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Signed-off-by: Tony Lofthouse <lofthous@amazon.com>
Increase texture and app window size

In order to observe the performance characteristics of the
apps different rendering modes give the renderer more work
to do.

On my desktop, I get:

PBO: off

Transfer Rate: 2126.9 MB/s. (33.2 FPS)
Transfer Rate: 2204.8 MB/s. (34.4 FPS)
Transfer Rate: 2161.9 MB/s. (33.8 FPS)
Transfer Rate: 2229.6 MB/s. (34.8 FPS)

PBO: 1

Transfer Rate: 2294.5 MB/s. (35.9 FPS)
Transfer Rate: 2305.2 MB/s. (36.0 FPS)
Transfer Rate: 2315.9 MB/s. (36.2 FPS)
Transfer Rate: 2319.7 MB/s. (36.2 FPS)

PBO: 2

Transfer Rate: 853.0 MB/s. (13.3 FPS)
Transfer Rate: 857.1 MB/s. (13.4 FPS)
Transfer Rate: 860.2 MB/s. (13.4 FPS)
Transfer Rate: 845.2 MB/s. (13.2 FPS)
Transfer Rate: 863.0 MB/s. (13.5 FPS)

We see a slight performance improvement using a single
PBO but performance drops when using two PBOs.

It's interesting that as pointed out on:
http://www.songho.ca/opengl/gl_pbo.html
in order not to stall until the GPU is done with
the PBO, a call to glBufferDataARB() with a NULL
argument is made. Without this the PBO 1 render
rate is ~14 FPS.

I'd speculate that the strategy of the application
discarding the PBO data is not ideal. So a future
experiment will try updating 2 PBOs from a thread.

Signed-off-by: Tony Lofthouse <lofthous@amazon.com>
Experiment with a thread updating two PBOs

By avoiding reallocating the PBOs and using a thread to
update the PBO contents we get a ~40% improvement in
performance.

transfer Rate: 3246.6 MB/s. (50.7 FPS)
Transfer Rate: 3176.7 MB/s. (49.6 FPS)
Transfer Rate: 2919.1 MB/s. (45.6 FPS)
Transfer Rate: 3025.1 MB/s. (47.3 FPS)
Transfer Rate: 3199.4 MB/s. (50.0 FPS)

Signed-off-by: Tony Lofthouse <lofthous@amazon.com>