Hi,
I remembered you had previous mentioned about the debug build of nvtt so I did
check that. I was also having some issues with building from source and using
static libs for nvtt so I ended up switching to the pre-build binaries from the
Nvidia web site just to be sure I wasn't breaking something at my end. Using
either my own release build or the pre-built binaries the results were the same
(as I posted before).
I have now completed the changes need to be able to switch at runtime between
the different techniques and have done a quick test of vpbmaster generating 6
levels of blue marble data from an ecw file. In this test the run using the GL
compressor finished in 17.7 seconds while the nvtt run took 90 seconds. I
wonder if this could be a platform difference? Maybe the GL drivers under Linux
do the compression in software while the windows ones do it in hardware.
Regarding submitting these changes, I have had a quick look at what
modifications I have made and while they aren't huge, they have been made on
top of the various outstanding submissions for VPB. Would you prefer me to hold
off with this submission until you have gone through the others individually (I
will handle and merges on my end) or should I just submit the combination of my
and Fabiens changes as I have them?
I have named the options:
--compressor-nvtt (nvvt, cuda if available) --compressor-nvtt-nocuda (force no
cuda) --compressor-gl-driver (current method)
which match to new build option 'compressionMethod':
enum CompressionMethod{ GL_DRIVER, NVTT,NVTT_NOCUDA }
Let me know if you can think of better names.
Cheers,
Brad
-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Robert Osfield
Sent: Tuesday, 26 October 2010 8:57 PM
To: OpenSceneGraph Users
Subject: Re: [osg-users] Proposed changes to VPB re compression
Hi Brad,
When I first tested the NVTT based compression on my Linux system I
found that the NVTT compression was slower than GL based. I then
checked the build options of NVTT and the Release build was set,
fixing this and then a rebuilding NVTT improved the results so they
matched the GL compile time.
As for the idea of having the -texture-process command line option to
select which to use, I think this is a good idea. #if'defing the code
paths for when NVTT isn't available is a perfectly acceptable thing to
do in this instance as we aren't talking about lots of place in the
code.
Cheers,
Robert.
On Tue, Oct 26, 2010 at 12:00 PM, Christiansen, Brad
<[email protected]> wrote:
> Hi,
>
> I have just finished some basic benchmarking of the three different
> compression methods I am playing with with some very surprising results (to
> me anyway : ) I created a small test app that used either the current GL
> context, NVTT with CUDA or vanilla CPU based NVTT to compress an image to a
> specified format. The image was compressed ten times and the total time taken
> is given in seconds. I ran the tests on two machines (one laptop and one
> desktop).
>
> Desktop Win7 3.2ghz CPU Geforce GTX275
> --------------------------------------
> CPU CUDA GL
> DXT1 17.0 1.47 0.66
> DXT1a 14.22 0.47
> DXT3 12.58 1.48 0.52
>
>
> Laptop Win7 3.17ghz CPU ATI Mobility FireGL V5700
> -------------------------------------------------
> CPU GL
> DXT1 18.61 3.913
> DXT1a 20.65 3.948
> DXT3 18.13 0.977
>
>
> The main surprise for me was how much faster using the current GL approach is
> compared to using NVTT. There is a big difference between the two video cards
> but both are much faster than the CPU. I was a bit disappointed at the CUDA
> results especially given this will only work on Nvidia cards and some formats
> (the DXT1a cuda score isn't given as this output format doesn't support cuda
> acceleration atm).
>
>
> Before these tests I was leaning towards defaulting to using NVTT for maximum
> compatibility but this doesn't look so good now.
>
> Cheers,
> Brad
>
>
>
>
>
>
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