The recreation of the tutorial skybox sample from the Skybox (2D) with Terragen and Skypaint - Advanced article on the Valve Developer Community Wiki, now for use in any Half-Life 2 mod.
Had to create a bottom skybox texture as the original shown here didn't have it.
Credit goes to Jochum Skoglund who made the Tempest Envmap skybox texture.
Tempest_Envmap_Sample_Skybox__.zip
Key Authors
Wadmooddeer
N/A
Version
Unknown