[osg-users] DDS with DXT1 with and without alpha

Mikhail I. Izmestev izmmishao5 at gmail.com
Thu Apr 14 05:34:52 PDT 2011


14.04.2011 16:16, Robert Osfield wrote:

> The heart of the problem is that the DDS file format doesn't
> distiguish between the
> two varients of DXT1, there is an alpha bit in the DDS header that
> could be used,
> but 3rd party tools like nvdxt and nvcompress that write DDS files
> don't set this bit
> so both DTX1c with black encoded pixels and DTX1a are essentially identical
> in terms of header and content.

Where from this information?

$ nvdxt.exe -nomipmap -dxt1a -file test_dxt1.png -output test_dxt1a.dds
Version 8.30
     Reading test_dxt1.png  [Processing] Writing .\test_dxt1a.dds

$ nvdxt.exe -nomipmap -dxt1c -file test_dxt1.png -output test_dxt1c.dds
Version 8.30
     Reading test_dxt1.png  [Processing] Writing .\test_dxt1c.dds

$ md5sum.exe test_dxt1*.dds
ac1473f8822abbb2d6006de0021c6bc0 *test_dxt1a.dds
249071d0b0974593b310656acea73e1d *test_dxt1c.dds

Mikhail



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