Add support for ETC texture compression

[omcfadde]

No description provided.

[kkszysiu]

I started implementing support for ETC1 texture compression. Made a little script to build pk4 file with etc1 textures made from original tga's located on Doom 3 pk4 files.

Sadly it's not working as expected for now. I will push my changes soon.

Great that ETC2 textures compression is comming on GLES 3.0.

[kkszysiu]

https://github.com/kkszysiu/idtech4tgatoetc1/

Script to convert tga's from pk4's to pkm (format used by etc1 texture) :)

If anyone wants to use that script, please remember that you need to copy all pk4 files into ./paks/ directory, please also remember that you need to adjust paths in those variables:

scriptdir = "/home/kkszysiu/doom3tgatoetc1/"
sdkdir = "/home/kkszysiu/Pobrane/android-sdk-linux/"
imagemagickdir = "/home/kkszysiu/Dokumenty/imagemagick/bin/" # leave blank if default

To your needs.

Hope it helps.