64K/128K Specular Map Blue Marble Next Generation VT PNG !

LotharS · Post #81by **LotharS** » 20.10.2006, 08:37

cartrite wrote:to compress dds files with nvdxt the format options -dxt1c, dxt3 or dxt5 is what is compressing them. dxt5 has the best compression i think. -u888 is no compression.
dds will have larger file sizes than png but png files are rendered slower. If your trying to save diskspace the format to use would be jpg.

Ok, I just read the thread about dds files by The Singing Badger et. al.
I think I now understand my misconception. Typical case of assuming before reading :wink:

I appreciate all your efforts to enlighten me.

LoneHiker · Post #82by **LoneHiker** » 21.10.2006, 05:54

DXT1 compression ratios are 6:1 to 8:1
DXT3/DXT5 compression ratios are 4:1

The doubling of size you were getting between DXT1 and DXT3 is normal.

BTW, I found out certain older Nvidia cards (mine included) have an issue with DXT1 in that only 16-bit color precision is used (instead of 32-bit). This would explain why I'm seeing dithering artifacts in flat ocean color areas. The color used for these areas is not within the range of colors available at 16-bit so dithering is used with two or more colors to approximate the 32-bit color.

This bug isn't present with DXT3/DXT5.

Lone