Hi,
It appears that within texture.cpp in core OSG library, glTexImage2D is
faster than glCompressedTexImage2D by about 80 - 100%.
glTexImage2D is used when the texture data is uncompressed (e.g. RGB24) and
glCompressedTexImage2D is used when the texture data is compressed (e.g.
S3DXT1).
I have time the execution on both Nvidia GPU and Intel HD4000 graphics. The
timing difference is similar when using compressed and uncompressed. I have
only profile this on Windows platform using the latest NVIDIA and Intel
drivers. For NVIDIA driver, I have specifically enable full graphics
performance using its control panel. In addition, I have tried to compile my
texture with NVTT and it gives the same performance close to S3DXT1.
I will like to understand on why compressed data takes longer to load onto
GPU whereas uncompressed data performance is better.
Will appreciate if somebody can enlighten me on this. Thanks in advance.
Kind Regards,
Boon Wah
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http://forum.openscenegraph.org/viewtopic.php?p=58616#58616
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