README


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=== a simple benchmark to evaluate drawing time of points with high overdraw ===

Upon writing a benchmark to evaluate the cost of using various data types
for vertex attributes I notices a strange behaviour in drawing huge amounts
of blended point with lots of overdraw: The naive expectation would be, that
when drawing a constant amount of point the more fragments are touched, the
higher to overall draw time.

As it turns out for at least a NVidia GeForce GTX980 things are not that simple.
The drawing times actually reduce with increasing viewport size... or rather
increasing vertical size; the horizontal size doesn't seem to have that much
of an effect.

To gather data from more GPUs I provide this source code repository and ask
people to run the program with their GPUs and submit the results for evaluation.

**IMPORTANT NOTICE:**
_The program depends on OpenGL-4.3, namely compute shaders. However since this
is more or less a quick hack I didn't add any version or feature checking. So
if trying to run this program on a system that lacks OpenGL-4.3 the results
are undefined and may range from a black window with nonsensical numbers to
immediate program crashes!_

== Build Dependencies ==
- OpenGL headers and linker stubs
  - Windows: compiler toolchains should have them without extra effort
  - X11/GLX (Linux / *BSD / Solaris): if OpenGL drivers are installed, they
      should be available. Otherwise install the Mesa development support
      package.

- GLUT (kind of smells, but everybody dabbling with GPUs has it around)
- GLEW (kind of sucks, but everybody dabbling with GPUs has it around)

Parts of this program make use of C99 features (inline, NAN (defined in math.h))
so it must be built with a compiler that has sufficient support for C99. This
mostly affects the Microsoft Visual C++ toolchain, where the minimum requirement
is Visual C++ 2013.

== Build Instructions ==
- Using *make*: just run `make`
- Using *CMake*: `mkdir $BUILDDIR ; cd $BUILDDIR ; cmake $SOURCEDIR ; make`

== Run Instructions ==
Run the program and direct its stdout into a file, .e.g.

    ./pointoverdrawbench > statistics.log

OpenGL debug messages are emitted to stderr. If you see something noteworthy
there, add this to your report.

== How to report results ==
Submit them as a Github Issue