Get the absolute GPU time in nanoseconds.
Time elapsed in nanoseconds since the OpenGL context was fully realized.
Examples
Get the current GPU time in seconds:
timeInSeconds = getAbsTimeGPU() * 1e-9
Get the GPU time elapsed:
t0 = getAbsTimeGPU()
# some drawing commands here ...
t1 = getAbsTimeGPU()
timeElapsed = (t1 - t0) * 1e-9 # take difference, convert to seconds