skipped if the
+`GL_RENDERER` is unexpected (e.g., when a software renderer or another GL
+driver is unintentianlly loaded due to missing symbol in the DRI driver, or
+another runtime fault).
+
+
+Side by side retracing
+----------------------
+
+In order to determine which draw call a regression first manifests one could
+generate snapshots for every draw call, using the -S option. That is, however,
+very inefficient for big traces with many draw calls.
+
+A faster approach is to run both the bad and a good GL driver side-by-side.
+The latter can be either a preivously known good build of the GL driver, or a
+reference software renderer.
+
+This can be achieved with retracediff.py script, which invokes glretrace with
+different environments, allowing to choose the desired GL driver by
+manipulating variables such as `LD_LIBRARY_PATH` or `LIBGL_DRIVERS_DIR`.
+
+For example:
+
+ ./scripts/retracediff.py \
+ --ref-env LD_LIBRARY_PATH=/path/to/reference/GL/implementation \
+ -r ./glretrace \
+ --diff-prefix=/path/to/output/diffs \
+ application.trace
+
+
+