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

Mikhail I. Izmestev izmmishao5 at gmail.com
Thu Apr 14 05:43:11 PDT 2011


14.04.2011 16:34, Mikhail I. Izmestev wrote:
> 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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Mikhail
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