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

Mikhail I. Izmestev izmmishao5 at gmail.com
Thu Apr 14 06:06:14 PDT 2011


14.04.2011 16:43, Mikhail I. Izmestev пишет:
> 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
>
> Attach files to previous message.
>
> Mikhail

I'm sorry,
In DDS header really no alpha flag, my mistake :)

$ nvdxt.exe -nomipmap -alpha -dxt1a -file test_dxt1_a.png -output 
test_dxt1a_a.dds
Version 8.30
     Reading test_dxt1_a.png  [Processing] Writing .\test_dxt1a_a.dds

$ nvdxt.exe -nomipmap -dxt1c -alpha -file test_dxt1_a.png -output 
test_dxt1c_a.dds
Version 8.30
     Reading test_dxt1_a.png  [Processing] Writing .\test_dxt1c_a.dds

Mikhail.
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